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  1. 25 11月, 2015 1 次提交
  3. 24 11月, 2015 3 次提交
  5. 19 11月, 2015 1 次提交
  7. 18 11月, 2015 2 次提交
  9. 17 11月, 2015 2 次提交
    • V
      drm/i915: Don't clobber the addfb2 ioctl params · 76dc3769
      由 Ville Syrjälä 提交于 
      We try to convert the old way of of specifying fb tiling (obj->tiling)
into the new fb modifiers. We store the result in the passed in mode_cmd
structure. But that structure comes directly from the addfb2 ioctl, and
gets copied back out to userspace, which means we're clobbering the
modifiers that the user provided (all 0 since the DRM_MODE_FB_MODIFIERS
flag wasn't even set by the user). Hence if the user reuses the struct
for another addfb2, the ioctl will be rejected since it's now asking for
some modifiers w/o the flag set.

Fix the problem by making a copy of the user provided structure. We can
play any games we want with the copy.

IGT-Version: 1.12-git (x86_64) (Linux: 4.4.0-rc1-stereo+ x86_64)
...
Subtest basic-X-tiled: SUCCESS (0.001s)
Test assertion failure function pitch_tests, file kms_addfb_basic.c:167:
Failed assertion: drmIoctl(fd, DRM_IOCTL_MODE_ADDFB2, &f) == 0
Last errno: 22, Invalid argument
Stack trace:
  #0 [__igt_fail_assert+0x101]
  #1 [pitch_tests+0x619]
  #2 [__real_main426+0x2f]
  #3 [main+0x23]
  #4 [__libc_start_main+0xf0]
  #5 [_start+0x29]
  #6 [<unknown>+0x29]
  Subtest framebuffer-vs-set-tiling failed.
  **** DEBUG ****
  Test assertion failure function pitch_tests, file kms_addfb_basic.c:167:
  Failed assertion: drmIoctl(fd, DRM_IOCTL_MODE_ADDFB2, &f) == 0
  Last errno: 22, Invalid argument
  ****  END  ****
  Subtest framebuffer-vs-set-tiling: FAIL (0.003s)
  ...

IGT-Version: 1.12-git (x86_64) (Linux: 4.4.0-rc1-stereo+ x86_64)
Subtest framebuffer-vs-set-tiling: SUCCESS (0.000s)

Cc: stable@vger.kernel.org # v4.1+
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 2a80eada ("drm/i915: Add fb format modifier support")
Testcase: igt/kms_addfb_basic/clobbered-modifier
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1447261890-3960-1-git-send-email-ville.syrjala@linux.intel.com
      76dc3769
    • M
      drm/i915: Clear intel_crtc->atomic before updating it. · ba8af3e5
      由 Maarten Lankhorst 提交于 
      If an atomic update fails intel_crtc->atomic may have have some values left
from the last atomic check. One example is atomic->wait_for_vblank,
which results in spurious errors in kms_flip.

