In the current code, at haswell_modeset_global_resources, first we
decide if we want to enable/disable the power well, then we decide if
we want to enable/disable PC8. On the case where we're enabling PC8
this works fine, but on the case where we disable PC8 due to a non-eDP
monitor being enabled, we first enable the power well and then disable
PC8. Although wrong, this doesn't seem to be causing any problems now,
and we don't even see anything in dmesg. But the patches for runtime
D3 turn this problem into a real bug, so we need to fix it.

This fixes the "modeset-non-lpsp" subtest from the "pm_pc8" test from
intel-gpu-tools.

v2: - Rebase (i915_disable_power_well).
v3: - More reabase.
v4: - Rebase on top of -fixes instead of -nightly.

This is commit d62292c8 in -next, but
we need it in -fixes to address Dave's report.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Reported-by: NDave Jones <davej@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Currently, PC8 is enabled at modeset_global_resources, which is called
after intel_modeset_update_state. Due to this, there's a small race
condition on the case where we start enabling PC8, then do a modeset
while PC8 is still being enabled. The racing condition triggers a WARN
because intel_modeset_update_state will mark the CRTC as enabled, then
the thread that's still enabling PC8 might look at the data structure
and think that PC8 is being enabled while a pipe is enabled. Despite
the WARN, this is not really a bug since we'll wait for the
PC8-enabling thread to finish when we call modeset_global_resources.

The spec says the CRTC cannot be enabled when we disable LCPLL, so we
had a check for crtc->base.enabled. If we change to crtc->active we
will still prevent disabling LCPLL while the CRTC is enabled, and we
will also prevent the WARN above.

This is a replacement for the previous patch named
    "drm/i915: get/put PC8 when we get/put a CRTC"

Testcase: igt/pm_pc8/modeset-lpsp-stress-no-wait
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
(cherry picked from commit 798183c5
from -next due to Dave's report.)
Reported-by: NDave Jones <davej@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

As the rings may be processed and their requests deallocated in a
different order to the natural retirement during a reset,

/* Whilst this request exists, batch_obj will be on the
 * active_list, and so will hold the active reference. Only when this
 * request is retired will the the batch_obj be moved onto the
 * inactive_list and lose its active reference. Hence we do not need
 * to explicitly hold another reference here.
 */

is violated, and the batch_obj may be dereferenced after it had been
freed on another ring. This can be simply avoided by processing the
status update prior to deallocating any requests.

Fixes regression (a possible OOPS following a GPU hang) from
commit aa60c664
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Wed Jun 12 15:13:20 2013 +0300

    drm/i915: find guilty batch buffer on ring resets
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
[danvet: Add the code comment Chris supplied.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Whilst looking up the objects required for an execbuffer, an untimely
allocation failure in creating the vma results in the object being
unreferenced from two lists. The ownership during the lookup is meant to
be moved from the list of objects being looked to the vma, and this
double unreference upon error results in a use-after-free.

Fixes regression from
commit 27173f1f
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Wed Aug 14 11:38:36 2013 +0200

    drm/i915: Convert execbuf code to use vmas

Based on the fix by Ben Widawsky.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: stable@vger.kernel.org
[danvet: Bikeshed the crucial comment above the ownership transfer as
discussed on irc.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

These four patches fix a few issues discovered since the initial merge,
which have been reviewed by Rob Clark and Thierry Reding.

* 'drm-tda998x-3.12-fixes' of git://ftp.arm.linux.org.uk/~rmk/linux-cubox:
  DRM: Armada: prime refcounting bug fix
  DRM: Armada: fix printing of phys_addr_t/dma_addr_t
  DRM: Armada: destroy framebuffer after helper
  DRM: Armada: implement lastclose() for fbhelper

Merge tag 'drm-intel-fixes-2013-12-11' of git://people.freedesktop.org/~danvet/drm-intel into drm-fixes

Just a bunch of regression fixes plus a few patches for long-standing
issues in gem corner-cases that we've hunted down in the past weeks. Since
apparently people hit those in the wild (and we also have nice igts for
them) I've opted for -fixes and cc: stable.

