Quoting Maarten Lankhorst (2017-11-08 07:47:32)
> Op 07-11-17 om 22:47 schreef Chris Wilson:
> > During intel_atomic_check(), we do not take the intel_runtime_pm_get()
> > wakeref and so should do the atomic modeset precalculations without
> > referring to the HW. However, on Ironlake we see
> >
> > <7>[ 23.487557] [drm:intel_atomic_check [i915]] [CONNECTOR:47:VGA-1] checking for sink bpp constrains
> > <7>[ 23.487615] [drm:intel_atomic_check [i915]] clamping display bpp (was 36) to default limit of 24
> > <4>[ 23.487621] RPM wakelock ref not held during HW access
> > <4>[ 23.487652] ------------[ cut here ]------------
> > <4>[ 23.487697] WARNING: CPU: 0 PID: 1343 at drivers/gpu/drm/i915/intel_drv.h:1813 gen5_read32+0x183/0x200 [i915]
> > <4>[ 23.487701] Modules linked in: snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic i915 intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul snd_hda_intel ghash_clmulni_intel snd_hda_codec snd_hwdep snd_hda_core snd_pcm lpc_ich e1000e mei_me ptp mei pps_core prime_numbers
> > <4>[ 23.487784] CPU: 0 PID: 1343 Comm: debugfs_test Tainted: G W 4.14.0-rc7-CI-Trybot_1378+ #1
> > <4>[ 23.487788] Hardware name: Hewlett-Packard HP Compaq 8100 Elite SFF PC/304Ah, BIOS 786H1 v01.13 07/14/2011
> > <4>[ 23.487793] task: ffff8801f90aa6c0 task.stack: ffffc900013ec000
> > <4>[ 23.487838] RIP: 0010:gen5_read32+0x183/0x200 [i915]
> > <4>[ 23.487842] RSP: 0018:ffffc900013efb58 EFLAGS: 00010292
> > <4>[ 23.487849] RAX: 000000000000002a RBX: ffff880205c00000 RCX: 0000000000000006
> > <4>[ 23.487854] RDX: 000000000000140a RSI: ffffffff81d0eb14 RDI: ffffffff81cc26f6
> > <4>[ 23.487857] RBP: ffffc900013efb80 R08: ffff8801f90aaff8 R09: 0000000000000000
> > <4>[ 23.487861] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
> > <4>[ 23.487865] R13: 0000000000046000 R14: ffff88020ffaba78 R15: ffff88020b109bf8
> > <4>[ 23.487870] FS: 00007f53b5e40a40(0000) GS:ffff88021bc00000(0000) knlGS:0000000000000000
> > <4>[ 23.487874] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > <4>[ 23.487878] CR2: 000055e41900c0e8 CR3: 00000001fa0d6005 CR4: 00000000000206f0
> > <4>[ 23.487882] Call Trace:
> > <4>[ 23.487931] intel_atomic_check+0x745/0x1290 [i915]
> > <4>[ 23.487948] drm_atomic_check_only+0x459/0x560
> > <4>[ 23.487956] ? drm_atomic_set_crtc_for_connector+0xc9/0x100
> > <4>[ 23.488025] drm_atomic_commit+0x18/0x50
> > <4>[ 23.488035] restore_fbdev_mode_atomic+0x190/0x1f0
> > <4>[ 23.488059] restore_fbdev_mode+0x32/0x120
> > <4>[ 23.488072] drm_fb_helper_restore_fbdev_mode_unlocked+0x50/0xa0
> > <4>[ 23.488139] intel_fbdev_restore_mode+0x34/0x90 [i915]
> > <4>[ 23.488194] i915_driver_lastclose+0xe/0x10 [i915]
> > <4>[ 23.488208] drm_lastclose+0x39/0xf0
> > <4>[ 23.488219] drm_release+0x30c/0x3c0
> > <4>[ 23.488236] __fput+0xb9/0x200
> > <4>[ 23.488252] ____fput+0xe/0x10
> > <4>[ 23.488264] task_work_run+0x89/0xc0
> > <4>[ 23.488278] exit_to_usermode_loop+0x83/0x90
> > <4>[ 23.488290] syscall_return_slowpath+0xd0/0x110
> > <4>[ 23.488304] entry_SYSCALL_64_fastpath+0xaf/0xb1
> > <4>[ 23.488312] RIP: 0033:0x7f53b4317560
> > <4>[ 23.488320] RSP: 002b:00007ffca7e70748 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
> > <4>[ 23.488333] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 00007f53b4317560
> > <4>[ 23.488340] RDX: 0000000000000005 RSI: 00007ffca7e70640 RDI: 0000000000000004
> > <4>[ 23.488347] RBP: 000055e417783900 R08: 000055e418f9e290 R09: 0000000000000000
> > <4>[ 23.488356] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> > <4>[ 23.488363] R13: 00007f53b4302c40 R14: 0000000000000000 R15: 0000000000000000
> > <4>[ 23.488384] Code: b5 f2 f2 e0 0f ff e9 c5 fe ff ff 80 3d 0e 4b 10 00 00 0f 85 c6 fe ff ff 48 c7 c7 30 73 29 a0 c6 05 fa 4a 10 00 01 e8 8e f2 f2 e0 <0f> ff e9 ac fe ff ff e8 51 9d f3 e0 85 c0 0f 85 01 ff ff ff 48
> > <4>[ 23.488780] ---[ end trace 6bc72ce7f1596190 ]---
> > <7>[ 23.488844] [drm:intel_atomic_check [i915]] checking fdi config on pipe A, lanes 1
> > <7>[ 23.488911] [drm:intel_atomic_check [i915]] hw max bpp: 36, pipe bpp: 24, dithering: 0
> >
> > due to intel_fdi_link_freq() poking at FDI_PLL_BIOS_0. Avoid this by
> > recording the fdi pll frequency during device initiailisation.
