[Intel-gfx] [PATCH] drm/i915: Update ring space correctly on lrc context reset

[Mika Kuoppala]

If we leave the last_retired_head to pre-reset value, we might
end up in a situation where intel_ring_space() returns wrong
value on next hardware init.

The recent GuC changes made ringbuffer size much smaller. Thus
the odds grew that we got pre-reset last_retired_head in
a value so that intel_ring_space() returned too small value after
reset for mocs values to fit, triggering the following trace:

[  337.622311] ------------[ cut here ]------------
[  337.622362] WARNING: CPU: 0 PID: 1355 at drivers/gpu/drm/i915/intel_lrc.c:678 intel_logical_ring_begin+0x171/0x1dd [i915]()
[  337.622365] WARN_ON(&target->list == &ring->request_list)
[  337.622368] Modules linked in: snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy x86_pkg_temp_thermal coretemp kvm_intel snd_seq_oss kvm microcode snd_seq_midi asix joydev snd_rawmidi usbnet snd_seq_midi_event input_leds serio_raw snd_seq snd_seq_device snd_timer i915 snd soundcore drm_kms_helper shpchp syscopyarea sysfillrect sysimgblt fb_sys_fops drm wmi battery ipv6 bnep video bluetooth rfkill ac parport_pc button ppdev acpi_cpufreq lp parport sdhci_pci sdhci led_class mmc_core
[  337.622461] CPU: 0 PID: 1355 Comm: kworker/u16:2 Tainted: G     U  W       4.2.0-rc5-drm-intel-nightly-ww33+ #1
[  337.622465] Hardware name: Intel Corporation Skylake Client platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.X093.B02.1507222151 07/22/2015
[  337.622496] Workqueue: i915-hangcheck i915_hangcheck_elapsed [i915]
[  337.622500]  0000000000000009 ffff8800370838e8 ffffffff81897fb7 0000000000000000
[  337.622508]  ffff880037083938 ffff880037083928 ffffffff810467c3 ffff880037083908
[  337.622515]  ffffffffa02a6aea ffff8800873400c0 ffff88016d79e480 0000000000000000
[  337.622523] Call Trace:
[  337.622533]  [<ffffffff81897fb7>] dump_stack+0x45/0x57
[  337.622540]  [<ffffffff810467c3>] warn_slowpath_common+0xa1/0xbb
[  337.622584]  [<ffffffffa02a6aea>] ? intel_logical_ring_begin+0x171/0x1dd [i915]
[  337.622590]  [<ffffffff81046823>] warn_slowpath_fmt+0x46/0x48
[  337.622632]  [<ffffffffa02a6aea>] intel_logical_ring_begin+0x171/0x1dd [i915]
[  337.622674]  [<ffffffffa02a986d>] intel_rcs_context_init_mocs+0x170/0x2a9 [i915]
[  337.622714]  [<ffffffffa02a6ef5>] ? gen8_emit_flush_render+0x174/0x18f [i915]
[  337.622753]  [<ffffffffa02a77f0>] gen8_init_rcs_context+0x9d/0x1f9 [i915]
[  337.622792]  [<ffffffffa02a7248>] ? intel_logical_ring_reserve_space+0x26/0x2a [i915]
[  337.622827]  [<ffffffffa028ba91>] i915_gem_context_enable+0x26/0x4d [i915]
[  337.622866]  [<ffffffffa029a1b5>] i915_gem_init_hw+0x285/0x371 [i915]
[  337.622892]  [<ffffffffa0268a10>] i915_reset+0xe2/0x132 [i915]
[  337.622920]  [<ffffffffa026cd71>] i915_reset_and_wakeup+0xd3/0x133 [i915]
[  337.622948]  [<ffffffffa02709e2>] i915_handle_error+0x5ab/0x5bd [i915]
[  337.622956]  [<ffffffff810962bf>] ? vprintk_default+0x1d/0x1f
[  337.622962]  [<ffffffff8189398b>] ? printk+0x46/0x48
[  337.622990]  [<ffffffffa0270dbc>] i915_hangcheck_elapsed+0x387/0x3a7 [i915]
[  337.622996]  [<ffffffff8105c889>] process_one_work+0x225/0x409
[  337.623001]  [<ffffffff8105c80a>] ? process_one_work+0x1a6/0x409
[  337.623007]  [<ffffffff8105d2ce>] worker_thread+0x275/0x369
[  337.623013]  [<ffffffff8105d059>] ? cancel_delayed_work_sync+0x15/0x15
[  337.623019]  [<ffffffff81061ec8>] kthread+0xed/0xf5
[  337.623027]  [<ffffffff81061ddb>] ? kthread_create_on_node+0x1ac/0x1ac
[  337.623033]  [<ffffffff818a030f>] ret_from_fork+0x3f/0x70
[  337.623039]  [<ffffffff81061ddb>] ? kthread_create_on_node+0x1ac/0x1ac
[  337.623043] ---[ end trace bbf071dfdac9d9da ]---
[  337.623081] [drm:gen8_init_rcs_context [i915]] *ERROR* MOCS failed to program: expect performance issues.

Setup last_retired_head correctly on context reset and
recalculate free space for ringbuf.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91634
Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 60c683e..61c99e9 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2507,5 +2507,7 @@ void intel_lr_context_reset(struct drm_device *dev,
 
 		ringbuf->head = 0;
 		ringbuf->tail = 0;
+		ringbuf->last_retired_head = -1;
+		intel_ring_update_space(ringbuf);
 	}
 }
-- 
2.1.4