There's 1-2 things oustanding on top of this where I'm still waiting on
confirmation from testing, but nothing really scary.

* tag 'drm-intel-fixes-2013-12-11' of git://people.freedesktop.org/~danvet/drm-intel:
  drm/i915: don't update the dri1 breadcrumb with modesetting
  drm/i915: Repeat eviction search after idling the GPU
  drm/i915: Fix use-after-free in do_switch
  drm/i915: fix pm init ordering
  drm/i915: Hold mutex across i915_gem_release
  drm/i915: Skip clock checks on BDW
  drm/i915: Do not clobber config status after a forced restore of hw state
  drm/i915: Take modeset locks around intel_modeset_setup_hw_state()

As promised bdw fixes come separate for now. Just a few minior things.

* 'bdw-fixes' of git://people.freedesktop.org/~danvet/drm-intel:
  drm/i915/bdw: PIPE_[BC] I[ME]R moved to powerwell
  drm/i915/bdw: Limit GTT to 2GB
  drm/i915/bdw: Add comment about gen8 HWS PGA
  drm/i915/bdw: Free correct number of ppgtt pages
  drm/i915/bdw: Do gen6 style reset for gen8
  drm/i915/bdw: GEN8 backlight support
  drm/i915/bdw: Add BDW to ULT macro

The update is horribly racy since it doesn't protect at all against
concurrent closing of the master fd. And it can't really since that
requires us to grab a mutex.

Instead of jumping through hoops and offloading this to a worker
thread just block this bit of code for the modesetting driver.

Note that the race is fairly easy to hit since we call the breadcrumb
function for any interrupt. So the vblank interrupt (which usually
keeps going for a bit) is enough. But even if we'd block this and only
update the breadcrumb for user interrupts from the CS we could hit
this race with kms/gem userspace: If a non-master is waiting somewhere
(and hence has interrupts enabled) and the master closes its fd
(probably due to crashing).

v2: Add a code comment to explain why fixing this for real isn't
really worth it. Also improve the commit message a bit.

v3: Fix the spelling in the comment.
Reported-by: NEugene Shatokhin <eugene.shatokhin@rosalab.ru>
Cc: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>
Cc: stable@vger.kernel.org
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Tested-by: NEugene Shatokhin <eugene.shatokhin@rosalab.ru>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Commit 011c2282 changed the way refcounting on imported dma_bufs
works, and this hadn't been spotted while forward-porting Armada.
Reflect the changes in that commit into the Armada driver.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

These can be 64-bit quantities, so fix them up appropriately.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Destroy the framebuffer only after the helper, since the helper may
still be referencing the framebufer at this point.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Call drm_fb_helper_restore_fbdev_mode() upon last close so that in the
event of the X server crashing, we have some kind of mode restored.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Pull watchdog fixes from Wim Van Sebroeck:
 "Drop the unnecessary miscdevice.h includes that we forgot in commit
  487722cf ("watchdog: Get rid of MODULE_ALIAS_MISCDEV statements")
  and fix an oops for the sc1200_wdt driver"

* git://www.linux-watchdog.org/linux-watchdog:
  sc1200_wdt: Fix oops
  watchdog: Drop unnecessary include of miscdevice.h

Pull AVR32 fixes from Hans-Christian Egtvedt.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/egtvedt/linux-avr32:
  avr32: favr-32: clk_round_rate() can return a zero upon error
  avr32: remove deprecated IRQF_DISABLED
  cpufreq_ at32ap-cpufreq.c: Fix section mismatch
  avr32: pm: Fix section mismatch
  avr32: Kill CONFIG_MTD_PARTITIONS