[ 1551.892708] ------------[ cut here ]------------
[ 1551.892721] WARNING: CPU: 3 PID: 4179 at ../drivers/gpu/drm/drm_irq.c:1199 drm_wait_one_vblank+0x197/0x1a0 [drm]()
[ 1551.892722] vblank not available on crtc 2, ret=-22
[ 1551.892751] Modules linked in: snd_hda_intel i915 drm_kms_helper drm
intel_gtt i2c_algo_bit cfbfillrect syscopyarea cfbimgblt sysfillrect
sysimgblt fb_sys_fops cfbcopyarea agpgart cfg80211 binfmt_misc
snd_hda_codec_hdmi intel_rapl iosf_mbi x86_pkg_temp_thermal coretemp
kvm_intel snd_hda_codec_realtek kvm snd_hda_codec_generic iTCO_wdt
aesni_intel aes_x86_64 glue_helper lrw snd_hda_codec gf128mul
ablk_helper cryptd snd_hwdep psmouse snd_hda_core pcspkr snd_pcm
snd_timer snd lpc_ich i2c_i801 mfd_core soundcore wmi evdev [last
unloaded: drm]
[ 1551.892753] CPU: 3 PID: 4179 Comm: kms_pipe_crc_ba Tainted: G     U  W       4.3.0-reg+ #6
[ 1551.892754] Hardware name:                  /DZ77BH-55K, BIOS BHZ7710H.86A.0100.2013.0517.0942 05/17/2013
[ 1551.892758]  ffffffffa03128d8 ffff8800cec73890 ffffffff812c0f3c ffff8800cec738d8
[ 1551.892760]  ffff8800cec738c8 ffffffff8104ff36 ffff880116ae2290 0000000000000002
[ 1551.892762]  ffff8800d39fcda0 ffff8800d038b4d0 ffff8800d42b5550 ffff8800cec73928
[ 1551.892763] Call Trace:
[ 1551.892768]  [<ffffffff812c0f3c>] dump_stack+0x4e/0x82
[ 1551.892771]  [<ffffffff8104ff36>] warn_slowpath_common+0x86/0xc0
[ 1551.892773]  [<ffffffff8104ffbc>] warn_slowpath_fmt+0x4c/0x50
[ 1551.892781]  [<ffffffffa02e6708>] ? drm_vblank_get+0x78/0xd0 [drm]
[ 1551.892787]  [<ffffffffa02e6d47>] drm_wait_one_vblank+0x197/0x1a0 [drm]
[ 1551.892813]  [<ffffffffa03d052f>] intel_post_plane_update+0xef/0x120 [i915]
[ 1551.892832]  [<ffffffffa03d11d2>] intel_atomic_commit+0x4c2/0x1600 [i915]
[ 1551.892862]  [<ffffffffa02ff0c7>] ? drm_atomic_check_only+0x147/0x5e0 [drm]
[ 1551.892872]  [<ffffffffa02feeb7>] ? drm_atomic_add_affected_connectors+0x27/0xf0 [drm]
[ 1551.892881]  [<ffffffffa02ff597>] drm_atomic_commit+0x37/0x60 [drm]
[ 1551.892887]  [<ffffffffa034301a>] restore_fbdev_mode+0x28a/0x2c0 [drm_kms_helper]
[ 1551.892895]  [<ffffffffa0345253>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
[ 1551.892900]  [<ffffffffa03452cd>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
[ 1551.892920]  [<ffffffffa03e7a9a>] intel_fbdev_set_par+0x1a/0x60 [i915]
[ 1551.892923]  [<ffffffff8131a5a7>] fb_set_var+0x1a7/0x3f0
[ 1551.892927]  [<ffffffff8109732f>] ? trace_hardirqs_on_caller+0x12f/0x1c0
[ 1551.892931]  [<ffffffff81314f32>] fbcon_blank+0x212/0x2f0
[ 1551.892935]  [<ffffffff81373f4a>] do_unblank_screen+0xba/0x1d0
[ 1551.892937]  [<ffffffff8136b725>] vt_ioctl+0x13d5/0x1450
[ 1551.892940]  [<ffffffff8107cdd1>] ? preempt_count_sub+0x41/0x50
[ 1551.892943]  [<ffffffff8135d8a3>] tty_ioctl+0x423/0xe30
[ 1551.892947]  [<ffffffff8119f721>] do_vfs_ioctl+0x301/0x560
[ 1551.892949]  [<ffffffff8119b1e3>] ? putname+0x53/0x60
[ 1551.892952]  [<ffffffff811ab376>] ? __fget_light+0x66/0x90
[ 1551.892955]  [<ffffffff8119f9f9>] SyS_ioctl+0x79/0x90
[ 1551.892958]  [<ffffffff81552e97>] entry_SYSCALL_64_fastpath+0x12/0x6f
[ 1551.892961] ---[ end trace 3e764d4b6628c91c ]---

