Hello,
this series first fixes the calculation of the clock rate. The driver will
round up to the nearest clock rate instead of rounding down. Resulting in SPI
devices accessed with a too high SPI clock.
The remaining patches improve the performance of the driver. The changes range
from micro-optimizations like reducing MMIO writes to the controller to
reducing the number of needed interrupts in some use cases.
regards,
Marc
changes since v1:
- added Maxime Ripard's to the existing patches
- 06/10: (was 05/10 in v1)
"spi: spi-sun6i: sun6i_spi_drain_fifo(): introduce sun6i_spi_get_rx_fifo_count() and make use of it"
use FIELD_GET instead of open coding it
(tnx: Maxime Ripard)
- 05/10: "spi: spi-sun6i: sun6i_spi_get_tx_fifo_count: Convert manual shift+mask to FIELD_GET()"
new patch
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.orghttp://lists.infradead.org/mailman/listinfo/linux-arm-kernel
The PXA2xx SPI driver releases a runtime PM ref in the probe error path
even though it hasn't acquired a ref earlier.
Apparently commit e2b714afee ("spi: pxa2xx: Disable runtime PM if
controller registration fails") sought to copy-paste the invocation of
pm_runtime_disable() from pxa2xx_spi_remove(), but erroneously copied
the call to pm_runtime_put_noidle() as well. Drop it.
Fixes: e2b714afee ("spi: pxa2xx: Disable runtime PM if controller registration fails")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: stable@vger.kernel.org # v4.17+
Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/58b2ac6942ca1f91aaeeafe512144bc5343e1d84.1590408496.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
The PXA2xx SPI driver uses devm_spi_register_controller() on bind.
As a consequence, on unbind, __device_release_driver() first invokes
pxa2xx_spi_remove() before unregistering the SPI controller via
devres_release_all().
This order is incorrect: pxa2xx_spi_remove() disables the chip,
rendering the SPI bus inaccessible even though the SPI controller is
still registered. When the SPI controller is subsequently unregistered,
it unbinds all its slave devices. Because their drivers cannot access
the SPI bus, e.g. to quiesce interrupts, the slave devices may be left
in an improper state.
As a rule, devm_spi_register_controller() must not be used if the
->remove() hook performs teardown steps which shall be performed after
unregistering the controller and specifically after unbinding of slaves.
Fix by reverting to the non-devm variant of spi_register_controller().
An alternative approach would be to use device-managed functions for all
steps in pxa2xx_spi_remove(), e.g. by calling devm_add_action_or_reset()
on probe. However that approach would add more LoC to the driver and
it wouldn't lend itself as well to backporting to stable.
The improper use of devm_spi_register_controller() was introduced in 2013
by commit a807fcd090 ("spi: pxa2xx: use devm_spi_register_master()"),
but all earlier versions of the driver going back to 2006 were likewise
broken because they invoked spi_unregister_master() at the end of
pxa2xx_spi_remove(), rather than at the beginning.
Fixes: e0c9905e87 ("[PATCH] SPI: add PXA2xx SSP SPI Driver")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: stable@vger.kernel.org # v2.6.17+
Cc: Tsuchiya Yuto <kitakar@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206403#c1
Link: https://lore.kernel.org/r/834c446b1cf3284d2660f1bee1ebe3e737cd02a9.1590408496.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
With a couple allies at Intel, and much badgering, I got confirmation
from Intel that at least BXT suffers from the same SPI chip-select
issue as Cannonlake (and beyond). The issue being that after going
through runtime suspend/resume, toggling the chip-select line without
also sending data does nothing.
Add the quirk to BXT to briefly toggle dynamic clock gating off and
on, forcing the fabric to wake up enough to notice the CS register
change.
Signed-off-by: Evan Green <evgreen@chromium.org>
Cc: Shobhit Srivastava <shobhit.srivastava@intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200427163238.1.Ib1faaabe236e37ea73be9b8dcc6aa034cb3c8804@changeid
Signed-off-by: Mark Brown <broonie@kernel.org>
In some circumstances on Intel LPSS controllers, toggling the LPSS
CS control register doesn't actually cause the CS line to toggle.
This seems to be failure of dynamic clock gating that occurs after
going through a suspend/resume transition, where the controller
is sent through a reset transition. This ruins SPI transactions
that either rely on delay_usecs, or toggle the CS line without
sending data.
Whenever CS is toggled, momentarily set the clock gating register
to "Force On" to poke the controller into acting on CS.
