On Wed, Feb 17, 2016 at 5:36 PM, Andy Lutomirski <[email protected]> wrote:
> On Wed, Feb 17, 2016 at 8:18 AM, Daniel Vetter <[email protected]> wrote:
>> On Tue, Feb 16, 2016 at 09:26:35AM -0800, Andy Lutomirski wrote:
>>> On Tue, Feb 16, 2016 at 9:12 AM, Andy Lutomirski <[email protected]>
>>> wrote:
>>> > On Tue, Feb 16, 2016 at 8:12 AM, Daniel Vetter <[email protected]> wrote:
>>> >> On Mon, Feb 15, 2016 at 06:58:33AM -0800, Andy Lutomirski wrote:
>>> >>> On Sun, Feb 14, 2016 at 6:59 PM, Andy Lutomirski <[email protected]>
>>> >>> wrote:
>>> >>> > Hi-
>>> >>> >
>>> >>> > On 4.5-rc3 on a Dell XPS 13 9350 (Skylake i915, no nvidia on this
>>> >>> > model), shortly after resume, I saw a single black flash on the
>>> >>> > screen. The log said:
>>> >>> >
>>> >>> > [Feb13 07:05] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR*
>>> >>> > CPU pipe A FIFO underrun
>>> >>> >
>>> >>> > I haven't seen this on 4.4.
>>> >>> >
>>> >>> > I'd be happy to dig up debugging info, but I don't know what would be
>>> >>> > useful. I have no i915 module options set.
>>> >>>
>>> >>> It's flashing quite frequently now, although I seem to get the
>>> >>> underrun warning only once per resume.
>>> >>
>>> >> We shut up the warning irq source to avoid hijacking an entire cpu core
>>> >> ;-)
>>> >>
>>> >> There's a fix from Matt right after 4.5-rc4 in Linus' branch. I'm hoping
>>> >> that should help.
>>> >
>>> > Do you mean:
>>> >
>>> > commit e2e407dc093f530b771ee8bf8fe1be41e3cea8b3
>>> > Author: Matt Roper <[email protected]>
>>> > Date: Mon Feb 8 11:05:28 2016 -0800
>>> >
>>> > drm/i915: Pretend cursor is always on for ILK-style WM calculations
>>> > (v2)
>>> >
>>> > If so, it didn't help. I'm currently doing a full rebuild just in
>>> > case I messed something up, though.
>>> >
>>>
>>> Definitely not fixed. It seems to be okay after a reboot until the
>>> first suspend/resume.
>>>
>>> This happened after resuming. Five cents says it's the root cause.
>>
>> That's interesting, but doesn't ring a bell unfortunately. Can you try to
>> attempt a bisect?
>
> I probably can, but it's very slow. Is there a reasonably
> straightforward way to instrument the watermark computation to see
> what's going wrong? I'm reasonably confident that the bug is in the
> resume code or in something that only happens on resume, since I still
> haven't seen underruns after rebooting before suspending.
>
With some instrumentation applied, I got this:
[ 369.471064] skl_update_wm(crtc-0): computed update
[ 369.471072] skl_update_other_pipe_wm(crtc-0): no change
[ 369.471075] skl_write_wm_values...
