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remoteproc.txt: standardize document format
Each text file under Documentation follows a different format. Some doesn't even have titles! Change its representation to follow the adopted standard, using ReST markups for it to be parseable by Sphinx: - mark document and section titles; - adjust identation; - mark literal blocks Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Mauro Carvalho Chehab
Jonathan Corbet
parent
ce0f95a501
commit
620b470bb4
@ -1,6 +1,9 @@
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==========================
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Remote Processor Framework
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==========================
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1. Introduction
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Introduction
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============
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Modern SoCs typically have heterogeneous remote processor devices in asymmetric
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multiprocessing (AMP) configurations, which may be running different instances
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@ -26,44 +29,62 @@ remoteproc will add those devices. This makes it possible to reuse the
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existing virtio drivers with remote processor backends at a minimal development
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cost.
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2. User API
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User API
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========
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::
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int rproc_boot(struct rproc *rproc)
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- Boot a remote processor (i.e. load its firmware, power it on, ...).
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If the remote processor is already powered on, this function immediately
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returns (successfully).
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Returns 0 on success, and an appropriate error value otherwise.
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Note: to use this function you should already have a valid rproc
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handle. There are several ways to achieve that cleanly (devres, pdata,
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the way remoteproc_rpmsg.c does this, or, if this becomes prevalent, we
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might also consider using dev_archdata for this).
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Boot a remote processor (i.e. load its firmware, power it on, ...).
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If the remote processor is already powered on, this function immediately
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returns (successfully).
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Returns 0 on success, and an appropriate error value otherwise.
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Note: to use this function you should already have a valid rproc
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handle. There are several ways to achieve that cleanly (devres, pdata,
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the way remoteproc_rpmsg.c does this, or, if this becomes prevalent, we
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might also consider using dev_archdata for this).
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::
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void rproc_shutdown(struct rproc *rproc)
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- Power off a remote processor (previously booted with rproc_boot()).
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In case @rproc is still being used by an additional user(s), then
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this function will just decrement the power refcount and exit,
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without really powering off the device.
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Every call to rproc_boot() must (eventually) be accompanied by a call
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to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
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Notes:
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- we're not decrementing the rproc's refcount, only the power refcount.
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which means that the @rproc handle stays valid even after
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rproc_shutdown() returns, and users can still use it with a subsequent
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rproc_boot(), if needed.
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Power off a remote processor (previously booted with rproc_boot()).
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In case @rproc is still being used by an additional user(s), then
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this function will just decrement the power refcount and exit,
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without really powering off the device.
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Every call to rproc_boot() must (eventually) be accompanied by a call
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to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
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.. note::
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we're not decrementing the rproc's refcount, only the power refcount.
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which means that the @rproc handle stays valid even after
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rproc_shutdown() returns, and users can still use it with a subsequent
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rproc_boot(), if needed.
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::
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struct rproc *rproc_get_by_phandle(phandle phandle)
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- Find an rproc handle using a device tree phandle. Returns the rproc
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handle on success, and NULL on failure. This function increments
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the remote processor's refcount, so always use rproc_put() to
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decrement it back once rproc isn't needed anymore.
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3. Typical usage
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Find an rproc handle using a device tree phandle. Returns the rproc
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handle on success, and NULL on failure. This function increments
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the remote processor's refcount, so always use rproc_put() to
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decrement it back once rproc isn't needed anymore.
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#include <linux/remoteproc.h>
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Typical usage
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=============
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/* in case we were given a valid 'rproc' handle */
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int dummy_rproc_example(struct rproc *my_rproc)
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{
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::
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#include <linux/remoteproc.h>
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/* in case we were given a valid 'rproc' handle */
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int dummy_rproc_example(struct rproc *my_rproc)
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{
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int ret;
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/* let's power on and boot our remote processor */
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@ -80,84 +101,111 @@ int dummy_rproc_example(struct rproc *my_rproc)
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/* let's shut it down now */
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rproc_shutdown(my_rproc);
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}
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}
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4. API for implementors
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API for implementors
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====================
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::
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struct rproc *rproc_alloc(struct device *dev, const char *name,
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const struct rproc_ops *ops,
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const char *firmware, int len)
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- Allocate a new remote processor handle, but don't register
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it yet. Required parameters are the underlying device, the
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name of this remote processor, platform-specific ops handlers,
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the name of the firmware to boot this rproc with, and the
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length of private data needed by the allocating rproc driver (in bytes).
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This function should be used by rproc implementations during
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initialization of the remote processor.
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After creating an rproc handle using this function, and when ready,
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implementations should then call rproc_add() to complete
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the registration of the remote processor.
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On success, the new rproc is returned, and on failure, NULL.
