During runtime PM we'll be reinitializing interrupt support from the
ground up. However since the display power well will be off at that
time, well end up with a ton of unclaimed register accesses from the
display irq setup. Since we turned off the power well already before
runtime suspend, we've flagged display irqs as disabled during runtime
PM transitions. So we can just check that flag to see if we should do
skip display irqs during irq setup.
During driver load display irqs will be flagged as enabled since we've
turned on the power well already, however the power well code will have
skipped the display irq setup since irq support as a whole wasn't yet
enabled when the power well was enabled. So we'll want to do the display
irq setup in that case.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94164
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-4-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>
Take a bigger hammer to the underrun suppression on ILK. Instead of
trying to suppress them at specific points in the modeset sequence just
silence them across the entire sequence. This gets rid of some underruns
at least on my ILK. Note that this changes SNB and IVB to follow the
same approach just to keep the code less convoluted. The difference is
that on those platforms we won't suppress CPU underruns for port A since
it doesn't seem to be necessary.
My ILK has port A eDP and two PCH HDMI ports, so I can't be sure this is
as effective on other PCH port types. Perhaps we still need some of
Daniel's extra vblank waits [2]?
I've still been able to trigger an underrun on the other pipe, but
fixing that perhaps needs the LP1+ disable trick I implemented here [1]
which never got merged.
A few details which hamper stress testing on my ILK are that sometimes
the PCH transcoder gets messed up and refuses to shut down, and sometimes
even the panel power sequencer apparently gets stuck on the always on
position.
[1] https://lists.freedesktop.org/archives/intel-gfx/2014-March/041317.html
[2] https://lists.freedesktop.org/archives/intel-gfx/2016-January/086397.html
v2: Add a note that we also get underruns when enabling PCH ports
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1459536799-18109-2-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Rather than blindly waking up all forcewake domains on command
submission, we can teach each engine what is (or are) the correct
one to take.
On platforms with multiple forcewake domains like VLV, CHV, SKL
and BXT, this has the potential of lowering the GPU and CPU
power use and submission latency.
To implement it we add a function named
intel_uncore_forcewake_for_reg whose purpose is to query which
forcewake domains need to be taken to read or write a specific
register with raw mmio accessors.
These enables the execlists engine setup to query which
forcewake domains are relevant per engine on the currently
running platform.
v2:
* Kerneldoc.
* Split from intel_uncore.c macro extraction, WARN_ON,
no warns on old platforms. (Chris Wilson)
v3:
* Single domain per engine, mention all registers,
bi-directional function and a new name, fix handling
of gen6 and gen7 writes. (Chris Wilson)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460468251-14069-1-git-send-email-tvrtko.ursulin@linux.intel.com
Chris Wilson points out that we can remove them from the array
since they are always written to with raw accessors.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Knowledge of which register per platform belonds in which
forcewake domain was embedded in the MMIO accessors themselves.
Extract it into standalone macros so they can be used from
new code in the following patches.
This causes GCC to compile some of the MMIO accessors slightly
differently and grows the code a tiny amount. But none of the
growth is on the fast-path so it does not matter hugely.
Affected sizes before:
00000000000026f0 00000000000001a5 t gen6_read16
0000000000002390 00000000000001a5 t gen6_read32
00000000000028a0 00000000000001a5 t gen6_read64
00000000000061d0 000000000000019e t gen8_write16
0000000000006510 000000000000019d t gen8_write32
0000000000006370 000000000000019d t gen8_write64
00000000000021f0 000000000000019d t gen8_write8
Affected sizes after:
0000000000002840 00000000000001aa t gen6_read16
00000000000024e0 00000000000001a9 t gen6_read32
00000000000029f0 00000000000001a9 t gen6_read64
0000000000004f20 00000000000001b5 t gen8_write16
0000000000004ba0 00000000000001b4 t gen8_write32
00000000000050e0 00000000000001b4 t gen8_write64
0000000000004d60 00000000000001b4 t gen8_write8
Other MMIO accessors are not affected in size.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
As the vast majority of users do not use the domain id variable,
we can eliminate it from the iterator and also change the latter
using the same principle as was recently done for for_each_engine.