Testcase: kms_flip
Reported-and-tested-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org #v4.3
Signed-off-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: NDaniel Stone <daniels@collabora.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/5649C2BA.6080300@mblankhorst.nl
      ba8af3e5
  11. 16 11月, 2015 4 次提交
  13. 07 11月, 2015 3 次提交
    • M
      mm, fs: introduce mapping_gfp_constraint() · c62d2555
      由 Michal Hocko 提交于 
      There are many places which use mapping_gfp_mask to restrict a more
generic gfp mask which would be used for allocations which are not
directly related to the page cache but they are performed in the same
context.

Let's introduce a helper function which makes the restriction explicit and
easier to track.  This patch doesn't introduce any functional changes.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c62d2555
    • M
      mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM · 71baba4b
      由 Mel Gorman 提交于 
      __GFP_WAIT was used to signal that the caller was in atomic context and
could not sleep.  Now it is possible to distinguish between true atomic
context and callers that are not willing to sleep.  The latter should
clear __GFP_DIRECT_RECLAIM so kswapd will still wake.  As clearing
__GFP_WAIT behaves differently, there is a risk that people will clear the
wrong flags.  This patch renames __GFP_WAIT to __GFP_RECLAIM to clearly
indicate what it does -- setting it allows all reclaim activity, clearing
them prevents it.

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      71baba4b
    • M
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep... · d0164adc
      由 Mel Gorman 提交于 
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd

__GFP_WAIT has been used to identify atomic context in callers that hold
spinlocks or are in interrupts.  They are expected to be high priority and
have access one of two watermarks lower than "min" which can be referred
to as the "atomic reserve".  __GFP_HIGH users get access to the first
lower watermark and can be called the "high priority reserve".

Over time, callers had a requirement to not block when fallback options
were available.  Some have abused __GFP_WAIT leading to a situation where
an optimisitic allocation with a fallback option can access atomic
reserves.

This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
cannot sleep and have no alternative.  High priority users continue to use
__GFP_HIGH.  __GFP_DIRECT_RECLAIM identifies callers that can sleep and
are willing to enter direct reclaim.  __GFP_KSWAPD_RECLAIM to identify
callers that want to wake kswapd for background reclaim.  __GFP_WAIT is
redefined as a caller that is willing to enter direct reclaim and wake
kswapd for background reclaim.

This patch then converts a number of sites

o __GFP_ATOMIC is used by callers that are high priority and have memory
  pools for those requests. GFP_ATOMIC uses this flag.

o Callers that have a limited mempool to guarantee forward progress clear
  __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
  into this category where kswapd will still be woken but atomic reserves
  are not used as there is a one-entry mempool to guarantee progress.

o Callers that are checking if they are non-blocking should use the
  helper gfpflags_allow_blocking() where possible. This is because
  checking for __GFP_WAIT as was done historically now can trigger false
  positives. Some exceptions like dm-crypt.c exist where the code intent
  is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
  flag manipulations.

o Callers that built their own GFP flags instead of starting with GFP_KERNEL
  and friends now also need to specify __GFP_KSWAPD_RECLAIM.

The first key hazard to watch out for is callers that removed __GFP_WAIT
and was depending on access to atomic reserves for inconspicuous reasons.
In some cases it may be appropriate for them to use __GFP_HIGH.

The second key hazard is callers that assembled their own combination of
GFP flags instead of starting with something like GFP_KERNEL.  They may
now wish to specify __GFP_KSWAPD_RECLAIM.  It's almost certainly harmless
if it's missed in most cases as other activity will wake kswapd.
Signed-off-by: NMel Gorman <mgorman@techsingularity.net>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d0164adc
  15. 06 11月, 2015 2 次提交
  17. 05 11月, 2015 2 次提交
  19. 04 11月, 2015 1 次提交
    • D
      drm/i915: Fix locking around GuC firmware load · bf248ca1
      由 Daniel Stone 提交于 
      The GuC firmware load requires struct_mutex to create a GEM object,
but this collides badly with request_firmware. Move struct_mutex
locking down into the loader itself, so we don't hold it across the
entire load process, including request_firmware.

