Current Intel SVM is designed by setting the pgd_t of the processor page
table to FLPTR field of the PASID entry. The first level translation only
supports 4 and 5 level paging structures, hence it's infeasible for the
IOMMU to share a processor's page table when it's running in 32-bit mode.
Let's disable 32bit support for now and claim support only when all the
missing pieces are ready in the future.

Fixes: 1c4f88b7 ("iommu/vt-d: Shared virtual address in scalable mode")
Suggested-by: NJoerg Roedel <jroedel@suse.de>
Signed-off-by: NLu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20200622231345.29722-2-baolu.lu@linux.intel.comSigned-off-by: NJoerg Roedel <jroedel@suse.de>

Use the correct the function name in the documentation for
"pcs_parse_one_pinctrl_entry()".

"smux_parse_one_pinctrl_entry()" appears to be an artifact from the
development of a prior patch series ("simple pinmux driver") which
transformed into pinctrl-single.
Signed-off-by: NDrew Fustini <drew@beagleboard.org>
Link: https://lore.kernel.org/r/20200612112758.GA3407886@x1Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

The patch adds missing qpic data pins to qpic pingroup. These pins are
necessary for the qpic nand to work.

Fixes: ef1ea54e ("pinctrl: qcom: Add ipq6018 pinctrl driver")
Signed-off-by: NSivaprakash Murugesan <sivaprak@codeaurora.org>
Link: https://lore.kernel.org/r/1592541089-17700-1-git-send-email-sivaprak@codeaurora.orgSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

Revert "pinctrl: freescale: imx: Use 'devm_of_iomap()' to avoid a resource leak in case of error in 'imx_pinctrl_probe()'"

This reverts commit ba403242.

After commit 26d8cde5 ("pinctrl: freescale: imx: add shared
input select reg support"). i.MX7D has two iomux controllers
iomuxc and iomuxc-lpsr which share select_input register for
daisy chain settings.
If use 'devm_of_iomap()', when probe the iomuxc-lpsr, will call
devm_request_mem_region() for the region <0x30330000-0x3033ffff>
for the first time. Then, next time when probe the iomuxc, API
devm_platform_ioremap_resource() will also use the API
devm_request_mem_region() for the share region <0x30330000-0x3033ffff>
again, then cause issue, log like below:

[    0.179561] imx7d-pinctrl 302c0000.iomuxc-lpsr: initialized IMX pinctrl driver
[    0.191742] imx7d-pinctrl 30330000.pinctrl: can't request region for resource [mem 0x30330000-0x3033ffff]
[    0.191842] imx7d-pinctrl: probe of 30330000.pinctrl failed with error -16

Fixes: ba403242 ("pinctrl: freescale: imx: Use 'devm_of_iomap()' to avoid a resource leak in case of error in 'imx_pinctrl_probe()'")
Signed-off-by: NHaibo Chen <haibo.chen@nxp.com>
Reviewed-by: NDong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/1591673223-1680-1-git-send-email-haibo.chen@nxp.comSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

Fix spelling mistake in the comments with help of `codespell`.
seperate ==> separate
Signed-off-by: NKeyur Patel <iamkeyur96@gmail.com>
Signed-off-by: NWolfram Sang <wsa@kernel.org>

All in-tree users have been converted to the new i2c_new_client_device
function, so remove this deprecated one.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: NWolfram Sang <wsa@kernel.org>

Move away from the deprecated API and return the shiny new ERRPTR where
useful.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NDaniel Thompson <daniel.thompson@linaro.org>
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NWolfram Sang <wsa@kernel.org>

i2c_new_client() is deprecated, use the replacement
i2c_new_client_device(). Also, we have a helper to check if a driver is
bound. Use it to simplify the code. Note that this changes the errno for
a failed device creation from ENOMEM to ENODEV. No callers currently
interpret this errno, though, so we use this condensed error check.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NWolfram Sang <wsa@kernel.org>

module_put() balances try_module_get(), not request_module(). Fix the
error path to match that.

Fixes: 2066facc ("drm/kms: slave encoder interface.")
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NWolfram Sang <wsa@kernel.org>

When a filesystem is mounted on a loop device and on a loop ioctl
LOOP_SET_STATUS64, because of kill_bdev, buffer_head mappings are getting
destroyed.
kill_bdev
  truncate_inode_pages
    truncate_inode_pages_range
      do_invalidatepage
        block_invalidatepage
          discard_buffer  -->clear BH_Mapped flag

sb_bread
  __bread_gfp
  bh = __getblk_gfp
  -->discard_buffer clear BH_Mapped flag
  __bread_slow
    submit_bh
      submit_bh_wbc
        BUG_ON(!buffer_mapped(bh))  --> hit this BUG_ON

Fixes: 5db470e2 ("loop: drop caches if offset or block_size are changed")
Signed-off-by: NZheng Bin <zhengbin13@huawei.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Commit 130f4caf ("libata: Ensure ata_port probe has completed before
detach") may cause system freeze during suspend.