For a couple of callers which do need the domain mask, store it
in the domain array (which already has the domain id), then both
can be retrieved thence.
Result is clearer code and smaller generated binary, especially
in the tight fw get/put loops. Also, relationship between domain
id and mask is no longer assumed in the macro.
v2: Improve grammar in the commit message and rename the
iterator to for_each_fw_domain_masked for consistency.
(Dave Gordon)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Dave Gordon <david.s.gordon@intel.com>
Because it is based on jiffies, current implementation releases the
forcewake at any time between straight away and between 1ms and 10ms,
depending on the kernel configuration (CONFIG_HZ).
This is probably not what has been desired, since the dynamics of keeping
parts of the GPU awake should not be correlated with this kernel
configuration parameter.
Change the auto-release mechanism to use hrtimers and set the timeout to
1ms with a 1ms of slack. This should make the GPU power consistent
across kernel configs, and timer slack should enable some timer coalescing
where multiple force-wake domains exist, or with unrelated timers.
For GlBench/T-Rex this decreases the number of forcewake releases from
~480 to ~300 per second, and for a heavy combined OGL/OCL test from
~670 to ~360 (HZ=1000 kernel).
Even though this reduction can be attributed to the average release period
extending from 0-1ms to 1-2ms, as discussed above, it will make the
forcewake timeout consistent for different CONFIG_HZ values.
Real life measurements with the above workload has shown that, with this
patch, both manage to auto-release the forcewake between 2-4 times per
10ms, even though the number of forcewake gets is dramatically different.
T-Rex requests between 5-10 explicit gets and 5-10 implict gets in each
10ms period, while the OGL/OCL test requests 250 and 380 times in the same
period.
The two data points together suggest that the nature of the forwake
accesses is bursty and that further changes and potential timeout
extensions, or moving the start of timeout from the first to the last
automatic forcewake grab, should be carefully measured for power and
performance effects.
v2:
* Commit spelling. (Dave Gordon)
* More discussion on numbers in the commit. (Chris Wilson)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Dave Gordon <david.s.gordon@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
We've had problems on several occasions with using the panel type
from the VBT block 40. Usually it seems to be 2, which often
doesn't give us the correct timings for the panel. After some
more digging I found a way to get a panel type via the OpRegion
SWSCI GBDA "Get Panel Details" method. Let's try to use it.
The spec has this to say about the output:
"Bits [15:8] - Panel Type
Bits contain the panel type user setting from CMOS
00h = Not Valid, use default Panel Type & Timings from VBT
01h - 0Fh = Panel Number"
Another version of the spec lists the valid range as 1-16, which makes
more sense since VBT supports 16 panels. Based on actual results
from Rob's G45, 1-16 is what we need to accept.
The other bits in the output don't look relevant for the problem at
hand.
The input is specified as:
"Bits [31:4] - Reserved
Reserved (must be zero)
Bits [3:0] - Panel Number
These bits contain the sequential index of Panel, starting at 0 and
counting upwards from the first integrated Internal Flat-Panel Display
Encoder present, and then from the first external Display Encoder
(e.g., S/DVO-B then S/DVO-C) which supports Internal Flat-Panels.
0h - 0Fh = Panel number"
For now I've just hardcoded the input panel number as 0. That would seem
like a decent choise for LVDS. Not so sure about eDP when port != A.
v2: Accept values 1-16
Filter out bogus results in opregion code (Jani)
Add debug logging for all the different branches (Jani)
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rob Kramer <rob@solution-space.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94825
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460359431-11003-1-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Rob Kramer <rob@solution-space.com>
When the GMBUS based i2c transfer times out, we try to fall back to
bit-banging and retry the operation that way. However if the bit-banging
attempt also fails, we should probably go back to the GMBUS method for
the next attempt. Maybe there simply wasn't anyone one the bus at this
time.
There's also a bit of a mess going on with the force_bit handling.