Pull s390 fixes from Martin Schwidefsky:
 "One patch to increase the number of possible CPUs to 256, with the
  latest machine a single LPAR can have up to 101 CPUs.  Plus a number
  of bug fixes, the clock_gettime patch fixes a regression added in the
  3.13 merge window"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/time,vdso: fix clock_gettime for CLOCK_MONOTONIC
  s390/vdso: ectg gettime support for CLOCK_THREAD_CPUTIME_ID
  s390/vdso: fix access-list entry initialization
  s390: increase CONFIG_NR_CPUS limit
  s390/smp,sclp: fix size of sclp_cpu_info structure
  s390/sclp: replace uninitialized early_event_mask_sccb variable with sccb_early
  s390/dasd: fix memory leak caused by dangling references to request_queue

If loaded with isapnp = 0 the driver explodes. This is catching
people out now and then. What should happen in the working case is
a complete mystery and the code appears terminally confused, but we
can at least make the error path work properly.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>
Partially-Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=53991

After commit 487722cf (watchdog: Get rid of MODULE_ALIAS_MISCDEV
statements) the affected drivers no longer need to include miscdevice.h.
Only exception is rt2880_wdt.c which never needed it.
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Reviewed-by: NJean Delvare <jdelvare@suse.de>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>

Treat both negative and zero return values from clk_round_rate() as
errors.  This is needed since subsequent patches will convert
clk_round_rate()'s return value to be an unsigned type, rather than a
signed type, since some clock sources can generate rates higher than
(2^31)-1 Hz.

Eventually, when calling clk_round_rate(), only a return value of zero
will be considered a error.  All other values will be considered valid
rates.  The comparison against values less than 0 is kept to preserve
the correct behavior in the meantime.
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Håvard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: NHans-Christian Egtvedt <egtvedt@samfundet.no>

This patch proposes to remove the use of the IRQF_DISABLED flag

It's a NOOP since 2.6.35 and it will be removed one day.
Signed-off-by: NMichael Opdenacker <michael.opdenacker@free-electrons.com>
Acked-by: NHans-Christian Egtvedt <egtvedt@samfundet.no>

The function at32_cpufreq_driver_init was marked as __init but will be
called from inside the cpufreq framework. This lead to the following a
section mismatch during compilation:

WARNING: drivers/built-in.o(.data+0x2448): Section mismatch in reference
from the variable at32_driver to the function
.init.text:at32_cpufreq_driver_init()
The variable at32_driver references
the function __init at32_cpufreq_driver_init()
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the
variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console
Signed-off-by: NMatthias Brugger <matthias.bgg@gmail.com>

The power management has a section mismatch which leads to the following
warning during compilation:

WARNING: arch/avr32/mach-at32ap/built-in.o(.text+0x16d4): Section
mismatch in reference from the function avr32_pm_offset() to the
function .init.text:pm_exception()
The function avr32_pm_offset() references
the function __init pm_exception().
Signed-off-by: NMatthias Brugger <matthias.bgg@gmail.com>
Acked-by: NHans-Christian Egtvedt <hegtvedt@cisco.com>

This patch removes CONFIG_MTD_PARTITIONS in config files for avr32.
Because CONFIG_MTD_PARTITIONS was removed by commit
6a8a98b2.
Signed-off-by: NEunbong Song <eunb.song@samsung.com>
Acked-by: NHans-Christian Egtvedt <hegtvedt@cisco.com>

With the advent of hw context support, we gained some objects that are
pinned for the duration of their request. That is we can make aperture
space available by idling the GPU and in the process performing a
context switch back to the always-pinned default context. As such, we
should not conclude that there is no space in the aperture for the
current object until we have unpinned any such context objects.

Note that we also have the problem of outstanding pageflips preventing
eviction of their framebuffer objects to resolve.

Testcase: igt/gem_ctx_exec/eviction
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=72507Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Tested-by: Nlu hua <huax.lu@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Pull powerpc fixes from Ben Herrenschmidt:
 "Here are a handful of powerpc fixes for 3.13.

