mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-11-27 03:55:37 +08:00
drm/doc: vblank cleanup
Unify and review everything, plus make sure it's all correct markup. Drop the kernel-doc for internal functions. Also rework the overview section, it's become rather outdated. Unfortuantely the kernel-doc in drm_driver isn't rendered yet, but that will change as soon as drm_driver is kernel-docified properly. Also document properly that drm_vblank_cleanup is optional, the core calls this already. v2: Make it clear that cleanup happens in drm_dev_fini for drivers with their own ->release callback (Thierry). Acked-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170524145212.27837-11-daniel.vetter@ffwll.ch
This commit is contained in:
Daniel Vetter
parent
27fa5510f1
commit
57d30230c5
@ -551,60 +551,8 @@ various modules/drivers.
|
||||
Vertical Blanking
|
||||
=================
|
||||
|
||||
Vertical blanking plays a major role in graphics rendering. To achieve
|
||||
tear-free display, users must synchronize page flips and/or rendering to
|
||||
vertical blanking. The DRM API offers ioctls to perform page flips
|
||||
synchronized to vertical blanking and wait for vertical blanking.
|
||||
|
||||
The DRM core handles most of the vertical blanking management logic,
|
||||
which involves filtering out spurious interrupts, keeping race-free
|
||||
blanking counters, coping with counter wrap-around and resets and
|
||||
keeping use counts. It relies on the driver to generate vertical
|
||||
blanking interrupts and optionally provide a hardware vertical blanking
|
||||
counter. Drivers must implement the following operations.
|
||||
|
||||
- int (\*enable_vblank) (struct drm_device \*dev, int crtc); void
|
||||
(\*disable_vblank) (struct drm_device \*dev, int crtc);
|
||||
Enable or disable vertical blanking interrupts for the given CRTC.
|
||||
|
||||
- u32 (\*get_vblank_counter) (struct drm_device \*dev, int crtc);
|
||||
Retrieve the value of the vertical blanking counter for the given
|
||||
CRTC. If the hardware maintains a vertical blanking counter its value
|
||||
should be returned. Otherwise drivers can use the
|
||||
:c:func:`drm_vblank_count()` helper function to handle this
|
||||
operation.
|
||||
|
||||
Drivers must initialize the vertical blanking handling core with a call
|
||||
to :c:func:`drm_vblank_init()` in their load operation.
|
||||
|
||||
Vertical blanking interrupts can be enabled by the DRM core or by
|
||||
drivers themselves (for instance to handle page flipping operations).
|
||||
The DRM core maintains a vertical blanking use count to ensure that the
|
||||
interrupts are not disabled while a user still needs them. To increment
|
||||
the use count, drivers call :c:func:`drm_vblank_get()`. Upon
|
||||
return vertical blanking interrupts are guaranteed to be enabled.
|
||||
|
||||
To decrement the use count drivers call
|
||||
:c:func:`drm_vblank_put()`. Only when the use count drops to zero
|
||||
will the DRM core disable the vertical blanking interrupts after a delay
|
||||
by scheduling a timer. The delay is accessible through the
|
||||
vblankoffdelay module parameter or the ``drm_vblank_offdelay`` global
|
||||
variable and expressed in milliseconds. Its default value is 5000 ms.
|
||||
Zero means never disable, and a negative value means disable
|
||||
immediately. Drivers may override the behaviour by setting the
|
||||
:c:type:`struct drm_device <drm_device>`
|
||||
vblank_disable_immediate flag, which when set causes vblank interrupts
|
||||
to be disabled immediately regardless of the drm_vblank_offdelay
|
||||
value. The flag should only be set if there's a properly working
|
||||
hardware vblank counter present.
|
||||
|
||||
When a vertical blanking interrupt occurs drivers only need to call the
|
||||
:c:func:`drm_handle_vblank()` function to account for the
|
||||
interrupt.
|
||||
|
||||
Resources allocated by :c:func:`drm_vblank_init()` must be freed
|
||||
with a call to :c:func:`drm_vblank_cleanup()` in the driver unload
|
||||
operation handler.
|
||||
.. kernel-doc:: drivers/gpu/drm/drm_vblank.c
|
||||
:doc: vblank handling
|
||||
|
||||
Vertical Blanking and Interrupt Handling Functions Reference
|
||||
------------------------------------------------------------
|
||||
|
||||
@ -31,6 +31,41 @@
|
||||
#include "drm_trace.h"
|
||||
#include "drm_internal.h"
|
||||
|
||||
/**
|
||||
* DOC: vblank handling
|
||||
*
|
||||
* Vertical blanking plays a major role in graphics rendering. To achieve
|
||||
* tear-free display, users must synchronize page flips and/or rendering to
|
||||
* vertical blanking. The DRM API offers ioctls to perform page flips
|
||||
* synchronized to vertical blanking and wait for vertical blanking.
