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 10:51 schreef Srinivas, Vidya:
>
>> -----Original Message-----
>> From: Maarten Lankhorst [mailto:maarten.lankhorst@linux.intel.com]
>> Sent: Wednesday, April 4, 2018 2:18 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 10:04 schreef Srinivas, Vidya:
>>>> -----Original Message-----
>>>> From: Maarten Lankhorst [mailto:maarten.lankhorst@linux.intel.com]
>>>> Sent: Wednesday, April 4, 2018 1:28 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;
>>>>> +	}
>>>>> +
>>>> You can't do this check in skl_update_plane, it's way too late. It
>>>> should be rejected in the plane check with -EINVAL, or perhaps in
>> skl_update_scaler.
>>> Have done it right from intel_framebuffer_init onwards, have done it
>>> in skl_update_scaler also In fact it will get rejected in framebuffer init and
>> all these are duplicate checks, can remove them.
>>>>>  	/* Sizes are 0 based */
>>>>>  	src_w--;
>>>>>  	src_h--;
>>>>> @@ -292,9 +298,12 @@ skl_update_plane(struct intel_plane *plane,
>>>>>  			      PS_SCALER_EN | PS_PLANE_SEL(plane_id) |
>>>> scaler->mode);
>>>>>  		I915_WRITE_FW(SKL_PS_PWR_GATE(pipe, scaler_id), 0);
>>>>>  		I915_WRITE_FW(SKL_PS_WIN_POS(pipe, scaler_id), (crtc_x
>>>> << 16) | crtc_y);
>>>>> -		I915_WRITE_FW(SKL_PS_WIN_SZ(pipe, scaler_id),
>>>>> -			      ((crtc_w + 1) << 16)|(crtc_h + 1));
>>>>> -
>>>>> +		if (fb->format->format == DRM_FORMAT_NV12)
>>>>> +			I915_WRITE_FW(SKL_PS_WIN_SZ(pipe, scaler_id),
>>>>> +				      (MULT4(crtc_w) << 16) |
>>>> MULT4(crtc_h));
>>>> See the comment above, sizes are 0 based. This will add 1 to the
>>>> size, so the size is always 1 more than requested.
>>>> I don't think it would pass plane CRC tests..
>>> When I align it to mult of 4, 1919 (which was 1920-1) becomes 1920 back.
>>> If we don’t do this, I see fifo underruns. The destination width and
>>> height If not mult of 4, I am seeing underruns.
>> What you see as 1920 is 1921, which should be underrunning even more and
>> is out of FB bounds.
> Sorry, I gave a wrong example here. It doesn’t happen when we scale it to full resolution.
> It happened during other testing when the scaled dest width or height was not
> multiple of 4.
>  

We could reject it, but odd that crtc w/h matters. I didn't expect that. :)

Rejecting with -EINVAL is the best way to go, along with documentation in the form of tests that we handle this case correctly.

~Maarten

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