Re: 4.9.62: intermittent flicker after upgrade from 4.9.61

[Rainer Fiebig <jrf@mailbox.org>]

Greg KH wrote:
> On Sun, Nov 19, 2017 at 12:56:26PM +0100, Rainer Fiebig wrote:
>> 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
> 
>> 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;
> 
>> 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;
> 
> Ok, so this looks like commit 8777b927b92cf5b6c29f9f9d3c737addea9ac8a7
> upstream which is commit 7de694782cbe7840f2c0de6f1e70f41fc1b8b6e8 in
> 4.9.62.
> 
> I've cc:ed the authors of that patch now.
> 
> Maarten, any hints?  Should I revert this from 4.9-stable, or was there
> a follow-on patch that resolved this issue in mainline?
> 
> thanks,
> 
> greg k-h
> 

OK, after reverting the patches, the flicker *is* gone.

BTW (for the future): Was it the right way to address
stable@vger.kernel.org in this matter or would the bugreport at
freedesktop.org have been enough? I'm a bit unsure about that.

Thanks.
Rainer Fiebig