[ 369.471078] CRTC crtc-0 pipe A
[ 369.471083] wm_linetime = 121
[ 369.471086] plane_wm level 0 plane 0 = 2147500036
[ 369.471090] plane_wm level 0 plane 1 = 0
[ 369.471094] plane_wm level 0 cursor = 2147500036
[ 369.471097] plane_wm level 1 plane 0 = 2147516439
[ 369.471101] plane_wm level 1 plane 1 = 0
[ 369.471104] plane_wm level 1 cursor = 2147516439
[ 369.471108] plane_wm level 2 plane 0 = 2147516448
[ 369.471111] plane_wm level 2 plane 1 = 0
[ 369.471115] plane_wm level 2 cursor = 0
[ 369.471118] plane_wm level 3 plane 0 = 2147532837
[ 369.471121] plane_wm level 3 plane 1 = 0
[ 369.471125] plane_wm level 3 cursor = 0
[ 369.471128] plane_wm level 4 plane 0 = 2147565639
[ 369.471131] plane_wm level 4 plane 1 = 0
[ 369.471135] plane_wm level 4 cursor = 0
[ 369.471138] plane_wm level 5 plane 0 = 2147582038
[ 369.471141] plane_wm level 5 plane 1 = 0
[ 369.471145] plane_wm level 5 cursor = 0
[ 369.471148] plane_wm level 6 plane 0 = 2147582044
[ 369.471151] plane_wm level 6 plane 1 = 0
[ 369.471155] plane_wm level 6 cursor = 0
[ 369.471158] plane_wm level 7 plane 0 = 2147598443
[ 369.471161] plane_wm level 7 plane 1 = 0
[ 369.471164] plane_wm level 7 cursor = 0
[ 369.471168] wm_trans plane 0 = 0
[ 369.471171] wm_trans plane 1 = 0
[ 369.471174] wm_trans cursor = 0
[ 369.471182] CRTC crtc-1 pipe B
[ 369.471184] clean
[ 369.471186] CRTC crtc-2 pipe C
[ 369.471189] clean
[ 369.471226] skl_update_wm(crtc-0): no update
[ 372.068755] [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
*ERROR* CPU pipe A FIFO underrun
[ 373.399396] skl_update_wm(crtc-0): computed update
[ 373.399408] skl_update_other_pipe_wm(crtc-0): no change
[ 373.399413] skl_write_wm_values...
[ 373.399418] CRTC crtc-0 pipe A
[ 373.399426] wm_linetime = 121
[ 373.399431] plane_wm level 0 plane 0 = 2147500036
[ 373.399438] plane_wm level 0 plane 1 = 0
[ 373.399443] plane_wm level 0 cursor = 16388
[ 373.399449] plane_wm level 1 plane 0 = 2147516439
[ 373.399455] plane_wm level 1 plane 1 = 0
[ 373.399460] plane_wm level 1 cursor = 32791
[ 373.399465] plane_wm level 2 plane 0 = 2147516448
[ 373.399471] plane_wm level 2 plane 1 = 0
[ 373.399476] plane_wm level 2 cursor = 0
[ 373.399481] plane_wm level 3 plane 0 = 2147532837
[ 373.399486] plane_wm level 3 plane 1 = 0
[ 373.399491] plane_wm level 3 cursor = 0
[ 373.399497] plane_wm level 4 plane 0 = 2147565639
[ 373.399502] plane_wm level 4 plane 1 = 0
[ 373.399557] plane_wm level 4 cursor = 0
[ 373.399562] plane_wm level 5 plane 0 = 2147582038
[ 373.399568] plane_wm level 5 plane 1 = 0
[ 373.399573] plane_wm level 5 cursor = 0
[ 373.399578] plane_wm level 6 plane 0 = 2147582044
[ 373.399591] plane_wm level 6 plane 1 = 0
[ 373.399596] plane_wm level 6 cursor = 0
[ 373.399602] plane_wm level 7 plane 0 = 2147598443
[ 373.399607] plane_wm level 7 plane 1 = 0
[ 373.399612] plane_wm level 7 cursor = 0
[ 373.399617] wm_trans plane 0 = 0
[ 373.399623] wm_trans plane 1 = 0
[ 373.399627] wm_trans cursor = 0
[ 373.399638] CRTC crtc-1 pipe B
[ 373.399642] clean
[ 373.399646] CRTC crtc-2 pipe C
[ 373.399650] clean
The diff between those two dumps was:
--- a.txt 2016-02-22 18:56:32.613058614 -0800
+++ b.txt 2016-02-22 18:56:49.219079057 -0800
@@ -3,10 +3,10 @@
wm_linetime = 121
plane_wm level 0 plane 0 = 2147500036
plane_wm level 0 plane 1 = 0
- plane_wm level 0 cursor = 2147500036
+ plane_wm level 0 cursor = 16388
plane_wm level 1 plane 0 = 2147516439
plane_wm level 1 plane 1 = 0
- plane_wm level 1 cursor = 2147516439
+ plane_wm level 1 cursor = 32791
plane_wm level 2 plane 0 = 2147516448
plane_wm level 2 plane 1 = 0
plane_wm level 2 cursor = 0
The code that generated this is attached.