Signed-off-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Evan Green <evgreen@chromium.org>
Link: https://lore.kernel.org/r/20200211223700.110252-1-rajatja@google.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Add support for Intel Comet Lake PCH-V which has the same LPSS than on
Intel Kaby lake unlike other Intel Comet Lake PCH variants that are based
on Intel Cannon Lake PCH LPSS.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20200116091035.575175-1-jarkko.nikula@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
A relatively large set of fixes here, the biggest part of it is for
fallout from the GPIO descriptor rework that affected several of the
devices with usable native chip select support. There's also some new
PCI IDs for Intel Jasper Lake devices.
The conversion to platform_get_irq() in the fsl driver is an incremental
fix for build errors introduced on SPARC by the earlier fix for error
handling in probe in that driver.
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Merge tag 'spi-fix-v5.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi
Pull spi fixes from Mark Brown:
"A relatively large set of fixes here, the biggest part of it is for
fallout from the GPIO descriptor rework that affected several of the
devices with usable native chip select support. There's also some new
PCI IDs for Intel Jasper Lake devices.
The conversion to platform_get_irq() in the fsl driver is an
incremental fix for build errors introduced on SPARC by the earlier
fix for error handling in probe in that driver"
* tag 'spi-fix-v5.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi:
spi: fsl: use platform_get_irq() instead of of_irq_to_resource()
spi: nxp-fspi: Ensure width is respected in spi-mem operations
spi: spi-ti-qspi: Fix a bug when accessing non default CS
spi: fsl: don't map irq during probe
spi: spi-cavium-thunderx: Add missing pci_release_regions()
spi: sprd: Fix the incorrect SPI register
gpiolib: of: Make of_gpio_spi_cs_get_count static
spi: fsl: Handle the single hardwired chipselect case
gpio: Handle counting of Freescale chipselects
spi: fsl: Fix GPIO descriptor support
spi: dw: Correct handling of native chipselect
spi: cadence: Correct handling of native chipselect
spi: pxa2xx: Add support for Intel Jasper Lake
LPSS SPI on Intel Jasper Lake is compatible with Intel Ice Lake which
follows Intel Cannon Lake. Add PCI IDs of Jasper Lake.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20191125125159.15404-1-jarkko.nikula@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
pxa2xx_spi_init_pdata misses checks for devm_clk_get and
platform_get_irq.
Add checks for them to fix the bugs.
Since ssp->clk and ssp->irq are used in probe, they are mandatory here.
So we cannot use _optional() for devm_clk_get and platform_get_irq.
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Link: https://lore.kernel.org/r/20191109080943.30428-1-hslester96@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
The current conditional for PCI ID matching is hard to read.
Introduce couple of temporary variables to increase readability
of the code.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20191021103625.4250-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
The devm_ioremap_resource() has already a check for resource pointer
being NULL. No need to double check this.
Drop extra check of platform_get_resource() returned value.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20191021103625.4250-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Convert to use device_get_match_data() instead of open coded variant.
While here, switch of_property_read_bool() to device_property_read_bool().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20191018105429.82782-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
There is no need to keep a pointer to the platform device. Currently there are
no users of it directly, and if there will be in the future we may restore it
from pointer to the struct device.
Convert all users at the same time.
Cc: Russell King <linux@armlinux.org.uk>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20191018105429.82782-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
In DMA mode we have a maximum transfer size, past that the driver
falls back to PIO (see the check at the top of pxa2xx_spi_transfer_one).
Falling back to PIO for big transfers defeats the point of a dma engine,
hence set the max transfer size to inform spi clients that they need
to do something smarter.
This was uncovered by the drm_mipi_dbi spi panel code, which does
large spi transfers, but stopped splitting them after:
commit e143364b4c
Author: Noralf Trønnes <noralf@tronnes.org>
Date: Fri Jul 19 17:59:10 2019 +0200
drm/tinydrm: Remove tinydrm_spi_max_transfer_size()
After this commit the code relied on the spi core to split transfers
into max dma-able blocks, which also papered over the PIO fallback issue.
Fix this by setting the overall max transfer size to the DMA limit,
but only when the controller runs in DMA mode.
Fixes: e143364b4c ("drm/tinydrm: Remove tinydrm_spi_max_transfer_size()")
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Reported-and-tested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: Mark Brown <broonie@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-spi@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://lore.kernel.org/r/20191017064426.30814-1-daniel.vetter@ffwll.ch
Signed-off-by: Mark Brown <broonie@kernel.org>
Intel Tiger Lake -LP LPSS SPI controller is otherwise similar than
Cannon Lake but has more controllers and up to two chip selects per
controller.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20190801134901.12635-1-jarkko.nikula@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Don't undo the PM initialization if we error out before we managed to
initialize it. The call to pm_runtime_disable() without being preceded
by pm_runtime_enable() would disturb the balance of the Force.