Using async_synchronize_full() in PM callbacks is wrong, since async
callbacks that are already scheduled may wait for not-yet-scheduled
callbacks, causes a circular dependency.

Instead of using big hammer like async_synchronize_full(), use async
cookie to make sure port probe are synced, without affecting other
scheduled PM callbacks.

Fixes: 130f4caf ("libata: Ensure ata_port probe has completed before detach")
Suggested-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NKai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: NJohn Garry <john.garry@huawei.com>
BugLink: https://bugs.launchpad.net/bugs/1867983Signed-off-by: NJens Axboe <axboe@kernel.dk>

Add rename the gpu busy percentage for consistency and
add the mem busy percentage documentation.
Reviewed-by: NEvan Quan <evan.quan@amd.com>
Reviewed-by: NNirmoy Das <nirmoy.das@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

Vega10 and previous asics use one interface, vega20 and newer
use another.
Reviewed-by: NEvan Quan <evan.quan@amd.com>
Acked-by: NNirmoy Das <nirmoy.das@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

The existing code used the major version number of the DRM driver
instead of the device major number of the DRM subsystem for
validating access for a devices cgroup.

This meant that accesses allowed by the devices cgroup weren't
permitted and certain accesses denied by the devices cgroup were
permitted (if they matched the wrong major device number).
Signed-off-by: NLorenz Brun <lorenz@brun.one>
Fixes: 6b855f7b ("drm/amdkfd: Check against device cgroup")
Reviewed-off-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

It is possible that a platform that is capable of 'namespace labels'
comes up without the labels properly initialized. In this case, the
region's 'align' attribute is hidden. Howerver, once the user does
initialize he labels, the 'align' attribute still stays hidden, which is
unexpected.

The sysfs_update_group() API is meant to address this, and could be
called during region probe, but it has entanglements with the device
'lockdep_mutex'. Therefore, simply make the 'align' attribute always
visible. It doesn't matter what it says for label-less namespaces, since
it is not possible to change their allocation anyway.
Suggested-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NVishal Verma <vishal.l.verma@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/20200520225026.29426-1-vishal.l.verma@intel.comSigned-off-by: NDan Williams <dan.j.williams@intel.com>

The way we produce SBALs to the device (first update q->nr_buf_used,
then update the SLSB) should ensure that we never see some of the
SLSB states when scanning the queue for progress.
So make some noise if we do, this implies a bug in our SBAL tracking.

Also tweak the WARN msg to provide more information.
Signed-off-by: NJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

This removes the last remaining accesses to ->qdio_data from internal
code. Just pass the qdio_irq struct where needed instead.
Signed-off-by: NJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

Better describe what these functions do.
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The CONFIG_PM_SLEEP #ifdef checks in this file are inconsistent,
leading to a warning about sometimes unused function:

drivers/net/ethernet/intel/e1000e/netdev.c:137:13: error: unused function 'e1000e_check_me' [-Werror,-Wunused-function]

Rather than adding more #ifdefs, just remove them completely
and mark the PM functions as __maybe_unused to let the compiler
work it out on it own.

Fixes: e086ba2f ("e1000e: disable s0ix entry and exit flows for ME systems")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Tested-by: NAaron Brown <aaron.f.brown@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

With legacy PM hooks, it was the responsibility of a driver to manage PCI
states and also the device's power state. The generic approach is to let PCI
core handle the work.

e1000_suspend() calls __e1000_shutdown() to perform intermediate tasks.
__e1000_shutdown() modifies the value of "wake" (device should be wakeup
enabled or not), responsible for controlling the flow of legacy PM.

Since, PCI core has no idea about the value of "wake", new code for generic
PM may produce unexpected results. Thus, use "device_set_wakeup_enable()"
to wakeup-enable the device accordingly.
Signed-off-by: NVaibhav Gupta <vaibhavgupta40@gmail.com>
Tested-by: NAaron Brown <aaron.f.brown@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

Currently the system will be woken up via WOL(Wake On LAN) even if the
device wakeup ability has been disabled via sysfs:
 cat /sys/devices/pci0000:00/0000:00:1f.6/power/wakeup
 disabled

The system should not be woken up if the user has explicitly
disabled the wake up ability for this device.

This patch clears the WOL ability of this network device if the
user has disabled the wake up ability in sysfs.

