Re: 4.9.62: intermittent flicker after upgrade from 4.9.61

[Rainer Fiebig <jrf@mailbox.org>]

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Greg KH wrote:
> On Sat, Nov 18, 2017 at 05:08:20PM +0100, Rainer Fiebig wrote:
>> Greg KH wrote:
>>> On Sat, Nov 18, 2017 at 01:47:32PM +0100, Rainer Fiebig wrote:
>>>> Hi!
>>>>
>>>> Hopefully the right addressee.
>>>>
>>>> Encountered two bad backports which cause screen-flicker.
>>>> dmesg shows:
>>>>
>>>> ...
>>>> [drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
>>>> [drm:ironlake_irq_handler [i915]] *ERROR* PCH transcoder A FIFO underrun
>>>> [drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun
>>>> [drm:ironlake_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun
>>>> ...
>>>>
>>>> CPU: Intel Core i3 (Clarkdale/Ironlake)
>>>>
>>>> The backports are:
>>>>
>>>> - diff --git a/drivers/gpu/drm/i915/intel_pm.c
>>>> b/drivers/gpu/drm/i915/intel_pm.c
>>>>     index 49de476..277a802 100644
>>>> - diff --git a/drivers/gpu/drm/i915/intel_drv.h
>>>> b/drivers/gpu/drm/i915/intel_drv.h
>>>>     index a19ec06..3ce9ba3 100644
>>>>
>>>> After reversing them the flicker is gone, no more messages in dmesg. All
>>>> else OK so far.
>>>
>>> So which commit was the one that caused the problem?  I will be glad to
>>> revert it.
>>>
>>> thanks,
>>>
>>> greg k-h
>>>
>>>
>>
>> I started by reverting the more complex one first ("index
>> 49de476..277a802100644"). But the kernel wouldn't compile then.
> 
> What git commit id is that?  I don't see those ids in the 4.9-stable
> tree.
> 
>> So I also reverted "index a19ec06..3ce9ba3 100644". After that the
>> kernel compiled just fine and the problems were gone (still are).
> 
> Same here, what git commit id was this?
> 
> thanks,
> 
> greg k-h
> 

OK, no mistake. IIRC, I took the patches (and the IDs) from the
changelog for patch-4.9.62. I've attached both, so you can check yourself.

I've also applied a freshly downloaded patch-4.9.62 to a freshly
expanded 4.9 and re-compiled. The flicker is there. I haven't yet
reverted the two patches but I'm confident that after having done so the
flicker will be gone. If not I'll let you know.

As a good news: 4.14 is *not* affected. So to me it seems those two
patches are part of sort of a package and can not be backported alone.

So long!
Rainer Fiebig

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diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 49de476..277a802 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -27,6 +27,7 @@
 
 #include <linux/cpufreq.h>
 #include <drm/drm_plane_helper.h>
+#include <drm/drm_atomic_helper.h>
 #include "i915_drv.h"
 #include "intel_drv.h"
 #include "../../../platform/x86/intel_ips.h"
@@ -2017,9 +2018,9 @@ static void ilk_compute_wm_level(const struct drm_i915_private *dev_priv,
 				 const struct intel_crtc *intel_crtc,
 				 int level,
 				 struct intel_crtc_state *cstate,
-				 struct intel_plane_state *pristate,
-				 struct intel_plane_state *sprstate,
-				 struct intel_plane_state *curstate,
+				 const struct intel_plane_state *pristate,
+				 const struct intel_plane_state *sprstate,
+				 const struct intel_plane_state *curstate,
 				 struct intel_wm_level *result)
 {
 	uint16_t pri_latency = dev_priv->wm.pri_latency[level];
@@ -2341,28 +2342,24 @@ static int ilk_compute_pipe_wm(struct intel_crtc_state *cstate)
 	struct intel_pipe_wm *pipe_wm;
 	struct drm_device *dev = state->dev;
 	const struct drm_i915_private *dev_priv = to_i915(dev);
-	struct intel_plane *intel_plane;
-	struct intel_plane_state *pristate = NULL;
-	struct intel_plane_state *sprstate = NULL;
-	struct intel_plane_state *curstate = NULL;
+	struct drm_plane *plane;
+	const struct drm_plane_state *plane_state;
+	const struct intel_plane_state *pristate = NULL;
+	const struct intel_plane_state *sprstate = NULL;
+	const struct intel_plane_state *curstate = NULL;
 	int level, max_level = ilk_wm_max_level(dev), usable_level;
 	struct ilk_wm_maximums max;
 
 	pipe_wm = &cstate->wm.ilk.optimal;
 