|
||||
*
|
||||
* The DRM core handles most of the vertical blanking management logic, which
|
||||
* involves filtering out spurious interrupts, keeping race-free blanking
|
||||
* counters, coping with counter wrap-around and resets and keeping use counts.
|
||||
* It relies on the driver to generate vertical blanking interrupts and
|
||||
* optionally provide a hardware vertical blanking counter.
|
||||
*
|
||||
* Drivers must initialize the vertical blanking handling core with a call to
|
||||
* drm_vblank_init(). Minimally, a driver needs to implement
|
||||
* &drm_crtc_funcs.enable_vblank and &drm_crtc_funcs.disable_vblank plus call
|
||||
* drm_crtc_handle_vblank() in it's vblank interrupt handler for working vblank
|
||||
* support.
|
||||
*
|
||||
* Vertical blanking interrupts can be enabled by the DRM core or by drivers
|
||||
* themselves (for instance to handle page flipping operations). The DRM core
|
||||
* maintains a vertical blanking use count to ensure that the interrupts are not
|
||||
* disabled while a user still needs them. To increment the use count, drivers
|
||||
* call drm_crtc_vblank_get() and release the vblank reference again with
|
||||
* drm_crtc_vblank_put(). In between these two calls vblank interrupts are
|
||||
* guaranteed to be enabled.
|
||||
*
|
||||
* On many hardware disabling the vblank interrupt cannot be done in a race-free
|
||||
* manner, see &drm_driver.vblank_disable_immediate and
|
||||
* &drm_driver.max_vblank_count. In that case the vblank core only disables the
|
||||
* vblanks after a timer has expired, which can be configured through the
|
||||
* ``vblankoffdelay`` module parameter.
|
||||
*/
|
||||
|
||||
/* Retry timestamp calculation up to 3 times to satisfy
|
||||
* drm_timestamp_precision before giving up.
|
||||
*/
|
||||
@ -262,11 +297,12 @@ static u32 drm_vblank_count(struct drm_device *dev, unsigned int pipe)
|
||||
* drm_accurate_vblank_count - retrieve the master vblank counter
|
||||
* @crtc: which counter to retrieve
|
||||
*
|
||||
* This function is similar to @drm_crtc_vblank_count but this
|
||||
* function interpolates to handle a race with vblank irq's.
|
||||
* This function is similar to drm_crtc_vblank_count() but this function
|
||||
* interpolates to handle a race with vblank interrupts using the high precision
|
||||
* timestamping support.
|
||||
*
|
||||
* This is mostly useful for hardware that can obtain the scanout
|
||||
* position, but doesn't have a frame counter.
|
||||
* This is mostly useful for hardware that can obtain the scanout position, but
|
||||
* doesn't have a hardware frame counter.
|
||||
*/
|
||||
u32 drm_accurate_vblank_count(struct drm_crtc *crtc)
|
||||
{
|
||||
@ -362,10 +398,14 @@ static void vblank_disable_fn(unsigned long arg)
|
||||
* drm_vblank_cleanup - cleanup vblank support
|
||||
* @dev: DRM device
|
||||
*
|
||||
* This function cleans up any resources allocated in drm_vblank_init.
|
||||
* This function cleans up any resources allocated in drm_vblank_init(). It is
|
||||
* called by the DRM core when @dev is finalized.
|
||||
*
|
||||
* Drivers can call drm_vblank_cleanup() if they need to quiescent the vblank
|
||||
* interrupt in their unload code. But in general this should be handled by
|
||||
* disabling all active &drm_crtc through e.g. drm_atomic_helper_shutdown, which
|
||||
* should end up calling drm_crtc_vblank_off().
|
||||
*
|
||||
* Drivers which don't use drm_irq_install() need to set &drm_device.irq_enabled
|
||||
* themselves, to signal to the DRM core that vblank interrupts are enabled.
|
||||
*/
|
||||
void drm_vblank_cleanup(struct drm_device *dev)
|
||||
{
|
||||
@ -396,6 +436,9 @@ EXPORT_SYMBOL(drm_vblank_cleanup);
|
||||
* @num_crtcs: number of CRTCs supported by @dev
|
||||
*
|
||||
* This function initializes vblank support for @num_crtcs display pipelines.