[   20.451400] ======================================================
[   20.451420] [ INFO: possible circular locking dependency detected ]
[   20.451441] 4.3.0-rc5+ #1 Tainted: G        W
[   20.451457] -------------------------------------------------------
[   20.451477] plymouthd/371 is trying to acquire lock:
[   20.451494]  (&dev->struct_mutex){+.+.+.}, at: [<ffffffffa0093c62>]
drm_gem_mmap+0x112/0x290 [drm]
[   20.451538]
               but task is already holding lock:
[   20.451557]  (&mm->mmap_sem){++++++}, at: [<ffffffff811fd9ac>]
vm_mmap_pgoff+0x8c/0xf0
[   20.451591]
               which lock already depends on the new lock.

[   20.451617]
               the existing dependency chain (in reverse order) is:
[   20.451640]
               -> #3 (&mm->mmap_sem){++++++}:
[   20.451661]        [<ffffffff8110644e>] lock_acquire+0xce/0x1c0
[   20.451683]        [<ffffffff8120ec9a>] __might_fault+0x7a/0xa0
[   20.451705]        [<ffffffff8127e34e>] filldir+0x9e/0x130
[   20.451726]        [<ffffffff81295b86>] dcache_readdir+0x186/0x230
[   20.451748]        [<ffffffff8127e117>] iterate_dir+0x97/0x130
[   20.451769]        [<ffffffff8127e66a>] SyS_getdents+0x9a/0x130
[   20.451790]        [<ffffffff8184f2f2>] entry_SYSCALL_64_fastpath+0x12/0x76
[   20.451829]
               -> #2 (&sb->s_type->i_mutex_key#2){+.+.+.}:
[   20.451852]        [<ffffffff8110644e>] lock_acquire+0xce/0x1c0
[   20.451872]        [<ffffffff8184b516>] mutex_lock_nested+0x86/0x400
[   20.451893]        [<ffffffff81277790>] walk_component+0x1d0/0x2a0
[   20.451914]        [<ffffffff812779f0>] link_path_walk+0x190/0x5a0
[   20.451935]        [<ffffffff8127803b>] path_openat+0xab/0x1260
[   20.451955]        [<ffffffff8127a651>] do_filp_open+0x91/0x100
[   20.451975]        [<ffffffff81267e67>] file_open_name+0xf7/0x150
[   20.451995]        [<ffffffff81267ef3>] filp_open+0x33/0x60
[   20.452014]        [<ffffffff8157e1e7>] _request_firmware+0x277/0x880
[   20.452038]        [<ffffffff8157e9e4>] request_firmware_work_func+0x34/0x80
[   20.452060]        [<ffffffff810c7020>] process_one_work+0x230/0x680
[   20.452082]        [<ffffffff810c74be>] worker_thread+0x4e/0x450
[   20.452102]        [<ffffffff810ce511>] kthread+0x101/0x120
[   20.452121]        [<ffffffff8184f66f>] ret_from_fork+0x3f/0x70
[   20.452140]
               -> #1 (umhelper_sem){++++.+}:
[   20.452159]        [<ffffffff8110644e>] lock_acquire+0xce/0x1c0
[   20.452178]        [<ffffffff8184c5c1>] down_read+0x51/0xa0
[   20.452197]        [<ffffffff810c203b>]
usermodehelper_read_trylock+0x5b/0x130
[   20.452221]        [<ffffffff8157e147>] _request_firmware+0x1d7/0x880
[   20.452242]        [<ffffffff8157e821>] request_firmware+0x31/0x50
[   20.452262]        [<ffffffffa01b54a4>]
intel_guc_ucode_init+0xf4/0x400 [i915]
[   20.452305]        [<ffffffffa0213913>] i915_driver_load+0xd63/0x16e0 [i915]
[   20.452343]        [<ffffffffa00987d9>] drm_dev_register+0xa9/0xc0 [drm]
[   20.452369]        [<ffffffffa009ae3d>] drm_get_pci_dev+0x8d/0x1e0 [drm]
[   20.452396]        [<ffffffffa01521e4>] i915_pci_probe+0x34/0x50 [i915]