-	for_each_intel_plane_on_crtc(dev, intel_crtc, intel_plane) {
-		struct intel_plane_state *ps;
+	drm_atomic_crtc_state_for_each_plane_state(plane, plane_state, &cstate->base) {
+		const struct intel_plane_state *ps = to_intel_plane_state(plane_state);
 
-		ps = intel_atomic_get_existing_plane_state(state,
-							   intel_plane);
-		if (!ps)
-			continue;
-
-		if (intel_plane->base.type == DRM_PLANE_TYPE_PRIMARY)
+		if (plane->type == DRM_PLANE_TYPE_PRIMARY)
 			pristate = ps;
-		else if (intel_plane->base.type == DRM_PLANE_TYPE_OVERLAY)
+		else if (plane->type == DRM_PLANE_TYPE_OVERLAY)
 			sprstate = ps;
-		else if (intel_plane->base.type == DRM_PLANE_TYPE_CURSOR)
+		else if (plane->type == DRM_PLANE_TYPE_CURSOR)
 			curstate = ps;
 	}
 
@@ -2384,11 +2381,9 @@ static int ilk_compute_pipe_wm(struct intel_crtc_state *cstate)
 	if (pipe_wm->sprites_scaled)
 		usable_level = 0;
 
-	ilk_compute_wm_level(dev_priv, intel_crtc, 0, cstate,
-			     pristate, sprstate, curstate, &pipe_wm->raw_wm[0]);
-
 	memset(&pipe_wm->wm, 0, sizeof(pipe_wm->wm));
-	pipe_wm->wm[0] = pipe_wm->raw_wm[0];
+	ilk_compute_wm_level(dev_priv, intel_crtc, 0, cstate,
+			     pristate, sprstate, curstate, &pipe_wm->wm[0]);
 
 	if (IS_HASWELL(dev) || IS_BROADWELL(dev))
 		pipe_wm->linetime = hsw_compute_linetime_wm(cstate);
@@ -2398,8 +2393,8 @@ static int ilk_compute_pipe_wm(struct intel_crtc_state *cstate)
 
 	ilk_compute_wm_reg_maximums(dev, 1, &max);
 
-	for (level = 1; level <= max_level; level++) {
-		struct intel_wm_level *wm = &pipe_wm->raw_wm[level];
+	for (level = 1; level <= usable_level; level++) {
+		struct intel_wm_level *wm = &pipe_wm->wm[level];
 
 		ilk_compute_wm_level(dev_priv, intel_crtc, level, cstate,
 				     pristate, sprstate, curstate, wm);
@@ -2409,13 +2404,10 @@ static int ilk_compute_pipe_wm(struct intel_crtc_state *cstate)
 		 * register maximums since such watermarks are
 		 * always invalid.
 		 */
-		if (level > usable_level)
-			continue;
-
-		if (ilk_validate_wm_level(level, &max, wm))
-			pipe_wm->wm[level] = *wm;
-		else
-			usable_level = level;
+		if (!ilk_validate_wm_level(level, &max, wm)) {
+			memset(wm, 0, sizeof(*wm));
+			break;
+		}
 	}
 
 	return 0;

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diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index a19ec06..3ce9ba3 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -457,7 +457,6 @@ struct intel_crtc_scaler_state {
 
 struct intel_pipe_wm {
 	struct intel_wm_level wm[5];
-	struct intel_wm_level raw_wm[5];
 	uint32_t linetime;
 	bool fbc_wm_enabled;
 	bool pipe_enabled;