Status of ADMA channel registers is not saved and restored during system
suspend. During active playback if system enters suspend, this results in
wrong state of channel registers during system resume and playback fails
to resume properly. Fix this by saving following channel registers in
runtime suspend and restore during runtime resume.
 * ADMA_CH_LOWER_SRC_ADDR
 * ADMA_CH_LOWER_TRG_ADDR
 * ADMA_CH_FIFO_CTRL
 * ADMA_CH_CONFIG
 * ADMA_CH_CTRL
 * ADMA_CH_CMD
 * ADMA_CH_TC
Runtime PM calls will be inovked during system resume path if a playback
or capture needs to be resumed. Hence above changes work fine for system
suspend case.

Fixes: f46b1957 ("dmaengine: tegra-adma: Add support for Tegra210 ADMA")
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Following kernel panic is seen during DMA driver unload->load sequence
==========================================================================
Unable to handle kernel paging request at virtual address ffffff8001198880
Internal error: Oops: 86000007 [#1] PREEMPT SMP
CPU: 0 PID: 5907 Comm: HwBinder:4123_1 Tainted: G C 4.9.128-tegra-g065839f
Hardware name: galen (DT)
task: ffffffc3590d1a80 task.stack: ffffffc3d0678000
PC is at 0xffffff8001198880
LR is at of_dma_request_slave_channel+0xd8/0x1f8
pc : [<ffffff8001198880>] lr : [<ffffff8008746f30>] pstate: 60400045
sp : ffffffc3d067b710
x29: ffffffc3d067b710 x28: 000000000000002f
x27: ffffff800949e000 x26: ffffff800949e750
x25: ffffff800949e000 x24: ffffffbefe817d84
x23: ffffff8009f77cb0 x22: 0000000000000028
x21: ffffffc3ffda49c8 x20: 0000000000000029
x19: 0000000000000001 x18: ffffffffffffffff
x17: 0000000000000000 x16: ffffff80082b66a0
x15: ffffff8009e78250 x14: 000000000000000a
x13: 0000000000000038 x12: 0101010101010101
x11: 0000000000000030 x10: 0101010101010101
x9 : fffffffffffffffc x8 : 7f7f7f7f7f7f7f7f
x7 : 62ff726b6b64622c x6 : 0000000000008064
x5 : 6400000000000000 x4 : ffffffbefe817c44
x3 : ffffffc3ffda3e08 x2 : ffffff8001198880
x1 : ffffffc3d48323c0 x0 : ffffffc3d067b788

Process HwBinder:4123_1 (pid: 5907, stack limit = 0xffffffc3d0678028)
Call trace:
[<ffffff8001198880>] 0xffffff8001198880
[<ffffff80087459f8>] dma_request_chan+0x50/0x1f0
[<ffffff8008745bc0>] dma_request_slave_channel+0x28/0x40
[<ffffff8001552c44>] tegra_alt_pcm_open+0x114/0x170
[<ffffff8008d65fa4>] soc_pcm_open+0x10c/0x878
[<ffffff8008d18618>] snd_pcm_open_substream+0xc0/0x170
[<ffffff8008d1878c>] snd_pcm_open+0xc4/0x240
[<ffffff8008d189e0>] snd_pcm_playback_open+0x58/0x80
[<ffffff8008cfc6d4>] snd_open+0xb4/0x178
[<ffffff8008250628>] chrdev_open+0xb8/0x1d0
[<ffffff8008246fdc>] do_dentry_open+0x214/0x318
[<ffffff80082485d0>] vfs_open+0x58/0x88
[<ffffff800825bce0>] do_last+0x450/0xde0
[<ffffff800825c718>] path_openat+0xa8/0x368
[<ffffff800825dd84>] do_filp_open+0x8c/0x110
[<ffffff8008248a74>] do_sys_open+0x164/0x220
[<ffffff80082b66dc>] compat_SyS_openat+0x3c/0x50
[<ffffff8008083040>] el0_svc_naked+0x34/0x38
---[ end trace 67e6d544e65b5145 ]---
Kernel panic - not syncing: Fatal exception
==========================================================================

In device probe(), of_dma_controller_register() registers DMA controller.
But when driver is removed, this is not freed. During driver reload this
results in data abort and kernel panic. Add of_dma_controller_free() in
driver remove path to fix the issue.

Fixes: f46b1957 ("dmaengine: tegra-adma: Add support for Tegra210 ADMA")
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

During an audio playback session it is observed that, audio goes off after
few seconds of continuous pause and play. No audio is heard even when the
playback is resumed.