|
||||
* Drivers do not need to call drm_vblank_cleanup(), cleanup is already handled
|
||||
* by the DRM core, or through calling drm_dev_fini() for drivers with a
|
||||
* &drm_driver.release callback.
|
||||
*
|
||||
* Returns:
|
||||
* Zero on success or a negative error code on failure.
|
||||
@ -468,11 +511,11 @@ EXPORT_SYMBOL(drm_crtc_vblank_waitqueue);
|
||||
* @crtc: drm_crtc whose timestamp constants should be updated.
|
||||
* @mode: display mode containing the scanout timings
|
||||
*
|
||||
* Calculate and store various constants which are later
|
||||
* needed by vblank and swap-completion timestamping, e.g,
|
||||
* by drm_calc_vbltimestamp_from_scanoutpos(). They are
|
||||
* derived from CRTC's true scanout timing, so they take
|
||||
* things like panel scaling or other adjustments into account.
|
||||
* Calculate and store various constants which are later needed by vblank and
|
||||
* swap-completion timestamping, e.g, by
|
||||
* drm_calc_vbltimestamp_from_scanoutpos(). They are derived from CRTC's true
|
||||
* scanout timing, so they take things like panel scaling or other adjustments
|
||||
* into account.
|
||||
*/
|
||||
void drm_calc_timestamping_constants(struct drm_crtc *crtc,
|
||||
const struct drm_display_mode *mode)
|
||||
@ -535,25 +578,14 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants);
|
||||
* if flag is set.
|
||||
*
|
||||
* Implements calculation of exact vblank timestamps from given drm_display_mode
|
||||
* timings and current video scanout position of a CRTC. This can be called from
|
||||
* within get_vblank_timestamp() implementation of a kms driver to implement the
|
||||
* actual timestamping.
|
||||
* timings and current video scanout position of a CRTC. This can be directly
|
||||
* used as the &drm_driver.get_vblank_timestamp implementation of a kms driver
|
||||
* if &drm_driver.get_scanout_position is implemented.
|
||||
*
|
||||
* Should return timestamps conforming to the OML_sync_control OpenML
|
||||
* extension specification. The timestamp corresponds to the end of
|
||||
* the vblank interval, aka start of scanout of topmost-leftmost display
|
||||
* pixel in the following video frame.
|
||||
*
|
||||
* Requires support for optional dev->driver->get_scanout_position()
|
||||
* in kms driver, plus a bit of setup code to provide a drm_display_mode
|
||||
* that corresponds to the true scanout timing.
|
||||
*
|
||||
* The current implementation only handles standard video modes. It
|
||||
* returns as no operation if a doublescan or interlaced video mode is
|
||||
* active. Higher level code is expected to handle this.
|
||||
*
|
||||
* This function can be used to implement the &drm_driver.get_vblank_timestamp
|
||||
* directly, if the driver implements the &drm_driver.get_scanout_position hook.
|
||||
* The current implementation only handles standard video modes. For double scan
|
||||
* and interlaced modes the driver is supposed to adjust the hardware mode
|
||||
* (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
|
||||
* match the scanout position reported.
|
||||
*
|
||||
* Note that atomic drivers must call drm_calc_timestamping_constants() before
|
||||
* enabling a CRTC. The atomic helpers already take care of that in
|
||||
@ -738,7 +770,9 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
|
||||
*
|
||||
* Fetches the "cooked" vblank count value that represents the number of
|
||||
* vblank events since the system was booted, including lost events due to
|
||||
* modesetting activity.
|
||||
* modesetting activity. Note that this timer isn't correct against a racing
|
||||
* vblank interrupt (since it only reports the software vblank counter), see
|
||||
* drm_accurate_vblank_count() for such use-cases.
|
||||
*
|
||||
* Returns:
|
||||
* The software vblank counter.
|
||||
@ -749,20 +783,6 @@ u32 drm_crtc_vblank_count(struct drm_crtc *crtc)
|
||||
}
|
||||
EXPORT_SYMBOL(drm_crtc_vblank_count);
|
||||
|
||||
/**
|
||||
* drm_vblank_count_and_time - retrieve "cooked" vblank counter value and the
|
||||
* system timestamp corresponding to that vblank counter value.
|
||||
* @dev: DRM device
|
||||
* @pipe: index of CRTC whose counter to retrieve
|
||||
* @vblanktime: Pointer to struct timeval to receive the vblank timestamp.