It's supposed to be a ref count actually, and it is as far as
intel_gmbus_force_bit() is concerned. But it's treated as just a
flag by the timeout based bit-banging fallback. I suppose that's
fine since we should never end up in the timeout fallback case
if force_bit was already non-zero. However now that we want to restore
things back to where they were after the bit-banging attempt failed,
we're going to have to do things a bit differently to avoid clobbering
the force_bit count as set up by intel_gmbus_force_bit(). So let's
dedicate the high bit as a flag for the low level timeout based fallback
and treat the rest of the bits as a ref count just as before.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457366220-29409-4-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
In order to ensure that all invalidations are completed before the
operation returns to userspace (i.e. before the munmap() syscall returns)
we need to wait upon the outstanding operations.
We are allowed to block inside the invalidate_range_start callback, and
as struct_mutex is the inner lock with mmap_sem we can wait upon the
struct_mutex without provoking lockdep into warning about a deadlock.
However, we don't actually want to wait upon outstanding rendering
whilst holding the struct_mutex if we can help it otherwise we also
block other processes from submitting work to the GPU. So first we do a
wait without the lock and then when we reacquire the lock, we double
check that everything is ready for removing the invalidated pages.
Finally to wait upon the outstanding unpinning tasks, we create a
private workqueue as a means to conveniently wait upon all at once. The
drawback is that this workqueue is per-mm, so any threads concurrently
invalidating objects will wait upon each other. The advantage of using
the workqueue is that we can wait in parallel for completion of
rendering and unpinning of several objects (of particular importance if
the process terminates with a whole mm full of objects).
v2: Apply a cup of tea to the changelog.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94699
Testcase: igt/gem_userptr_blits/sync-unmap-cycles
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459864801-28606-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Linux 4.6-rc3
Backmerge requested by Chris Wilson to make his patches apply cleanly.
Tiny conflict in vmalloc.c with the (properly acked and all) patch in
drm-intel-next:
commit 4da56b99d9
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon Apr 4 14:46:42 2016 +0100
mm/vmap: Add a notifier for when we run out of vmap address space
and Linus' tree.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
We now have two implementations for vmapping a whole object, one for
dma-buf and one for the ringbuffer. If we couple the mapping into the
obj->pages lifetime, then we can reuse an obj->mapping for both and at
the same time couple it into the shrinker. There is a third vmapping
routine in the cmdparser that maps only a range within the object, for
the time being that is left alone, but will eventually use these routines
in order to cache the mapping between invocations.
v2: Mark the failable kmalloc() as __GFP_NOWARN (vsyrjala)
v3: Call unpin_vmap from the right dmabuf unmapper
v4: Rename vmap to map as we don't wish to imply the type of mapping
involved, just that it contiguously maps the object into kernel space.
Add kerneldoc and lockdep annotations
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460113874-17366-4-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Pull ARM fixes from Russell King:
"A couple of small fixes, and wiring up the new syscalls which appeared
during the merge window"
* 'fixes' of git://ftp.arm.linux.org.uk/~rmk/linux-arm:
ARM: 8550/1: protect idiv patching against undefined gcc behavior
ARM: wire up preadv2 and pwritev2 syscalls
ARM: SMP enable of cache maintanence broadcast
Pull MMC fixes from Ulf Hansson:
"Here are a couple of mmc fixes intended for v4.6 rc3:
MMC host:
- sdhci: Fix regression setting power on Trats2 board
- sdhci-pci: Add support and PCI IDs for more Broxton host controllers"
* tag 'mmc-v4.6-rc1' of git://git.linaro.org/people/ulf.hansson/mmc:
mmc: sdhci-pci: Add support and PCI IDs for more Broxton host controllers
mmc: sdhci: Fix regression setting power on Trats2 board
Pull i2c fixes from Wolfram Sang:
"Some bugfixes from I2C:
- fix a uevent triggered boot problem by removing a useless debug
print
- fix sysfs-attributes of the new i2c-demux-pinctrl driver to follow
standard kernel behaviour
- fix a potential division-by-zero error (needed two takes)"
* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
i2c: jz4780: really prevent potential division by zero
Revert "i2c: jz4780: prevent potential division by zero"
i2c: jz4780: prevent potential division by zero
i2c: mux: demux-pinctrl: Update docs to new sysfs-attributes
i2c: mux: demux-pinctrl: Clean up sysfs attributes
i2c: prevent endless uevent loop with CONFIG_I2C_DEBUG_CORE
This reverts commit 1028b55baf.