In practice, this happens if we fail to allocate any of the GPIOS ("cs",
"ready") due to -EPROBE_DEFER because we're getting probled before the
GPIO driver.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lore.kernel.org/r/20190719122713.3444318-1-lkundrak@v3.sk
Signed-off-by: Mark Brown <broonie@kernel.org>
It is possible to request a transfer with a speed lower than supported
by the HW. This causes silent divider calculation underflow in
ssp_get_clk_div() which leads to a frequency higher than requested. Up to
maximum speed of the controller.
Set the minimum supported transfer speed and let the SPI core to
validate no transfers have speed lower than supported.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Based on 3 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [kishon] [vijay] [abraham]
[i] [kishon]@[ti] [com] this program is distributed in the hope that
it will be useful but without any warranty without even the implied
warranty of merchantability or fitness for a particular purpose see
the gnu general public license for more details
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [graeme] [gregory]
[gg]@[slimlogic] [co] [uk] [author] [kishon] [vijay] [abraham] [i]
[kishon]@[ti] [com] [based] [on] [twl6030]_[usb] [c] [author] [hema]
[hk] [hemahk]@[ti] [com] this program is distributed in the hope
that it will be useful but without any warranty without even the
implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1105 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.202006027@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
- Updates to stm32 dma residue calculations
- Interleave dma capability to axi-dmac and
support for ZynqMP arch
- Rework of channel assignment for rcar dma
- Debugfs for pl330 driver
- Support for Tegra186/Tegra194, refactoring for new chips
and support for pause/resume
- Updates to axi-dmac, bcm2835, fsl-edma, idma64, imx-sdma,
rcar-dmac, stm32-dma etc
- dev_get_drvdata() updates on few drivers
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Merge tag 'dmaengine-5.2-rc1' of git://git.infradead.org/users/vkoul/slave-dma
Pull dmaengine updates from Vinod Koul:
- Updates to stm32 dma residue calculations
- Interleave dma capability to axi-dmac and support for ZynqMP arch
- Rework of channel assignment for rcar dma
- Debugfs for pl330 driver
- Support for Tegra186/Tegra194, refactoring for new chips and support
for pause/resume
- Updates to axi-dmac, bcm2835, fsl-edma, idma64, imx-sdma, rcar-dmac,
stm32-dma etc
- dev_get_drvdata() updates on few drivers
* tag 'dmaengine-5.2-rc1' of git://git.infradead.org/users/vkoul/slave-dma: (34 commits)
dmaengine: tegra210-adma: restore channel status
dmaengine: tegra210-dma: free dma controller in remove()
dmaengine: tegra210-adma: add pause/resume support
dmaengine: tegra210-adma: add support for Tegra186/Tegra194
Documentation: DT: Add compatibility binding for Tegra186
dmaengine: tegra210-adma: prepare for supporting newer Tegra chips
dmaengine: at_xdmac: remove a stray bottom half unlock
dmaengine: fsl-edma: Adjust indentation
dmaengine: fsl-edma: Fix typo in Vybrid name
dmaengine: stm32-dma: fix residue calculation in stm32-dma
dmaengine: nbpfaxi: Use dev_get_drvdata()
dmaengine: bcm-sba-raid: Use dev_get_drvdata()
dmaengine: stm32-dma: Fix unsigned variable compared with zero
dmaengine: stm32-dma: use platform_get_irq()
dmaengine: rcar-dmac: Update copyright information
dmaengine: imx-sdma: Only check ratio on parts that support 1:1
dmaengine: xgene-dma: fix spelling mistake "descripto" -> "descriptor"
dmaengine: idma64: Move driver name to the header
dmaengine: bcm2835: Drop duplicate capability setting.
dmaengine: pl330: _stop: clear interrupt status
...
Calculate the divisor for the SCR (Serial Clock Rate), avoiding
that the SSP transmission rate can be greater than the device rate.
When the division between the SSP clock and the device rate generates
a reminder, we have to increment by one the divisor.
In this way the resulting SSP clock will never be greater than the
device SPI max frequency.