> >
> > v2: Also extract the static FDI PLL frequencies for Sandybridge and
> > Ivybridge.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_drv.h | 1 +
> > drivers/gpu/drm/i915/intel_display.c | 21 ++++++++++++++++++---
> > 2 files changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index fe93115c4caa..5e6938d0a903 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -2349,6 +2349,7 @@ struct drm_i915_private {
> > unsigned int max_dotclk_freq;
> > unsigned int rawclk_freq;
> > unsigned int hpll_freq;
> > + unsigned int fdi_pll_freq;
> > unsigned int czclk_freq;
> >
> > struct {
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 737de251d0f8..9331c62dcc7d 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -219,10 +219,8 @@ intel_fdi_link_freq(struct drm_i915_private *dev_priv,
> > {
> > if (HAS_DDI(dev_priv))
> > return pipe_config->port_clock; /* SPLL */
> > - else if (IS_GEN5(dev_priv))
> > - return ((I915_READ(FDI_PLL_BIOS_0) & FDI_PLL_FB_CLOCK_MASK) + 2) * 10000;
> > else
> > - return 270000;
> > + return dev_priv->fdi_pll_freq;
> > }
> >
> > static const struct intel_limit intel_limits_i8xx_dac = {
> > @@ -14454,6 +14452,22 @@ static void sanitize_watermarks(struct drm_device *dev)
> > drm_modeset_acquire_fini(&ctx);
> > }
> >
> > +static void intel_update_fdi_ppl_freq(struct drm_i915_private *dev_priv)
> > +{
> > + if (IS_GEN5(dev_priv)) {
> > + u32 fdi_pll_clk =
> > + I915_READ(FDI_PLL_BIOS_0) & FDI_PLL_FB_CLOCK_MASK;
> > +
> > + dev_priv->fdi_pll_freq = (fdi_pll_clk + 2) * 10000;
> > + } else if (IS_GEN6(dev_priv) || IS_IVYBRIDGE(dev_priv)) {
> > + dev_priv->fdi_pll_freq = 270000;
> > + } else {
> > + return;
> > + }
> > +
> > + DRM_DEBUG_DRIVER("FDI PLL freq=%d\n", dev_priv->fdi_pll_freq);
> > +}
> > +
> > int intel_modeset_init(struct drm_device *dev)
> > {
> > struct drm_i915_private *dev_priv = to_i915(dev);
> > @@ -14541,6 +14555,7 @@ int intel_modeset_init(struct drm_device *dev)
> > }
> >
> > intel_shared_dpll_init(dev);
> > + intel_update_fdi_ppl_freq(dev_priv);
> >
> > intel_update_czclk(dev_priv);
> > intel_modeset_init_hw(dev);
>
> Is there any testcase that hits this? Would be nice to prevent future occurences, since there are so many potential places we hit this. But yeah atomic_check needs to be careful about mmio access during atomic_check().
CI caught it in debugfs_test/read_all (or whatever that first is called).
All it takes is for us to remove the early multi-second rpm wakeref we hold
to expose it. After that I'm not sure why we don't see it more often
during igt; my guess is that the 100ms wakeref from gem_quiescent_gpu()
is hiding a lot.
-Chris
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