It's broken: it makes ext4 return an error at an invalid point, causing
the readdir wrappers to write the the position of the last successful
directory entry into the position field, which means that the next
readdir will now return that last successful entry _again_.
You can only return fatal errors (that terminate the readdir directory
walk) from within the filesystem readdir functions, the "normal" errors
(that happen when the readdir buffer fills up, for example) happen in
the iterorator where we know the position of the actual failing entry.
I do have a very different patch that does the "signal_pending()"
handling inside the iterator function where it is allowable, but while
that one passes all the sanity checks, I screwed up something like four
times while emailing it out, so I'm not going to commit it today.
So my track record is not good enough, and the stars will have to align
better before that one gets committed. And it would be good to get some
review too, of course, since celestial alignments are always an iffy
debugging model.
IOW, let's just revert the commit that caused the problem for now.
Reported-by: Greg Thelen <gthelen@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull parisc fixes from Helge Deller:
"Since commit 0de798584b ("parisc: Use generic extable search and
sort routines") module loading is boken on parisc, because the parisc
module loader wasn't prepared for the new R_PARISC_PCREL32 relocations.
In addition, due to that breakage, Mikulas Patocka noticed that
handling exceptions from modules probably never worked on parisc. It
was just masked by the fact that exceptions from modules don't happen
during normal use.
This patch series fixes those issues and survives the tests of the
lib/test_user_copy kernel module test. Some patches are tagged for
stable"
* 'parisc-4.6-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Update comment regarding relative extable support
parisc: Unbreak handling exceptions from kernel modules
parisc: Fix kernel crash with reversed copy_from_user()
parisc: Avoid function pointers for kernel exception routines
parisc: Handle R_PARISC_PCREL32 relocations in kernel modules
Pull libnvdimm fixes from Dan Williams:
"Three fixes, the first two are tagged for -stable:
- The ndctl utility/library gained expanded unit tests illuminating a
long standing bug in the libnvdimm SMART data retrieval
implementation.
It has been broken since its initial implementation, now fixed.
- Another one line fix for the detection of stale info blocks.
Without this change userspace can get into a situation where it is
unable to reconfigure a namespace.
- Fix the badblock initialization path in the presence of the new (in
v4.6-rc1) section alignment workarounds.
Without this change badblocks will be reported at the wrong offset.
These have received a build success report from the kbuild robot and
have appeared in -next with no reported issues"
* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
libnvdimm, pfn: fix nvdimm_namespace_add_poison() vs section alignment
libnvdimm, pfn: fix uuid validation
libnvdimm: fix smart data retrieval
Pull GPIO fixes from Linus Walleij:
"Here is a set of four GPIO fixes. The two fixes to the core are
serious as they are regressing minor architectures.
Core fixes:
- Defer GPIO device setup until after gpiolib is initialized.
It turns out that a few very tightly integrated GPIO platform
drivers initialize so early (befor core_initcall()) so that the
gpiolib isn't even initialized itself. That limits what the
library can do, and we cannot reference uninitialized fields until
later.
Defer some of the initialization until right after the gpiolib is
initialized in these (rare) cases.
- As a consequence: do not use devm_* resources when allocating the
states in the initial set-up of the gpiochip.
Driver fixes:
- In ACPI retrieveal: ignore GpioInt when looking for output GPIOs.
- Fix legacy builds on the PXA without a backing pin controller.
- Use correct datatype on pca953x register writes"
* tag 'gpio-v4.6-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio:
gpio: pca953x: Use correct u16 value for register word write
gpiolib: Defer gpio device setup until after gpiolib initialization
gpiolib: Do not use devm functions when registering gpio chip
gpio: pxa: fix legacy non pinctrl aware builds
gpio / ACPI: ignore GpioInt() GPIOs when requesting GPIO_OUT_*
Pull tty fixes from Greg KH:
"Here are two tty fixes for issues found.
One was due to a merge error in 4.6-rc1, and the other a regression
fix for UML consoles that broke in 4.6-rc1.
Both have been in linux-next for a while"
* tag 'tty-4.6-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
tty: Fix merge of "tty: Refactor tty_open()"
tty: Fix UML console breakage
Pull USB fixes from Greg KH:
"Here are some USB fixes and new device ids for 4.6-rc3.