Fixes: bc7f75fa ("[E1000E]: New pci-express e1000 driver")
Reported-by: N"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: NChen Yu <yu.c.chen@intel.com>
Tested-by: NAaron Brown <aaron.f.brown@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

Without a MODULE_DEVICE_TABLE the attributes are missing that create
an alias for auto-loading the module in userspace via hotplug.
Signed-off-by: NTim Harvey <tharvey@gateworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The port's headroom buffers are used to store packets while they
traverse the device's pipeline and also to store packets that are egress
mirrored.

On Spectrum-3, ports with eight lanes use two headroom buffers between
which the configured headroom size is split.

In order to prevent packet loss, multiply the calculated headroom size
by two for 8x ports.

Fixes: da382875 ("mlxsw: spectrum: Extend to support Spectrum-3 ASIC")
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Reviewed-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Code to initialize the conf structure while gathering the configuration
of the device was missing.

Fixes: 571912c6 ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: NMartin <martin.varghese@nokia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The remove function does not destroy all
BM Pools when per cpu pool is active.

When reloading the mvpp2 as a module the BM Pools
are still active in hardware and due to the bug
have twice the size now old + new.

This eventually leads to a kernel crash.

v2:
* add Fixes tag

Fixes: 7d04b0b1 ("mvpp2: percpu buffers")
Signed-off-by: NSven Auhagen <sven.auhagen@voleatech.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

osd_req_flags is overly general and doesn't suit its only user
(read_from_replica option) well:

- applying osd_req_flags in account_request() affects all OSD
  requests, including linger (i.e. watch and notify).  However,
  linger requests should always go to the primary even though
  some of them are reads (e.g. notify has side effects but it
  is a read because it doesn't result in mutation on the OSDs).

- calls to class methods that are reads are allowed to go to
  the replica, but most such calls issued for "rbd map" and/or
  exclusive lock transitions are requested to be resent to the
  primary via EAGAIN, doubling the latency.

Get rid of global osd_req_flags and set read_from_replica flag
only on specific OSD requests instead.

Fixes: 8ad44d5e ("libceph: read_from_replica option")
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Reviewed-by: NJeff Layton <jlayton@kernel.org>

This patch fixes below warning reported by coccicheck

drivers/s390/crypto/zcrypt_ep11misc.c:198:8-15: WARNING:
kzalloc should be used for cprb, instead of kmalloc/memset

Link: https://lkml.kernel.org/r/1587472548-105240-1-git-send-email-zou_wei@huawei.comReported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NZou Wei <zou_wei@huawei.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

Support for hibernation on s390 has been recently been removed with
commit 39421627 ("s390: remove broken hibernate / power management
support"), no need to keep unused code around.

Link: https://lkml.kernel.org/r/20200526093629.257649-1-cohuck@redhat.comSigned-off-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NHalil Pasic <pasic@linux.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

Streamline the processing of QDIO Input Queues, and remove some
intermittent SLSB updates (no deleting of old ACKs, no redundant
transitions through NOT_INIT).

Rather than counting ACKs, we now keep track of the whole batch of
SBALs that were completed during the current polling cycle.
Most completed SBALs stay in their initial state (ie. PRIMED or ERROR),
except that the most recent SBAL in each sub-run is ACKed for
IRQ reduction.

The only logic changes happen in inbound_handle_work(), the other
delta is just a renaming of the variables that track the SBAL batch.

Note that in particular we don't need to flip the _oldest_ SBAL to
an idle state (eg. NOT_INIT or ACKed) as a guard against catching our
own tail. Since get_inbound_buffer_frontier() will never scan more than
the remaining nr_buf_used SBALs, this scenario just doesn't occur.
Signed-off-by: NJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

xchg() for a single-byte location assembles to a 4-byte Compare&Swap,
wrapped into a non-trivial amount of retry code that deals with
concurrent modifications to the unaffected bytes.

Change it to a simple byte-store, but preserve the memory ordering
semantics that the CS provided.
This simplifies the generated code for a hot path, and in theory also
allows us to amortize the memory barriers over multiple SLSB updates.

CC: Andreas Krebbel <krebbel@linux.ibm.com>
Signed-off-by: NJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

For all ddi, encoder->type holds output type as ddi,
assigning it to individual o/p types is no more valid.