  The patches are reasonably trivial and self contained.  Note the offb
  patches outside of arch/powerpc, they are LE fixes for our
  open-firmware 'dumb' framebuffer"

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc:
  powerpc: Fix up the kdump base cap to 128M
  powernv: Fix VFIO support with PHB3
  powerpc/52xx: Re-enable bestcomm driver in defconfigs
  powerpc/pasemi: Turn on devtmpfs in defconfig
  offb: Add palette hack for little endian
  offb: Little endian fixes
  powerpc: Fix PTE page address mismatch in pgtable ctor/dtor
  powerpc/44x: Fix ocm_block allocation
  powerpc: Fix build break with PPC_EARLY_DEBUG_BOOTX=y
  powerpc/512x: dts: remove misplaced IRQ spec from 'soc' node

The current logic sets the kdump base to min of 2G or ppc64_rma_size/2.
On PowerNV kernel the first memory block 'memory@0' can be very large,
equal to the DIMM size with ppc64_rma_size value capped to 1G. Hence on
PowerNV, kdump base is set to 512M resulting kdump to fail while allocating
paca array. This is because, paca need its memory from RMA region capped
at 256M (see allocate_pacas()).

This patch lowers the kdump base cap to 128M so that kdump kernel can
successfully get memory below 256M for paca allocation.
Signed-off-by: NMahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

I have recently found out that no iommu_groups could be found under
/sys/ on a P8. That prevents PCI passthrough from working.

During my investigation, I found out there seems to be a missing
iommu_register_group for PHB3. The following patch seems to fix the
problem. After applying it, I see iommu_groups under
/sys/kernel/iommu_groups/, and can also bind vfio-pci to an adapter,
which gives me a device at /dev/vfio/.
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The bestcomm driver has been moved to drivers/dma, so to select
this driver by default additionally CONFIG_DMADEVICES has to be
enabled. Currently it is not enabled in the config despite existing
CONFIG_PPC_BESTCOMM=y in the config files. Fix it.
Signed-off-by: NAnatolij Gustschin <agust@denx.de>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

At least some distros expect it these days; turn it on. Also, random
churn from doing a savedefconfig for the first time in a year or so.
Signed-off-by: NOlof Johansson <olof@lixom.net>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The pseudo palette color entries need to be ajusted for little
endian.

This patch byteswaps the values in the pseudo palette depending
on the host endian order and the screen depth.
Signed-off-by: NCédric Le Goater <clg@fr.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The "screen" properties : depth, width, height, linebytes need
to be converted to the host endian order when read from the device
tree.

The offb_init_palette_hacks() routine also made assumption on the
host endian order.
Signed-off-by: NCédric Le Goater <clg@fr.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

In pte_alloc_one(), pgtable_page_ctor() is passed an address that has
not been converted by page_address() to the newly allocated PTE page.

When the PTE is freed, __pte_free_tlb() calls pgtable_page_dtor()
with an address to the PTE page that has been converted by page_address().
The mismatch in the PTE's page address causes pgtable_page_dtor() to access
invalid memory, so resources for that PTE (such as the page lock) is not
properly cleaned up.

On PPC32, only SMP kernels are affected.

On PPC64, only SMP kernels with 4K page size are affected.

This bug was introduced by commit d614bb04
"powerpc: Move the pte free routines from common header".

On a preempt-rt kernel, a spinlock is dynamically allocated for each
PTE in pgtable_page_ctor().  When the PTE is freed, calling
pgtable_page_dtor() with a mismatched page address causes a memory leak,
as the pointer to the PTE's spinlock is bogus.

On mainline, there isn't any immediately obvious symptoms, but the
problem still exists here.

Fixes: d614bb04 "powerpc: Move the pte free routes from common header"
Cc: Paul Mackerras <paulus@samba.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linux-stable <stable@vger.kernel.org> # v3.10+
Signed-off-by: NHong H. Pham <hong.pham@windriver.com>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Allocate enough memory for the ocm_block structure, not just a pointer
to it.
Signed-off-by: NIlia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

A kernel configured with PPC_EARLY_DEBUG_BOOTX=y but PPC_PMAC=n and
PPC_MAPLE=n will fail to link:

  btext.c:(.text+0x2d0fc): undefined reference to `.rmci_off'
  btext.c:(.text+0x2d214): undefined reference to `.rmci_on'

Fix it by making the build of rmci_on/off() depend on
PPC_EARLY_DEBUG_BOOTX, which also enable the only code that uses them.
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Anatolij Gustschin says:

<<
Please pull a device tree fix for v3.13. The booting on mpc512x
is broken since v3.13-rc1, this patch repairs it.
>>

Pull drm fixes from Dave Airlie:
 "This is probably a bit big, but just because I fell behind last week
  and didn't get to doing any pulls, so stuff backed up behind me, I
  actually should have sent this for -rc3 but failed to even manage
  that.