[   20.452421]        [<ffffffff81464675>] local_pci_probe+0x45/0xa0
[   20.452443]        [<ffffffff81465a6d>] pci_device_probe+0xfd/0x140
[   20.452464]        [<ffffffff8156a2e4>] driver_probe_device+0x224/0x480
[   20.452486]        [<ffffffff8156a5c8>] __driver_attach+0x88/0x90
[   20.452505]        [<ffffffff81567cf3>] bus_for_each_dev+0x73/0xc0
[   20.452526]        [<ffffffff81569a7e>] driver_attach+0x1e/0x20
[   20.452546]        [<ffffffff815695ae>] bus_add_driver+0x1ee/0x280
[   20.452566]        [<ffffffff8156b100>] driver_register+0x60/0xe0
[   20.453197]        [<ffffffff81464050>] __pci_register_driver+0x60/0x70
[   20.453845]        [<ffffffffa009b070>] drm_pci_init+0xe0/0x110 [drm]
[   20.454497]        [<ffffffffa027f092>] 0xffffffffa027f092
[   20.455156]        [<ffffffff81002123>] do_one_initcall+0xb3/0x200
[   20.455796]        [<ffffffff811d8c01>] do_init_module+0x5f/0x1e7
[   20.456434]        [<ffffffff8114c4e6>] load_module+0x2126/0x27d0
[   20.457071]        [<ffffffff8114cdf9>] SyS_finit_module+0xb9/0xf0
[   20.457738]        [<ffffffff8184f2f2>] entry_SYSCALL_64_fastpath+0x12/0x76
[   20.458370]
               -> #0 (&dev->struct_mutex){+.+.+.}:
[   20.459773]        [<ffffffff8110584f>] __lock_acquire+0x191f/0x1ba0
[   20.460451]        [<ffffffff8110644e>] lock_acquire+0xce/0x1c0
[   20.461074]        [<ffffffffa0093c88>] drm_gem_mmap+0x138/0x290 [drm]
[   20.461693]        [<ffffffff8121a5ec>] mmap_region+0x3ec/0x670
[   20.462298]        [<ffffffff8121abb2>] do_mmap+0x342/0x420
[   20.462901]        [<ffffffff811fd9d2>] vm_mmap_pgoff+0xb2/0xf0
[   20.463532]        [<ffffffff81218f62>] SyS_mmap_pgoff+0x1f2/0x290
[   20.464118]        [<ffffffff8102187b>] SyS_mmap+0x1b/0x30
[   20.464702]        [<ffffffff8184f2f2>] entry_SYSCALL_64_fastpath+0x12/0x76
[   20.465289]
               other info that might help us debug this:

[   20.467179] Chain exists of:
                 &dev->struct_mutex --> &sb->s_type->i_mutex_key#2 -->
&mm->mmap_sem

[   20.468928]  Possible unsafe locking scenario:

[   20.470161]        CPU0                    CPU1
[   20.470745]        ----                    ----
[   20.471325]   lock(&mm->mmap_sem);
[   20.471902]                                lock(&sb->s_type->i_mutex_key#2);
[   20.472538]                                lock(&mm->mmap_sem);
[   20.473118]   lock(&dev->struct_mutex);
[   20.473704]
                *** DEADLOCK ***
Signed-off-by: NDaniel Stone <daniels@collabora.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>
      bf248ca1
  21. 02 11月, 2015 2 次提交
  23. 29 10月, 2015 1 次提交
  25. 27 10月, 2015 1 次提交
  27. 22 10月, 2015 1 次提交
  29. 19 10月, 2015 1 次提交
  31. 16 10月, 2015 3 次提交
  33. 15 10月, 2015 3 次提交
  35. 14 10月, 2015 4 次提交
  37. 13 10月, 2015 3 次提交
    • M
      drm/i915: Move skl/bxt gt specific workarounds to ring init · 9c4cbf82
      由 Mika Kuoppala 提交于 
      Some registers are, naturally, lost in gpu reset/suspend cycle.
And some registers, for example in display domain, are not subject
to gpu reset so they retain their contents.