|
||||
*
|
||||
* Fetches the "cooked" vblank count value that represents the number of
|
||||
* vblank events since the system was booted, including lost events due to
|
||||
* modesetting activity. Returns corresponding system timestamp of the time
|
||||
* of the vblank interval that corresponds to the current vblank counter value.
|
||||
*
|
||||
* This is the legacy version of drm_crtc_vblank_count_and_time().
|
||||
*/
|
||||
static u32 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe,
|
||||
struct timeval *vblanktime)
|
||||
{
|
||||
@ -852,8 +872,8 @@ static void send_vblank_event(struct drm_device *dev,
|
||||
* handler by calling drm_crtc_send_vblank_event() and make sure that there's no
|
||||
* possible race with the hardware committing the atomic update.
|
||||
*
|
||||
* Caller must hold event lock. Caller must also hold a vblank reference for
|
||||
* the event @e, which will be dropped when the next vblank arrives.
|
||||
* Caller must hold a vblank reference for the event @e, which will be dropped
|
||||
* when the next vblank arrives.
|
||||
*/
|
||||
void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
|
||||
struct drm_pending_vblank_event *e)
|
||||
@ -913,14 +933,6 @@ static int __enable_vblank(struct drm_device *dev, unsigned int pipe)
|
||||
return dev->driver->enable_vblank(dev, pipe);
|
||||
}
|
||||
|
||||
/**
|
||||
* drm_vblank_enable - enable the vblank interrupt on a CRTC
|
||||
* @dev: DRM device
|
||||
* @pipe: CRTC index
|
||||
*
|
||||
* Returns:
|
||||
* Zero on success or a negative error code on failure.
|
||||
*/
|
||||
static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
|
||||
{
|
||||
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
|
||||
@ -958,19 +970,6 @@ static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
|
||||
return ret;
|
||||
}
|
||||
|
||||
/**
|
||||
* drm_vblank_get - get a reference count on vblank events
|
||||
* @dev: DRM device
|
||||
* @pipe: index of CRTC to own
|
||||
*
|
||||
* Acquire a reference count on vblank events to avoid having them disabled
|
||||
* while in use.
|
||||
*
|
||||
* This is the legacy version of drm_crtc_vblank_get().
|
||||
*
|
||||
* Returns:
|
||||
* Zero on success or a negative error code on failure.
|
||||
*/
|
||||
static int drm_vblank_get(struct drm_device *dev, unsigned int pipe)
|
||||
{
|
||||
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
|
||||
@ -1014,16 +1013,6 @@ int drm_crtc_vblank_get(struct drm_crtc *crtc)
|
||||
}
|
||||
EXPORT_SYMBOL(drm_crtc_vblank_get);
|
||||
|
||||
/**
|
||||
* drm_vblank_put - release ownership of vblank events
|
||||
* @dev: DRM device
|
||||
* @pipe: index of CRTC to release
|
||||
*
|
||||
* Release ownership of a given vblank counter, turning off interrupts
|
||||
* if possible. Disable interrupts after drm_vblank_offdelay milliseconds.
|
||||
*
|
||||
* This is the legacy version of drm_crtc_vblank_put().
|
||||
*/
|
||||
static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
|
||||
{
|
||||
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
|
||||
@ -1067,6 +1056,8 @@ EXPORT_SYMBOL(drm_crtc_vblank_put);
|
||||
* This waits for one vblank to pass on @pipe, using the irq driver interfaces.
|
||||
* It is a failure to call this when the vblank irq for @pipe is disabled, e.g.
|
||||
* due to lack of driver support or because the crtc is off.
|
||||
*
|
||||
* This is the legacy version of drm_crtc_wait_one_vblank().
|
||||
*/
|
||||
void drm_wait_one_vblank(struct drm_device *dev, unsigned int pipe)
|
||||
{
|
||||
@ -1116,7 +1107,7 @@ EXPORT_SYMBOL(drm_crtc_wait_one_vblank);
|
||||
* stored so that drm_vblank_on can restore it again.
|
||||
*
|
||||
* Drivers must use this function when the hardware vblank counter can get
|
||||
* reset, e.g. when suspending.
|
||||
* reset, e.g. when suspending or disabling the @crtc in general.
|
||||
*/
|
||||
void drm_crtc_vblank_off(struct drm_crtc *crtc)
|
||||
{
|
||||
@ -1184,6 +1175,8 @@ EXPORT_SYMBOL(drm_crtc_vblank_off);
|
||||
* drm_crtc_vblank_on() functions. The difference compared to
|
||||
* drm_crtc_vblank_off() is that this function doesn't save the vblank counter
|
||||
* and hence doesn't need to call any driver hooks.