The reason for above is, currently ADMA driver does not handle DMA_PAUSE/
DMA_RESUME and relevant callbacks for dma_device are not implemented. This
patch implements device_pause and device_resume callbacks for the device.
During pause TRANSFER_PAUSE bit of dma channel control register is set and
the same is cleared during resume.
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Add Tegra186 specific macro defines and chip_data structure for chip
specific information. New compatibility is added to select relevant
chip details. There is no major change for Tegra194 and hence it can
use the same chip data.

The bits in the BURST_SIZE field of the ADMA CH_CONFIG register are
encoded differently on Tegra186 and Tegra194 compared with Tegra210.
On Tegra210 the bits are encoded as follows ...

 1 = WORD_1
 2 = WORDS_2
 3 = WORDS_4
 4 = WORDS_8
 5 = WORDS_16

Where as on Tegra186 and Tegra194 the bits are encoded as ...

 0 = WORD_1
 1 = WORDS_2
 2 = WORDS_3
 3 = WORDS_4
 4 = WORDS_5
 ...
 15 = WORDS_16

Add helper functions for generating the correct burst size.
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Tegra186 Audio DMA controller has new updates from Tegra210 version.
Thus add new compatibility binding string and the same can be used
by Tegra194 as well.
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

This is a preparatory patch to add support for Tegra186 and Tegra194 chips.
Following changes are necessary to make driver code generic.
 * chip_data structure is enhanced to have chip specific details and
   following are the additions to the structure
   * Offset addresses for ADMA global and channel registers
   * Offset values for Tx and Rx channel selection
   * Maximum supported Tx and Rx channels
   * Tx and Rx channel request mask
   * ADMA channel register space size
 * Make use of above chip_data to generalise the driver code

Support for Tegra186 and Tegra194 will be added in subsequent patches of
the series.
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

We switched this code from spin_lock_bh() to vanilla spin_lock() but
there was one stray spin_unlock_bh() that was overlooked.  This
patch converts it to spin_unlock() as well.

Fixes: d8570d01 ("dmaengine: at_xdmac: move spin_lock_bh to spin_lock in tasklet")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Fix indentation and remove unneeded space after 'return' keyword.  This
fixes checkpatch warning:
    WARNING: Statements should start on a tabstop
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Fix typo in comment for Vybrid SoC family.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

In double buffer mode, during residue calculation, the DMA can
automatically switch to the next transfer. Indeed the CT bit that
gives position in the double buffer can has been updated by the
hardware, during calculation.
In this case the SxNDTR register value can not be trusted.
If a transition is detected we consider that the DMA has switched to
the beginning of next sg.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Using dev_get_drvdata directly.

Cc: Vinod Koul <vinod.koul@intel.com>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Using dev_get_drvdata directly.

Cc: Vinod Koul <vinod.koul@intel.com>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Commit f4fd2ec0: ("dmaengine: stm32-dma: use platform_get_irq()") used
unsigned variable irq to store the results and check later for negative
errors, so update the code to use signed variable for this

Fixes: f4fd2ec0 ("dmaengine: stm32-dma: use platform_get_irq()")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

platform_get_resource(pdev, IORESOURCE_IRQ) is not recommended for
requesting IRQ's resources, as they can be not ready yet. Using
platform_get_irq() instead is preferred for getting IRQ even if it was
not retrieved earlier.
Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Update copyright and string for Gen3.
Signed-off-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

On imx8mq B0 chip, AHB/SDMA clock ratio 2:1 can't be supported,
since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
to 500Mhz, so use 1:1 instead.

To limit this change to the imx8mq for now this patch also adds an
im8mq-sdma compatible string.
Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
Acked-by: Robin Gong <yibin.gong@nxp.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

There is a spelling mistake in a chan_dbg message, fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

There are two drivers that are relying on the iDMA 64-bit driver name
to match. Instead of duplicating string in both of them, dedicate
a header file and share it between users.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

This patch kill instructs the DMAC to immediately terminate
execution of a thread. and then clear the interrupt status,
at last, stop generating interrupts for DMA_SEV. to guarantee
the next dma start is clean. otherwise, one interrupt maybe leave
to next start and make some mistake.

we can reporduce the problem as follows:

DMASEV: modify the event-interrupt resource, and if the INTEN sets
function as interrupt, the DMAC will set irq<event_num> HIGH to
generate interrupt. write INTCLR to clear interrupt.

