Re: [Intel-gfx] [PATCH v2] drm/i915/display: Fix the 12 BPC bits for PIPE_MISC reg

["Shankar, Uma" <uma.shankar@intel.com>]

> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal@intel.com>
> Sent: Monday, August 2, 2021 6:27 PM
> To: intel-gfx@lists.freedesktop.org
> Cc: Shankar, Uma <uma.shankar@intel.com>; Zanoni, Paulo R
> <paulo.r.zanoni@intel.com>; ville.syrjala@linux.intel.com; daniel.vetter@ffwll.ch;
> jani.nikula@linux.intel.com; joonas.lahtinen@linux.intel.com; Vivi, Rodrigo
> <rodrigo.vivi@intel.com>; stable@vger.kernel.org
> Subject: [PATCH v2] drm/i915/display: Fix the 12 BPC bits for PIPE_MISC reg
> 
> From: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> 
> Till DISPLAY12 the PIPE_MISC bits 5-7 are used to set the Dithering BPC, with valid
> values of 6, 8, 10 BPC, with Dithering bit enabled.
> Also, these bits are used in case of HW readout for pipe_bpp in case of DSI.
> For ADLP+ these bits are used to set the PORT OUTPUT BPC, with valid values of: 6,
> 8, 10, 12 BPC, and need to be programmed whether dithering is enabled or not.
> 
> This patch:
> -corrects the bits 5-7 for PIPE MISC register for 12 BPC.
> -renames the bits and mask to have generic names for these bits for dithering bpc
> and port output bpc.
> 
> v2: Addressed the comments and suggestions from Uma Shankar:
> -Add 'display' in subject
> -Add Fixes tag in the commit message.
> -Take care of DSI case which uses the bits for getting pipe_bpp.
> 
> Fixes: 756f85cffef2 ("drm/i915/bdw: Broadwell has PIPEMISC")
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com> (v1)
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v3.13+
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 18 +++++++++---------
>  drivers/gpu/drm/i915/i915_reg.h              | 15 ++++++++++-----
>  2 files changed, 19 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> b/drivers/gpu/drm/i915/display/intel_display.c
> index 65ddb6c..9766b36 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -5760,16 +5760,16 @@ static void bdw_set_pipemisc(const struct
> intel_crtc_state *crtc_state)
> 
>  	switch (crtc_state->pipe_bpp) {
>  	case 18:
> -		val |= PIPEMISC_DITHER_6_BPC;
> +		val |= PIPEMISC_6_BPC;
>  		break;
>  	case 24:
> -		val |= PIPEMISC_DITHER_8_BPC;
> +		val |= PIPEMISC_8_BPC;
>  		break;
>  	case 30:
> -		val |= PIPEMISC_DITHER_10_BPC;
> +		val |= PIPEMISC_10_BPC;
>  		break;
>  	case 36:
> -		val |= PIPEMISC_DITHER_12_BPC;
> +		val |= PIPEMISC_12_BPC;

Isn't this bit not supported on prior to Gen13 platforms, so from that perspective it's an
Invalid operation. Can you confirm.

>  		break;
>  	default:
>  		MISSING_CASE(crtc_state->pipe_bpp);
> @@ -5822,14 +5822,14 @@ int bdw_get_pipemisc_bpp(struct intel_crtc *crtc)
> 
>  	tmp = intel_de_read(dev_priv, PIPEMISC(crtc->pipe));
> 
> -	switch (tmp & PIPEMISC_DITHER_BPC_MASK) {
> -	case PIPEMISC_DITHER_6_BPC:
> +	switch (tmp & PIPEMISC_BPC_MASK) {
> +	case PIPEMISC_6_BPC:
>  		return 18;
> -	case PIPEMISC_DITHER_8_BPC:
> +	case PIPEMISC_8_BPC:
>  		return 24;
> -	case PIPEMISC_DITHER_10_BPC:
> +	case PIPEMISC_10_BPC:
>  		return 30;
> -	case PIPEMISC_DITHER_12_BPC:
> +	case PIPEMISC_12_BPC:
>  		return 36;

Same here.

>  	default:
>  		MISSING_CASE(tmp);
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 943fe48..bbfe4f4 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -6166,11 +6166,16 @@ enum {
>  #define   PIPEMISC_HDR_MODE_PRECISION	(1 << 23) /* icl+ */
>  #define   PIPEMISC_OUTPUT_COLORSPACE_YUV  (1 << 11)
>  #define   PIPEMISC_PIXEL_ROUNDING_TRUNC	REG_BIT(8) /* tgl+ */
> -#define   PIPEMISC_DITHER_BPC_MASK	(7 << 5)
> -#define   PIPEMISC_DITHER_8_BPC		(0 << 5)
> -#define   PIPEMISC_DITHER_10_BPC	(1 << 5)
> -#define   PIPEMISC_DITHER_6_BPC		(2 << 5)
> -#define   PIPEMISC_DITHER_12_BPC	(3 << 5)
> +/*
> + * For Display < 13, Bits 5-7 of PIPE MISC represent DITHER BPC.
> + * ADLP+, the bits 5-7 represent PORT OUTPUT BPC with valid values of:
> + * 6, 8, 10, 12 BPC.
> + */
> +#define   PIPEMISC_BPC_MASK		(7 << 5)
> +#define   PIPEMISC_8_BPC		(0 << 5)
> +#define   PIPEMISC_10_BPC		(1 << 5)
> +#define   PIPEMISC_6_BPC		(2 << 5)
> +#define   PIPEMISC_12_BPC		(4 << 5) /* adlp+ */
>  #define   PIPEMISC_DITHER_ENABLE	(1 << 4)
>  #define   PIPEMISC_DITHER_TYPE_MASK	(3 << 2)
>  #define   PIPEMISC_DITHER_TYPE_SP	(0 << 2)
> --
> 2.8.1