|
||||
*
|
||||
* This is useful for recovering driver state e.g. on driver load, or on resume.
|
||||
*/
|
||||
void drm_crtc_vblank_reset(struct drm_crtc *crtc)
|
||||
{
|
||||
@ -1212,9 +1205,10 @@ EXPORT_SYMBOL(drm_crtc_vblank_reset);
|
||||
* @crtc: CRTC in question
|
||||
*
|
||||
* This functions restores the vblank interrupt state captured with
|
||||
* drm_crtc_vblank_off() again. Note that calls to drm_crtc_vblank_on() and
|
||||
* drm_crtc_vblank_off() can be unbalanced and so can also be unconditionally called
|
||||
* in driver load code to reflect the current hardware state of the crtc.
|
||||
* drm_crtc_vblank_off() again and is generally called when enabling @crtc. Note
|
||||
* that calls to drm_crtc_vblank_on() and drm_crtc_vblank_off() can be
|
||||
* unbalanced and so can also be unconditionally called in driver load code to
|
||||
* reflect the current hardware state of the crtc.
|
||||
*/
|
||||
void drm_crtc_vblank_on(struct drm_crtc *crtc)
|
||||
{
|
||||
|
||||
@ -387,22 +387,49 @@ struct drm_device {
|
||||
bool irq_enabled;
|
||||
int irq;
|
||||
|
||||
/*
|
||||
/**
|
||||
* @vblank_disable_immediate:
|
||||
*
|
||||
* If true, vblank interrupt will be disabled immediately when the
|
||||
* refcount drops to zero, as opposed to via the vblank disable
|
||||
* timer.
|
||||
* This can be set to true it the hardware has a working vblank
|
||||
* counter and the driver uses drm_vblank_on() and drm_vblank_off()
|
||||
* appropriately.
|
||||
*
|
||||
* This can be set to true it the hardware has a working vblank counter
|
||||
* with high-precision timestamping (otherwise there are races) and the
|
||||
* driver uses drm_crtc_vblank_on() and drm_crtc_vblank_off()
|
||||
* appropriately. See also @max_vblank_count and
|
||||
* &drm_crtc_funcs.get_vblank_counter.
|
||||
*/
|
||||
bool vblank_disable_immediate;
|
||||
|
||||
/* array of size num_crtcs */
|
||||
/**
|
||||
* @vblank:
|
||||
*
|
||||
* Array of vblank tracking structures, one per &struct drm_crtc. For
|
||||
* historical reasons (vblank support predates kernel modesetting) this
|
||||
* is free-standing and not part of &struct drm_crtc itself. It must be
|
||||
* initialized explicitly by calling drm_vblank_init().
|
||||
*/
|
||||
struct drm_vblank_crtc *vblank;
|
||||
|
||||
spinlock_t vblank_time_lock; /**< Protects vblank count and time updates during vblank enable/disable */
|
||||
spinlock_t vbl_lock;
|
||||
|
||||
/**
|
||||
* @max_vblank_count:
|
||||
*
|
||||
* Maximum value of the vblank registers. This value +1 will result in a
|
||||
* wrap-around of the vblank register. It is used by the vblank core to
|
||||
* handle wrap-arounds.
|
||||
*
|
||||
* If set to zero the vblank core will try to guess the elapsed vblanks
|
||||
* between times when the vblank interrupt is disabled through
|
||||
* high-precision timestamps. That approach is suffering from small
|
||||
* races and imprecision over longer time periods, hence exposing a
|
||||
* hardware vblank counter is always recommended.
|
||||
*
|
||||
* If non-zeor, &drm_crtc_funcs.get_vblank_counter must be set.
|
||||
*/
|
||||
u32 max_vblank_count; /**< size of vblank counter register */
|
||||
|
||||
/**
|
||||
|
||||
@ -685,6 +685,9 @@ struct drm_crtc_funcs {
|
||||
* drm_crtc_vblank_off() and drm_crtc_vblank_on() when disabling or
|
||||
* enabling a CRTC.
|
||||
*
|
||||
* See also &drm_device.vblank_disable_immediate and
|
||||
* &drm_device.max_vblank_count.
|
||||
*
|
||||
* Returns:
|
||||
*
|
||||
* Raw vblank counter value.
|
||||
|
||||
Loading…
Reference in New Issue
Block a user