  So this has radeon, intel, nouveau, vmware, exynos and tegra fixes in
  it, and the line count isn't all the bad in the end"

* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux: (50 commits)
  drm: fix the addition of the side-by-side (half) flag for extra 3D modes
  drm/edid: fix length check when adding extra 3D modes
  drm/radeon/atom: fix bus probes when hw_i2c is set (v2)
  drm/radeon: fix null pointer dereference in dce6+ audio code
  drm/radeon: fixup bad vram size on SI
  udl: fix issue with imported prime buffers
  drm/vmwgfx: Add our connectors to sysfs
  drm/vmwgfx: Fix dma buffer memory size accounting
  drm/vmwgfx: Fix up and comment the dumb buffer implementation
  drm/vmwgfx: Correctly set the enabled state on crtcs
  drm/nv50/disp: min/max are reversed in nv50_crtc_gamma_set()
  drm/nouveau/sw: fix oops if gpu has its display block disabled
  drm/nouveau: unreference fence after syncing
  drm/nouveau/kms: send timestamp data for correct head in flip completion events
  drm/nouveau/clk: Add support for NVAA/NVAC
  drm/nouveau/fifo: Hook up pause and resume for NV50 and NV84+
  drm/nv10/plane: some chipsets don't support NV12
  drm/nv10/plane: add downscaling restrictions
  drm/nv10/plane: fix format computation
  drm/nv04-nv30/clk: provide an empty domain list
  ...

Pull mfd fixes from Samuel Ortiz:
 "This is the first 3.13 pull request for MFD fixes.  We have:

   - A ti-ssp build failure fix
   - An as3722 build failure fix
   - An lpc_ich copy paste error fix"

* tag 'mfd-fixes-3.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/sameo/mfd-fixes:
  mfd: lpc_ich: Fix Wildcat Point info name field
  mfd: ti-ssp: Fix build
  mfd: Make MFD_AS3722 depend on I2C=y

Pull power management fixup from Rafael Wysocki:
 "This reverts two cpufreq commits that fixed issues for some people,
  but broke things for others, so revert them and we'll need to fix the
  original problems differently"

* tag 'pm-3.13-rc3-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  Revert "cpufreq: fix garbage kobjects on errors during suspend/resume"
  Revert "cpufreq: suspend governors on system suspend/hibernate"

Pull input updates from Dmitry Torokhov:
 "An update to ALPS to support devices on Dell XT2 (hopefully working
  better this time around and although it is largish it should not
  affect any other ALPS devices) and a tiny update to Elantech driver to
  support newer devices as well.

  Also a coupe of new input event codes have been defined"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: ALPS - add support for DualPoint device on Dell XT2 model
  Input: elantech - add support for newer (August 2013) devices
  Input: add SW_MUTE_DEVICE switch definition
  Input: usbtouchscreen - separate report and transmit buffer size handling
  Input: sur40 - suppress false uninitialized variable warning
  Input: add key code for ambient light sensor button
  Input: keyboard - "keycode & KEY_MAX" changes some keycode values

Pull crypto fix from Herbert Xu:
 "Unfortunately the last push that fixed a crash in the crypto
  scatterwalk code introduced a new crash when SG debugging is enabled.
  This fixes that"

* git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: scatterwalk - Use sg_chain_ptr on chain entries

Now that scatterwalk_sg_chain sets the chain pointer bit the sg_page
call in scatterwalk_sg_next hits a BUG_ON when CONFIG_DEBUG_SG is
enabled. Use sg_chain_ptr instead of sg_page on a chain entry.

Cc: stable@vger.kernel.org
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>