[Intel-gfx] [PATCH 04/13] drm/i915/dsb: Fix DSB command buffer size checks

[Manna, Animesh]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Friday, December 16, 2022 6:08 AM
> To: intel-gfx at lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH 04/13] drm/i915/dsb: Fix DSB command buffer
> size checks
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> free_pos is in dwords, DSB_BUF_SIZE in bytes. Directly comparing the two is
> nonsense. Fix it up, and make sure we also account for the 8byte alignment
> requirement for each instruction, and also assume that each instruction
> normally eats two dwords.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

LGTM.
Reviewed-by: Animesh Manna <animesh.manna at intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dsb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c
> b/drivers/gpu/drm/i915/display/intel_dsb.c
> index 6abfd0fc541a..fbcbf9efd039 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -97,7 +97,7 @@ void intel_dsb_indexed_reg_write(struct intel_dsb
> *dsb,
>  	u32 *buf = dsb->cmd_buf;
>  	u32 reg_val;
> 
> -	if (drm_WARN_ON(&dev_priv->drm, dsb->free_pos >=
> DSB_BUF_SIZE)) {
> +	if (drm_WARN_ON(&dev_priv->drm, ALIGN(dsb->free_pos, 2) >
> DSB_BUF_SIZE
> +/ 4 - 2)) {
>  		drm_dbg_kms(&dev_priv->drm, "DSB buffer overflow\n");
>  		return;
>  	}
> @@ -167,7 +167,7 @@ void intel_dsb_reg_write(struct intel_dsb *dsb,
>  	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
>  	u32 *buf = dsb->cmd_buf;
> 
> -	if (drm_WARN_ON(&dev_priv->drm, dsb->free_pos >=
> DSB_BUF_SIZE)) {
> +	if (drm_WARN_ON(&dev_priv->drm, ALIGN(dsb->free_pos, 2) >
> DSB_BUF_SIZE
> +/ 4 - 2)) {
>  		drm_dbg_kms(&dev_priv->drm, "DSB buffer overflow\n");
>  		return;
>  	}
> --
> 2.37.4