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Allocate a new remote processor handle, but don't register
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it yet. Required parameters are the underlying device, the
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name of this remote processor, platform-specific ops handlers,
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the name of the firmware to boot this rproc with, and the
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length of private data needed by the allocating rproc driver (in bytes).
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Note: _never_ directly deallocate @rproc, even if it was not registered
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yet. Instead, when you need to unroll rproc_alloc(), use rproc_free().
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This function should be used by rproc implementations during
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initialization of the remote processor.
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After creating an rproc handle using this function, and when ready,
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implementations should then call rproc_add() to complete
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the registration of the remote processor.
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On success, the new rproc is returned, and on failure, NULL.
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.. note::
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**never** directly deallocate @rproc, even if it was not registered
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yet. Instead, when you need to unroll rproc_alloc(), use rproc_free().
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::
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void rproc_free(struct rproc *rproc)
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- Free an rproc handle that was allocated by rproc_alloc.
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This function essentially unrolls rproc_alloc(), by decrementing the
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rproc's refcount. It doesn't directly free rproc; that would happen
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only if there are no other references to rproc and its refcount now
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dropped to zero.
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Free an rproc handle that was allocated by rproc_alloc.
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This function essentially unrolls rproc_alloc(), by decrementing the
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rproc's refcount. It doesn't directly free rproc; that would happen
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only if there are no other references to rproc and its refcount now
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dropped to zero.
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::
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int rproc_add(struct rproc *rproc)
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- Register @rproc with the remoteproc framework, after it has been
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allocated with rproc_alloc().
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This is called by the platform-specific rproc implementation, whenever
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a new remote processor device is probed.
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Returns 0 on success and an appropriate error code otherwise.
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Note: this function initiates an asynchronous firmware loading
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context, which will look for virtio devices supported by the rproc's
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firmware.
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If found, those virtio devices will be created and added, so as a result
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of registering this remote processor, additional virtio drivers might get
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probed.
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Register @rproc with the remoteproc framework, after it has been
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allocated with rproc_alloc().
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This is called by the platform-specific rproc implementation, whenever
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a new remote processor device is probed.
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Returns 0 on success and an appropriate error code otherwise.
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Note: this function initiates an asynchronous firmware loading
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context, which will look for virtio devices supported by the rproc's
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firmware.
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If found, those virtio devices will be created and added, so as a result
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of registering this remote processor, additional virtio drivers might get
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probed.
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::
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int rproc_del(struct rproc *rproc)
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- Unroll rproc_add().
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This function should be called when the platform specific rproc
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implementation decides to remove the rproc device. it should
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_only_ be called if a previous invocation of rproc_add()
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has completed successfully.
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After rproc_del() returns, @rproc is still valid, and its
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last refcount should be decremented by calling rproc_free().
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Unroll rproc_add().
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Returns 0 on success and -EINVAL if @rproc isn't valid.
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This function should be called when the platform specific rproc
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implementation decides to remove the rproc device. it should
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_only_ be called if a previous invocation of rproc_add()
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has completed successfully.
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After rproc_del() returns, @rproc is still valid, and its
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last refcount should be decremented by calling rproc_free().
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Returns 0 on success and -EINVAL if @rproc isn't valid.
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::
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void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type)
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- Report a crash in a remoteproc
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This function must be called every time a crash is detected by the
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platform specific rproc implementation. This should not be called from a
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non-remoteproc driver. This function can be called from atomic/interrupt
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context.
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5. Implementation callbacks
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Report a crash in a remoteproc
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This function must be called every time a crash is detected by the
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platform specific rproc implementation. This should not be called from a
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non-remoteproc driver. This function can be called from atomic/interrupt
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context.
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Implementation callbacks
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========================
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These callbacks should be provided by platform-specific remoteproc
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drivers:
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drivers::
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/**
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* struct rproc_ops - platform-specific device handlers
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* @start: power on the device and boot it
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* @stop: power off the device
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* @kick: kick a virtqueue (virtqueue id given as a parameter)
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*/
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struct rproc_ops {
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/**
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* struct rproc_ops - platform-specific device handlers
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* @start: power on the device and boot it
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* @stop: power off the device
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* @kick: kick a virtqueue (virtqueue id given as a parameter)
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*/
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struct rproc_ops {
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int (*start)(struct rproc *rproc);
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int (*stop)(struct rproc *rproc);
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void (*kick)(struct rproc *rproc, int vqid);
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};
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};
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Every remoteproc implementation should at least provide the ->start and ->stop
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handlers. If rpmsg/virtio functionality is also desired, then the ->kick handler
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@ -179,7 +227,8 @@ the exact virtqueue index to look in is optional: it is easy (and not
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too expensive) to go through the existing virtqueues and look for new buffers
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in the used rings.