Nothing major, the normal USB gadget fixes and usb-serial driver ids,
along with some other fixes mixed in. All except the USB serial ids
have been tested in linux-next, the id additions should be fine as
they are 'trivial'"
* tag 'usb-4.6-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (25 commits)
USB: option: add "D-Link DWM-221 B1" device id
USB: serial: cp210x: Adding GE Healthcare Device ID
USB: serial: ftdi_sio: Add support for ICP DAS I-756xU devices
usb: dwc3: keystone: drop dma_mask configuration
usb: gadget: udc-core: remove manual dma configuration
usb: dwc3: pci: add ID for one more Intel Broxton platform
usb: renesas_usbhs: fix to avoid using a disabled ep in usbhsg_queue_done()
usb: dwc2: do not override forced dr_mode in gadget setup
usb: gadget: f_midi: unlock on error
USB: digi_acceleport: do sanity checking for the number of ports
USB: cypress_m8: add endpoint sanity check
USB: mct_u232: add sanity checking in probe
usb: fix regression in SuperSpeed endpoint descriptor parsing
USB: usbip: fix potential out-of-bounds write
usb: renesas_usbhs: disable TX IRQ before starting TX DMAC transfer
usb: renesas_usbhs: avoid NULL pointer derefernce in usbhsf_pkt_handler()
usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize
usb: phy: qcom-8x16: fix regulator API abuse
usb: ch9: Fix SSP Device Cap wFunctionalitySupport type
usb: gadget: composite: Access SSP Dev Cap fields properly
...
Pull staging and IIO driver fixes from Greg KH:
"Here are some IIO driver fixes, along with two staging driver fixes
for 4.6-rc3.
One staging driver patch reverts the deletion of a driver that
happened in 4.6-rc1. We thought that laptop.org was dead, but it's
still alive and kicking, and has users that were mad we broke their
hardware by deleting a driver for their machines. So that driver is
added back and everyone is happy again.
All of these have been in linux-next for a while with no reported
issues"
* tag 'staging-4.6-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
Revert "Staging: olpc_dcon: Remove obsolete driver"
staging/rdma/hfi1: select CRC32
iio: gyro: bmg160: fix buffer read values
iio: gyro: bmg160: fix endianness when reading axes
iio: accel: bmc150: fix endianness when reading axes
iio: st_magn: always define ST_MAGN_TRIGGER_SET_STATE
iio: fix config watermark initial value
iio: health: max30100: correct FIFO check condition
iio: imu: Fix inv_mpu6050 dependencies
iio: adc: Fix build error of missing devm_ioremap_resource on UM
iio: light: apds9960: correct FIFO check condition
iio: adc: max1363: correct reference voltage
iio: adc: max1363: add missing adc to max1363_id
Pull SCSI fixes from James Bottomley:
"This is a set of eight fixes.
Two are trivial gcc-6 updates (brace additions and unused variable
removal). There's a couple of cxlflash regressions, a correction for
sd being overly chatty on revalidation (causing excess log increases).
A VPD issue which could crash USB devices because they seem very
intolerant to VPD inquiries, an ALUA deadlock fix and a mpt3sas buffer
overrun fix"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: Do not attach VPD to devices that don't support it
sd: Fix excessive capacity printing on devices with blocks bigger than 512 bytes
scsi_dh_alua: Fix a recently introduced deadlock
scsi: Declare local symbols static
cxlflash: Move to exponential back-off when cmd_room is not available
cxlflash: Fix regression issue with re-ordering patch
mpt3sas: Don't overreach ioc->reply_post[] during initialization
aacraid: add missing curly braces
Pull MD fixes from Shaohua Li:
"This update mainly fixes bugs:
- fix error handling (Guoqing)
- fix a crash when a disk is hotremoved (me)
- fix a dead loop (Wei Fang)"
* tag 'md/4.6-rc2-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md:
md/bitmap: clear bitmap if bitmap_create failed
MD: add rdev reference for super write
md: fix a trivial typo in comments
md:raid1: fix a dead loop when read from a WriteMostly disk
