Re: [PATCH v19 18/18] drm/i915: Set src size restrictions for NV12

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 04-04-18 om 10:29 schreef Srinivas, Vidya:
>
>> -----Original Message-----
>> From: Maarten Lankhorst [mailto:maarten.lankhorst@linux.intel.com]
>> Sent: Wednesday, April 4, 2018 1:40 PM
>> To: Srinivas, Vidya <vidya.srinivas@intel.com>; intel-
>> gfx@lists.freedesktop.org
>> Cc: Lankhorst, Maarten <maarten.lankhorst@intel.com>
>> Subject: Re: [Intel-gfx] [PATCH v19 18/18] drm/i915: Set src size restrictions
>> for NV12
>>
>> Op 04-04-18 om 10:06 schreef Srinivas, Vidya:
>>>> -----Original Message-----
>>>> From: Maarten Lankhorst [mailto:maarten.lankhorst@linux.intel.com]
>>>> Sent: Wednesday, April 4, 2018 1:33 PM
>>>> To: Srinivas, Vidya <vidya.srinivas@intel.com>; intel-
>>>> gfx@lists.freedesktop.org
>>>> Cc: Lankhorst, Maarten <maarten.lankhorst@intel.com>
>>>> Subject: Re: [Intel-gfx] [PATCH v19 18/18] drm/i915: Set src size
>>>> restrictions for NV12
>>>>
>>>> Op 02-04-18 om 11:51 schreef Vidya Srinivas:
>>>>> As per display WA 1106, to avoid corruption issues
>>>>> NV12 plane height needs to be multiplier of 4 We expect the src
>>>>> dimensions to be multiplier of 4 We fail the case where src width or
>>>>> height is not multiple of 4 for NV12.
>>>>> We also set the scaler destination height and width to be multiple
>>>>> of 4. Without this, pipe fifo underruns were seen on APL and KBL. We
>>>>> also skip src trunction/adjustments for NV12 case and handle the
>>>>> sizes directly in skl_update_plane
>>>>>
>>>>> Credits-to: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>>>> Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
>>>>> ---
>>>>>  drivers/gpu/drm/i915/intel_drv.h    |  2 ++
>>>>>  drivers/gpu/drm/i915/intel_sprite.c | 19 ++++++++++++++++---
>>>>>  2 files changed, 18 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/intel_drv.h
>>>>> b/drivers/gpu/drm/i915/intel_drv.h
>>>>> index 9c58da0..a1f718d 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_drv.h
>>>>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>>>>> @@ -159,6 +159,8 @@
>>>>>  #define INTEL_I2C_BUS_DVO 1
>>>>>  #define INTEL_I2C_BUS_SDVO 2
>>>>>
>>>>> +#define MULT4(x) ((x + 3) & ~0x03)
>>>>> +
>>>>>  /* these are outputs from the chip - integrated only
>>>>>     external chips are via DVO or SDVO output */  enum
>>>>> intel_output_type { diff --git a/drivers/gpu/drm/i915/intel_sprite.c
>>>>> b/drivers/gpu/drm/i915/intel_sprite.c
>>>>> index d5dad44..b2292dd 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_sprite.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_sprite.c
>>>>> @@ -255,6 +255,12 @@ skl_update_plane(struct intel_plane *plane,
>>>>>  	uint32_t src_h = drm_rect_height(&plane_state->base.src) >> 16;
>>>>>  	unsigned long irqflags;
>>>>>
>>>>> +	if (fb->format->format == DRM_FORMAT_NV12 &&
>>>>> +		((src_h % 4) != 0 || (src_w % 4) != 0)) {
>>>>> +		DRM_DEBUG_KMS("NV12: src dimensions not valid\n");
>>>>> +		return;
>>>>> +	}
>>>> Also on a side note, don't add DRM_DEBUG_KMS in update_plane or
>>>> disable_plane calls. It can take an arbitrary amount of time,
>>>> resulting in an atomic update failure.
>>> Sure, thank you. These are anyway duplicate checks. I will remove them.
>>> The main one is done in intel_framebuffer_init as suggested by you.
>> They're not duplicate, they're done for related reasons:
>> 1. It doesn't make sense to allow creation of a framebuffer with an invalid
>> width/height if the full width/height cannot be used.
>> 2. The checks in skl_update_scaler are the ones that will reject even showing
>> a subset with invalid width, which can cause the fifo underruns.
> If we don’t keep dest width and height as mult of 4, fifo underruns are seen.
> Shall we reject those also? Then it will be safe. As per my observation,
> We have only two options. Either change it to mult of 4 or reject it :(
> Please suggest.
Reject non multiples of 4. Userspace can adapt. :)

~Maarten
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