Re: [PATCH v18 18/18] drm/i915: Keep plane size mult of 4 for NV12

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Mar 29, 2018 at 01:36:02PM +0530, Vidya Srinivas wrote:
> As per display WA 1106, to avoid corruption issues
> NV12 plane height needs to be multiplier of 4
> Hence we modify the fb src and destination height
> and width to be multiples of 4. Without this, pipe
> fifo underruns were seen on APL and KBL.
> 
> 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 | 8 ++++++++
>  2 files changed, 10 insertions(+)
> 
> 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 538d938..9f466c6 100644
> --- a/drivers/gpu/drm/i915/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> @@ -261,6 +261,14 @@ skl_update_plane(struct intel_plane *plane,
>  	crtc_w--;
>  	crtc_h--;
>  
> +	if (fb->format->format == DRM_FORMAT_NV12) {
> +		src_w = MULT4(src_w);
> +		src_h = MULT4(src_h);
> +		crtc_w = MULT4(crtc_w);
> +		crtc_h = MULT4(crtc_h);

No macros like this pls. I want to know what it's doing. Also this is
wrong. You can't increase src_w/h without potentially pushing the scale
factor past the hardware limits.

> +		DRM_ERROR("%d %d %d %d\n", src_w, src_h, crtc_w, crtc_h);

No user triggrable errors. Also this doesn't even explain what it's
printing.

> +	}
> +
>  	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
>  
>  	if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
> -- 
> 2.7.4
> 
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-- 
Ville Syrjälä
Intel OTC
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