As hang recovery triggers a reset, recoverable gpu hang can currently
flush out essential workarounds and cause havoc later on.

When register GEN8_GARBNTL is missing the WaEnableGapsTsvCreditFix:skl,
it can cause random system hangs [1]. This workaround was added in:
commit 245d9667 ("drm/i915:skl: Add WaEnableGapsTsvCreditFix")
But another set of system hangs were observed and the failure pattern
indicated that there was random gpu hang preceding the system hang [2].
This lead to the realization that we lose this workaround and BDW_SCRATCH1
on reset.

Add these workarounds setup in display init to skl/bxt ring init
where LRI workarounds are also setup. This way their setup is not
dependent on display side init.

References: [1] https://bugs.freedesktop.org/show_bug.cgi?id=90854
References: [2] https://bugs.freedesktop.org/show_bug.cgi?id=92315Reported-by: NTomi Sarvela <tomix.p.sarvela@intel.com>
Cc: Tomi Sarvela <tomix.p.sarvela@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Tested-by: NTomi Sarvela <tomix.p.sarvela@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      9c4cbf82
    • C
      drm/i915: Deny wrapping an userptr into a framebuffer · cc917ab4
      由 Chris Wilson 提交于 
      Pinning a userptr onto the hardware raises interesting questions about
the lifetime of such a surface as the framebuffer extends that life
beyond the client's address space. That is the hardware will need to
keep scanning out from the backing storage even after the client wants
to remap its address space. As the hardware pins the backing storage,
the userptr becomes invalid and this raises a WARN when the clients
tries to unmap its address space. The situation can be even more
complicated when the buffer is passed between processes, between a
client and display server, where the lifetime and hardware access is
even more confusing. Deny it.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
      cc917ab4
    • V
      drm/i915: Enable DPLL VGA mode before P1/P2 divider write · c2b63374
      由 Ville Syrjälä 提交于 
      Apparently writing the DPLL register P1/P2 divider fields won't trigger
an actual change in the DPLL output unless VGA mode is enabled for
prior to the register write that changes the P1/P2 dividers. The write
with the new P1/P2 divider can itself disable VGA mode again without
problems.

I tested the behaviour on my 946GZ, and when manually frobbing the
register with the display on, the behaviour is very clear. However I
can't explain why this machine actually works. The P1/P2 divider
changes caused by normal modesets do seem to make it through to the
hardware somehow since I get a stable picture on the monitor with
any resolution. Maybe it's the "three times for luck" stuff that
somehow masks the problem, or something.

But apparently there are machines (eg. Nick Bowler's G45) where that
isn't the case and we fail to get the correct clock from the DPLL.

Things used to work because we enabled VGA mode for disabled DPLLs,
so when re-enabling the DPLL VGA mode was enabled just prior to the
first register write, and hence the P1/P2 change went through without
a hitch. That got changed in

b8afb911 drm/i915: Keep GMCH DPLL VGA mode always disabled

in the name of consistency. In order to keep the consistency part,
leave VGA mode disabled for disabled DPLLs, but turn it on just prior
to updating the P1/P2 dividers to make sure the hardware picks up
on the new values.

Cc: Nick Bowler <nbowler@draconx.ca>
Reported-by: NNick Bowler <nbowler@draconx.ca>
Tested-by: NNick Bowler <nbowler@draconx.ca>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
      c2b63374