	DMA EXECUTING INSTRUCTS		DMA TERMINATE
		|				|
		|				|
	       ...			      _stop
		|				|
		|			spin_lock_irqsave
	     DMASEV				|
		|				|
		|			    mask INTEN
		|				|
		|			     DMAKILL
		|				|
		|			spin_unlock_irqrestore

in above case, a interrupt was left, and if we unmask INTEN, the DMAC
will set irq<event_num> HIGH to generate interrupt.

to fix this, do as follows:

	DMA EXECUTING INSTRUCTS		DMA TERMINATE
		|				|
		|				|
	       ...			      _stop
		|				|
		|			spin_lock_irqsave
	     DMASEV				|
		|				|
		|			     DMAKILL
		|				|
		|			   clear INTCLR
		|			    mask INTEN
		|				|
		|			spin_unlock_irqrestore
Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Since device_prep_interleaved_dma() is already implemented, the
DMA_INTERLEAVE capability should be set.
Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

In 2D transfers (for the AXI DMAC), the number of frames (numf) represents
Y_LENGTH, and the length of a frame is X_LENGTH. 2D transfers are useful
for video transfers where screen resolutions ( X * Y ) are typically
aligned for X, but not for Y.

There is no requirement for Y_LENGTH to be aligned to the bus-width (or
anything), and this is also true for AXI DMAC.

Checking the Y_LENGTH for alignment causes false errors when initiating DMA
transfers. This change fixes this by checking only that the Y_LENGTH is
non-zero.

Fixes: 0e3b67b3 ("dmaengine: Add support for the Analog Devices AXI-DMAC DMA controller")
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Some synthesis time configuration parameters of the DMA controller can be
inferred from the hardware itself.

Use this information as it is more reliably than the information specified
in the devicetree which might be outdated if the HDL project got changed.

Deprecate the devicetree properties that can be inferred from the hardware
itself.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

The overflow error flag (ROI: Request Overflow Error) is only relevant
for the case when the channel handles a peripheral synchronized transfer.
Not in the case of memory to memory transfer where there is no hardware
request signal.

Remove the use of this interrupt source in such a case. It's based on
the first descriptor which holds the configuration for the whole
linked list transfer.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Complement the identification of errors with stopping the channel and
dumping the descriptor that led to the error case.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Even if this case shouldn't happen when controller is properly programmed,
it's still better to avoid dumping a kernel Oops for this.
As the sequence may happen only for debugging purposes, log the error and
just finish the tasklet call.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

The AXI DMAC driver is currently supported also on the Xilinx ZynqMP
architecture. This change allows this driver to be enabled & used on it as
well.
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

It is unnecessary to call spin_lock_bh in a tasklet.
Signed-off-by: Jeff Xie <chongguiguzi@gmail.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Current way we find a waiting virtual channel for the next transfer
at the time one physical channel becomes free is not really fair.

More in details, in case there is more than one channel waiting at a time,
by just going through the arrays of memcpy and slave channels and stopping
as soon as state match waiting state, channels with high indexes can be
penalized.

Whenever dma engine is substantially overloaded so that we constantly
get several channels waiting, channels with highest indexes might not
be served for a substantial time which in the worse case, might hang
task that wait for dma transfer to complete.

This patch makes physical channel re-assignment more fair by storing
time in jiffies when a channel is put in waiting state. Whenever a
physical channel has to be re-assigned, this time is used to select
channel that is waiting for the longest time.
Signed-off-by: Jean-Nicolas Graux <jean-nicolas.graux@st.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Nicolas Guion <nicolas.guion@st.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

The axi-dmac driver currently rejects transfers with segments that are
larger than what the hardware can handle.

Re-work the driver so that these large segments are split into multiple
segments instead where each segment is smaller or equal to the maximum
segment size.

This allows the driver to handle transfers with segments of arbitrary size.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Bogdan Togorean <bogdan.togorean@analog.com>
Signed-off-by: Alexandru Ardelean <alex.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

This patch adds debugfs interface to show the relationship between
DMA threads (hardware resource for transferring data) and DMA
channel ID of DMA slave.

Typically, PL330 has many slaves than number of DMA threads.
So sometimes PL330 cannot allocate DMA threads for all slaves even
if a user specify DMA channel ID in devicetree. This interface will
be useful for checking that DMA threads are allocated or not.