Fixes: 362bfb99 ("drm/i915/tgl: Add DKL PHY vswing table for HDMI")

v2: Rebase, no functional change.
Signed-off-by: NVandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: NUma Shankar <uma.shankar@intel.com>
Signed-off-by: NUma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200612082237.11886-1-vandita.kulkarni@intel.com
(cherry picked from commit 94641eb6)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Atm, hotplug interrupts on TypeC ports are left enabled after detecting
an interrupt storm, fix this.
Reported-by: NKunal Joshi <kunal1.joshi@intel.com>
References: https://gitlab.freedesktop.org/drm/intel/-/issues/351
Bugzilla: https://gitlab.freedesktop.org/drm/intel/-/issues/1964
Cc: Kunal Joshi <kunal1.joshi@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200612121731.19596-1-imre.deak@intel.com
(cherry picked from commit 587a87b9)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Rescue the GT workarounds from being buried inside init_clock_gating so
that we remember to apply them after a GT reset, and that they are
included in our verification that the workarounds are applied.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200611080140.30228-6-chris@chris-wilson.co.uk
(cherry picked from commit 2bcefd0d)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Rescue the GT workarounds from being buried inside init_clock_gating so
that we remember to apply them after a GT reset, and that they are
included in our verification that the workarounds are applied.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200611080140.30228-5-chris@chris-wilson.co.uk
(cherry picked from commit 806a45c0)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Rescue the GT workarounds from being buried inside init_clock_gating so
that we remember to apply them after a GT reset, and that they are
included in our verification that the workarounds are applied.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200611080140.30228-4-chris@chris-wilson.co.uk
(cherry picked from commit c3b93a94)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Rescue the GT workarounds from being buried inside init_clock_gating so
that we remember to apply them after a GT reset, and that they are
included in our verification that the workarounds are applied.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200611080140.30228-3-chris@chris-wilson.co.uk
(cherry picked from commit 7331c356)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Rescue the GT workarounds from being buried inside init_clock_gating so
that we remember to apply them after a GT reset, and that they are
included in our verification that the workarounds are applied.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200611080140.30228-2-chris@chris-wilson.co.uk
(cherry picked from commit 19f1f627)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Rescue the GT workarounds from being buried inside init_clock_gating so
that we remember to apply them after a GT reset, and that they are
included in our verification that the workarounds are applied.

v2: Leave HSW_SCRATCH to set an explicit value, not or in our disable
bit.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2011Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200611093015.11370-1-chris@chris-wilson.co.uk
(cherry picked from commit f93ec5fb)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

According to BSpec the Data Island Packet should be disabled after
disabling the transcoder, but before the transcoder clock select is set
to none. On an ICL RVP, daisy-chained MST config not following this
leads to a hang with the following MCE when disabling the output:

[  870.948739] mce: [Hardware Error]: CPU 0: Machine Check Exception: 5 Bank 6: ba00000011000402
[  871.019212] mce: [Hardware Error]: RIP !INEXACT! 10:<ffffffff81aca652> {poll_idle+0x92/0xb0}
[  871.019212] mce: [Hardware Error]: TSC 135a261fe61
[  871.019212] mce: [Hardware Error]: PROCESSOR 0:706e5 TIME 1591739604 SOCKET 0 APIC 0 microcode 20
[  871.019212] mce: [Hardware Error]: Run the above through 'mcelog --ascii'
[  871.019212] mce: [Hardware Error]: Machine check: Processor context corrupt
[  871.019212] Kernel panic - not syncing: Fatal machine check
[  871.019212] Kernel Offset: disabled

Bspec: 4287

Fixes: fa37a213 ("drm/i915: Stop sending DP SDPs on ddi disable")
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NUma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200609220616.6015-1-imre.deak@intel.com
(cherry picked from commit c980216d)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

In commit 5ba32c7b ("drm/i915/execlists: Always force a context
reload when rewinding RING_TAIL"), we placed the check for rewinding a
context on actually submitting the next request in that context. This
was so that we only had to check once, and could do so with precision
avoiding as many forced restores as possible. For example, to ensure
that we can resubmit the same request a couple of times, we include a
small wa_tail such that on the next submission, the ring->tail will
appear to move forwards when resubmitting the same request. This is very
common as it will happen for every lite-restore to fill the second port
after a context switch.

However, intel_ring_direction() is limited in precision to movements of
upto half the ring size. The consequence being that if we tried to
unwind many requests, we could exceed half the ring and flip the sense
of the direction, so missing a force restore. As no request can be
greater than half the ring (i.e. 2048 bytes in the smallest case), we
can check for rollback incrementally. As we check against the tail that
would be submitted, we do not lose any sensitivity and allow lite
restores for the simple case. We still need to double check upon
submitting the context, to allow for multiple preemptions and
resubmissions.

Fixes: 5ba32c7b ("drm/i915/execlists: Always force a context reload when rewinding RING_TAIL")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: <stable@vger.kernel.org> # v5.4+
Reviewed-by: NBruce Chang <yu.bruce.chang@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200609151723.12971-1-chris@chris-wilson.co.uk
(cherry picked from commit e36ba817)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>