Is the fix from Matt that you mentioned this one:
commit e2e407dc093f530b771ee8bf8fe1be41e3cea8b3
Author: Matt Roper <[email protected]>
Date: Mon Feb 8 11:05:28 2016 -0800
drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
On brief inspection, it doesn't look like that patch will have any
effect on Skylake.
--Andy
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index a234687792f0..cb65f45a75ff 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3318,25 +3318,38 @@ static void skl_write_wm_values(struct drm_i915_private *dev_priv,
struct drm_device *dev = dev_priv->dev;
struct intel_crtc *crtc;
+ pr_info("skl_write_wm_values...\n");
+
for_each_intel_crtc(dev, crtc) {
int i, level, max_level = ilk_wm_max_level(dev);
enum pipe pipe = crtc->pipe;
- if (!new->dirty[pipe])
+ pr_info(" CRTC %s pipe %c\n", crtc->base.name, pipe_name(pipe));
+
+ if (!new->dirty[pipe]) {
+ pr_info(" clean\n");
continue;
+ }
I915_WRITE(PIPE_WM_LINETIME(pipe), new->wm_linetime[pipe]);
+ pr_info(" wm_linetime = %u\n", new->wm_linetime[pipe]);
for (level = 0; level <= max_level; level++) {
- for (i = 0; i < intel_num_planes(crtc); i++)
+ for (i = 0; i < intel_num_planes(crtc); i++) {
+ pr_info(" plane_wm level %d plane %d = %u\n", level, i, new->plane[pipe][i][level]);
I915_WRITE(PLANE_WM(pipe, i, level),
new->plane[pipe][i][level]);
+ }
+ pr_info(" plane_wm level %d cursor = %u\n", level, new->plane[pipe][PLANE_CURSOR][level]);
I915_WRITE(CUR_WM(pipe, level),
new->plane[pipe][PLANE_CURSOR][level]);
}
- for (i = 0; i < intel_num_planes(crtc); i++)
+ for (i = 0; i < intel_num_planes(crtc); i++) {
+ pr_info(" wm_trans plane %d = %u\n", i, new->plane_trans[pipe][i]);
I915_WRITE(PLANE_WM_TRANS(pipe, i),
new->plane_trans[pipe][i]);
+ }
+ pr_info(" wm_trans cursor = %u\n", new->plane_trans[pipe][PLANE_CURSOR]);
I915_WRITE(CUR_WM_TRANS(pipe),
new->plane_trans[pipe][PLANE_CURSOR]);
@@ -3520,8 +3533,10 @@ static void skl_update_other_pipe_wm(struct drm_device *dev,
* enabled crtcs will keep the same allocation and we don't need to
* recompute anything for them.
*/
- if (!skl_ddb_allocation_changed(&r->ddb, this_crtc))
+ if (!skl_ddb_allocation_changed(&r->ddb, this_crtc)) {
+ pr_info("skl_update_other_pipe_wm(%s): no change\n", crtc->name);
return;
+ }
/*
* Otherwise, because of this_crtc being freshly enabled/disabled, the
@@ -3587,12 +3602,16 @@ static void skl_update_wm(struct drm_crtc *crtc)
skl_clear_wm(results, intel_crtc->pipe);
- if (!skl_update_pipe_wm(crtc, &results->ddb, pipe_wm))
+ if (!skl_update_pipe_wm(crtc, &results->ddb, pipe_wm)) {
+ pr_info("skl_update_wm(%s): no update\n", crtc->name);
return;
+ }
skl_compute_wm_results(dev, pipe_wm, results, intel_crtc);
results->dirty[intel_crtc->pipe] = true;
+ pr_info("skl_update_wm(%s): computed update\n", crtc->name);
+
skl_update_other_pipe_wm(dev, crtc, results);
skl_write_wm_values(dev_priv, results);
skl_flush_wm_values(dev_priv, results);
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