Below is an output sample:

$ sudo cat /sys/kernel/debug/ff1f0000.dmac
PL330 physical channels:
THREAD:         CHANNEL:
--------        -----
0               8
1               9
2               11
3               12
4               14
5               15
6               10
7               --
Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

If the driver is active till late suspend, where runtime PM cannot run,
force suspend is essential in such case to put the device in low power
state. Thus pm_runtime_force_suspend and pm_runtime_force_resume are
used as system sleep callbacks during system wide PM transitions.
Late system sleep callbacks are used to ensure, for instance, that the
sound core has suspended any on-going activity, including stopping the
ADMA if active, before we attempt to suspend the ADMA.
Suggested-by: Jonathan Hunter <jonathanh@nvidia.com>
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

adma driver is using pm_clk_*() interface for managing clock resources.
With this it is observed that clocks remain ON always. This happens on
Tegra devices which use BPMP co-processor to manage clock resources,
where clocks are enabled during prepare phase. This is necessary because
clocks to BPMP are always blocking. When pm_clk_*() interface is used on
such Tegra devices, clock prepare count is not balanced till remove call
happens for the driver and hence clocks are seen ON always. Thus this
patch replaces pm_clk_*() with devm_clk_*() framework.
Suggested-by: Mohan Kumar D <mkumard@nvidia.com>
Reviewed-by: Jonathan Hunter <jonathanh@nvidia.com>
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@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>

Pull more Kbuild updates from Masahiro Yamada:

 - add more Build-Depends to Debian source package

 - prefix header search paths with $(srctree)/

 - make modpost show verbose section mismatch warnings

 - avoid hard-coded CROSS_COMPILE for h8300

 - fix regression for Debian make-kpkg command

 - add semantic patch to detect missing put_device()

 - fix some warnings of 'make deb-pkg'

 - optimize NOSTDINC_FLAGS evaluation

 - add warnings about redundant generic-y

 - clean up Makefiles and scripts

* tag 'kbuild-v5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: remove stale lxdialog/.gitignore
  kbuild: force all architectures except um to include mandatory-y
  kbuild: warn redundant generic-y
  Revert "modsign: Abort modules_install when signing fails"
  kbuild: Make NOSTDINC_FLAGS a simply expanded variable
  kbuild: deb-pkg: avoid implicit effects
  coccinelle: semantic code search for missing put_device()
  kbuild: pkg: grep include/config/auto.conf instead of $KCONFIG_CONFIG
  kbuild: deb-pkg: introduce is_enabled and if_enabled_echo to builddeb
  kbuild: deb-pkg: add CONFIG_ prefix to kernel config options
  kbuild: add workaround for Debian make-kpkg
  kbuild: source include/config/auto.conf instead of ${KCONFIG_CONFIG}
  unicore32: simplify linker script generation for decompressor
  h8300: use cc-cross-prefix instead of hardcoding h8300-unknown-linux-
  kbuild: move archive command to scripts/Makefile.lib
  modpost: always show verbose warning for section mismatch
  ia64: prefix header search path with $(srctree)/
  libfdt: prefix header search paths with $(srctree)/
  deb-pkg: generate correct build dependencies

Pull x86 asm updates from Thomas Gleixner:
 "Two cleanup patches removing dead conditionals and unused code"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm: Remove unused __constant_c_x_memset() macro and inlines
  x86/asm: Remove dead __GNUC__ conditionals

Pull perf fixes from Thomas Gleixner:
 "Three fixes for the fallout from the TSX errata workaround:

   - Prevent memory corruption caused by a unchecked out of bound array
     index.

   - Two trivial fixes to address compiler warnings"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel: Make dev_attr_allow_tsx_force_abort static
  perf/x86: Fixup typo in stub functions
  perf/x86/intel: Fix memory corruption

Pull xen fix from Juergen Gross:
 "A fix for a Xen bug introduced by David's series for excluding
  ballooned pages in vmcores"

* tag 'for-linus-5.1b-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/balloon: Fix mapping PG_offline pages to user space

Pull 9p updates from Dominique Martinet:
 "Here is a 9p update for 5.1; there honestly hasn't been much.

  Two fixes (leak on invalid mount argument and possible deadlock on
  i_size update on 32bit smp) and a fall-through warning cleanup"

* tag '9p-for-5.1' of git://github.com/martinetd/linux:
  9p/net: fix memory leak in p9_client_create
  9p: use inode->i_lock to protect i_size_write() under 32-bit
  9p: mark expected switch fall-through