For example, with:
- ssp_clk = 50 MHz
- dev freq = 15 MHz
without this patch the SSP clock will be greater than 15 MHz:
- 25 MHz for PXA25x_SSP and CE4100_SSP
- 16,56 MHz for the others
Instead, with this patch, we have in both case an SSP clock of 12.5MHz,
so the max rate of the SPI device clock is respected.
Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Add PCI IDs for SPI on Comet Lake.
Signed-off-by: Evan Green <evgreen@chromium.org>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
With dw_dmac, sometimes the request of a DMA channel fails because
the DMA driver is not ready, so an explicit dependency request
is necessary.
Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Signed-off-by: Mark Brown <broonie@kernel.org>
Change the type of the diagnostic message:
"no DMA channels available, using PIO"
from debug to warning.
The lack of an available DMA channel is very important regard the
spi-pxa2xx performance. The transfer speed can be reduced more than 50%.
So it is very important to warn the user about this, without enabling
the full SPI debug with CONFIG_SPI_DEBUG.
Moreover, enabling the full SPI debug only to enable this specific
debug message, the dmesg buffer fills quickly with a lot of
repetitive information during the SPI data transfer.
This cause the loss of all the first important messages
written during the initialization.
Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Signed-off-by: Mark Brown <broonie@kernel.org>
Use SPI device pointer in the remaining two error and warning prints in
pxa2xx_spi_transfer_one() instead of platform device of the controller
It make prints in the function uniform and more useful especially the
error print here as it can reveal the driver that has mapped the DMA
itself and attempts to transfer more than the maximum supported DMA
transfer length.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Pointer to a SPI device is passed to pxa2xx_spi_transfer_one() so there
is no need to access it through the current SPI message pointer.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Intel IOMMU, when enabled, tries to find the domain of the device,
assuming it's a PCI one, during DMA operations, such as mapping or
unmapping. Since we are splitting the actual PCI device to couple of
children via MFD framework (see drivers/mfd/intel-lpss.c for details),
the DMA device appears to be a platform one, and thus not an actual one
that performs DMA. In a such situation IOMMU can't find or allocate
a proper domain for its operations. As a result, all DMA operations are
failed.
In order to fix this, supply parent of the platform device
to the DMA engine framework and fix filter functions accordingly.
We may rely on the fact that parent is a real PCI device, because no
other configuration is present in the wild.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [for tty parts]
Signed-off-by: Vinod Koul <vkoul@kernel.org>
It's useful during debug to see what DMA burst size is.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Some masters may have different DMA burst size than hard coded default.
In such case respect the value given by DMA burst size provided via
platform data.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
When the commit b6ced294fb
("spi: pxa2xx: Switch to SPI core DMA mapping functionality")
switches to SPI core provided DMA helpers, it missed to setup maximum
supported DMA transfer length for the controller and thus users
mistakenly try to send more data than supported with the following
warning:
ili9341 spi-PRP0001:01: DMA disabled for transfer length 153600 greater than 65536
Setup maximum supported DMA transfer length in order to make users know
the limit.
Fixes: b6ced294fb ("spi: pxa2xx: Switch to SPI core DMA mapping functionality")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
It's also a slave controller driver now, calling it "master" is slightly
misleading.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>
There doesn't seem to be a way to empty TXFIFO on MMP2. The datasheet is
super-secret and the method described in Armada 16x manual won't work:
"The TXFIFO and RXFIFO are cleared to 0b0 when the SSPx port is reset or
disabled (by writing a 0b0 to the <Synchronous Serial Port Enable> field
in the SSP Control Register 0)."
# devmem 0xd4037008 # read SSSR
0x0000F204
# devmem 0xd4037000 32 0x07 # SSE off in SSCR0
# devmem 0xd4037000 32 0x87 # SSE on
# devmem 0xd4037008
0x0000F204
^ TXFIFO level is still 2. Sigh.
The OLPC 1.75 boot firmware leaves two bytes in the TXFIFO. Those are
basically throwaway bytes used in response to the messages from the EC.
The OLPC kernel copes with this by power-cycling the hardware. Perhaps
the firmware should do this instead.
Other than that, there's not much we can do other than complain loudly
until the garbage gets drained and discard the actual data... For the
OLPC EC this will work just fine and pushing more data to TXFIFO would
break further transactions.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Mark Brown <broonie@kernel.org>
Strobe a GPIO line when the slave TX FIFO is filled. This is how the
Embedded Controller on an OLPC XO-1.75 machine, that happens to be a SPI
master, learns that it can initiate a transaction.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Tested-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>