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6. Binary Firmware Structure
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Binary Firmware Structure
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=========================
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At this point remoteproc only supports ELF32 firmware binaries. However,
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it is quite expected that other platforms/devices which we'd want to
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@ -207,43 +256,43 @@ resource entries that publish the existence of supported features
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or configurations by the remote processor, such as trace buffers and
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supported virtio devices (and their configurations).
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The resource table begins with this header:
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The resource table begins with this header::
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/**
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* struct resource_table - firmware resource table header
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* @ver: version number
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* @num: number of resource entries
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* @reserved: reserved (must be zero)
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* @offset: array of offsets pointing at the various resource entries
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*
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* The header of the resource table, as expressed by this structure,
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* contains a version number (should we need to change this format in the
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* future), the number of available resource entries, and their offsets
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* in the table.
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*/
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struct resource_table {
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/**
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* struct resource_table - firmware resource table header
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* @ver: version number
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* @num: number of resource entries
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* @reserved: reserved (must be zero)
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* @offset: array of offsets pointing at the various resource entries
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*
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* The header of the resource table, as expressed by this structure,
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* contains a version number (should we need to change this format in the
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* future), the number of available resource entries, and their offsets
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* in the table.
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*/
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struct resource_table {
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u32 ver;
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u32 num;
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u32 reserved[2];
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u32 offset[0];
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} __packed;
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} __packed;
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Immediately following this header are the resource entries themselves,
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each of which begins with the following resource entry header:
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each of which begins with the following resource entry header::
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/**
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* struct fw_rsc_hdr - firmware resource entry header
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* @type: resource type
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* @data: resource data
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*
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* Every resource entry begins with a 'struct fw_rsc_hdr' header providing
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* its @type. The content of the entry itself will immediately follow
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* this header, and it should be parsed according to the resource type.
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*/
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struct fw_rsc_hdr {
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/**
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* struct fw_rsc_hdr - firmware resource entry header
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* @type: resource type
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* @data: resource data
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*
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* Every resource entry begins with a 'struct fw_rsc_hdr' header providing
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* its @type. The content of the entry itself will immediately follow
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* this header, and it should be parsed according to the resource type.
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*/
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struct fw_rsc_hdr {
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u32 type;
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u8 data[0];
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} __packed;
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} __packed;
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Some resources entries are mere announcements, where the host is informed
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of specific remoteproc configuration. Other entries require the host to
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@ -252,32 +301,32 @@ is expected, where the firmware requests a resource, and once allocated,
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the host should provide back its details (e.g. address of an allocated
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memory region).
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Here are the various resource types that are currently supported:
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Here are the various resource types that are currently supported::
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/**
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* enum fw_resource_type - types of resource entries
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*
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* @RSC_CARVEOUT: request for allocation of a physically contiguous
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* memory region.
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* @RSC_DEVMEM: request to iommu_map a memory-based peripheral.
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* @RSC_TRACE: announces the availability of a trace buffer into which
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* the remote processor will be writing logs.
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* @RSC_VDEV: declare support for a virtio device, and serve as its
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* virtio header.
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* @RSC_LAST: just keep this one at the end
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*
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* Please note that these values are used as indices to the rproc_handle_rsc
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* lookup table, so please keep them sane. Moreover, @RSC_LAST is used to
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* check the validity of an index before the lookup table is accessed, so
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* please update it as needed.
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*/
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enum fw_resource_type {
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/**
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* enum fw_resource_type - types of resource entries
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*
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* @RSC_CARVEOUT: request for allocation of a physically contiguous
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* memory region.
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* @RSC_DEVMEM: request to iommu_map a memory-based peripheral.
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* @RSC_TRACE: announces the availability of a trace buffer into which
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* the remote processor will be writing logs.
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* @RSC_VDEV: declare support for a virtio device, and serve as its
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* virtio header.
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* @RSC_LAST: just keep this one at the end
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*
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* Please note that these values are used as indices to the rproc_handle_rsc
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* lookup table, so please keep them sane. Moreover, @RSC_LAST is used to
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* check the validity of an index before the lookup table is accessed, so
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* please update it as needed.
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*/
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enum fw_resource_type {
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RSC_CARVEOUT = 0,
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RSC_DEVMEM = 1,
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RSC_TRACE = 2,
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RSC_VDEV = 3,
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RSC_LAST = 4,
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};
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};
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For more details regarding a specific resource type, please see its
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dedicated structure in include/linux/remoteproc.h.
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@ -286,7 +335,8 @@ We also expect that platform-specific resource entries will show up
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at some point. When that happens, we could easily add a new RSC_PLATFORM
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type, and hand those resources to the platform-specific rproc driver to handle.
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7. Virtio and remoteproc
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Virtio and remoteproc
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=====================
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The firmware should provide remoteproc information about virtio devices
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that it supports, and their configurations: a RSC_VDEV resource entry
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