Re: [PATCH v9 01/24] drm/dsc: Modify DRM helper to return complete DSC color depth capabilities

[Manasi Navare <manasi.d.navare@intel.com>]

On Mon, Nov 19, 2018 at 09:43:38PM +0200, Ville Syrjälä wrote:
> On Tue, Nov 13, 2018 at 05:52:09PM -0800, Manasi Navare wrote:
> > DSC DPCD color depth register advertises its color depth capabilities
> > by setting each of the bits that corresponding to a specific color
> > depth. This patch defines those specific color depths and adds
> > a helper to return an array of color depth capabilities.
> > 
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_dp_helper.c | 29 +++++++++++++++++++----------
> >  include/drm/drm_dp_helper.h     |  9 +++++----
> >  2 files changed, 24 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> > index 6d483487f2b4..286567063960 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -1428,17 +1428,26 @@ u8 drm_dp_dsc_sink_line_buf_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
> >  }
> >  EXPORT_SYMBOL(drm_dp_dsc_sink_line_buf_depth);
> >  
> > -u8 drm_dp_dsc_sink_max_color_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
> > +void drm_dp_dsc_sink_color_depth_cap(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE],
> > +				     u8 *dsc_sink_color_depth_cap)
> >  {
> > +	int i, cnt = 0;
> >  	u8 color_depth = dsc_dpcd[DP_DSC_DEC_COLOR_DEPTH_CAP - DP_DSC_SUPPORT];
> >  
> > -	if (color_depth & DP_DSC_12_BPC)
> > -		return 12;
> > -	if (color_depth & DP_DSC_10_BPC)
> > -		return 10;
> > -	if (color_depth & DP_DSC_8_BPC)
> > -		return 8;
> > -
> > -	return 0;
> > +	for (i = 1; i <= 3; i++) {
> > +		if (!(color_depth & BIT(i)))
> > +			continue;
> > +		switch (i) {
> > +		case 1:
> > +			dsc_sink_color_depth_cap[cnt++] = DP_DSC_8_BPC;
> > +			break;
> > +		case 2:
> > +			dsc_sink_color_depth_cap[cnt++] = DP_DSC_10_BPC;
> > +			break;
> > +		case 3:
> > +			dsc_sink_color_depth_cap[cnt++] = DP_DSC_12_BPC;
> > +			break;
> > +		}
> > +	}
> >  }
> > -EXPORT_SYMBOL(drm_dp_dsc_sink_max_color_depth);
> > +EXPORT_SYMBOL(drm_dp_dsc_sink_color_depth_cap);
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index 3314e91f6eb3..ea3233b0a790 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -242,9 +242,9 @@
> >  # define DP_DSC_YCbCr420_Native             (1 << 4)
> >  
> >  #define DP_DSC_DEC_COLOR_DEPTH_CAP          0x06A
> > -# define DP_DSC_8_BPC                       (1 << 1)
> > -# define DP_DSC_10_BPC                      (1 << 2)
> > -# define DP_DSC_12_BPC                      (1 << 3)
> > +# define DP_DSC_8_BPC                       8
> > +# define DP_DSC_10_BPC                      10
> > +# define DP_DSC_12_BPC                      12
> 
> 
> I'd suggest something simpler like:
> 
> int foo(u8 bpc[3])

Is passing a full array recommended method vs passing the pointer to the array?

> {
> 	int num_bpc = 0;
> 
> 	if (color_depth & DP_DSC_12_BPC)
> 		bpc[num_bpc++] = 12;
> 	if (color_depth & DP_DSC_10_BPC)
> 		bpc[num_bpc++] = 10;
> 	if (color_depth & DP_DSC_8_BPC)
> 		bpc[num_bpc++] = 8;
> 
> 	return num_bpc;
> }

Yes I could modify like above except start from lowest bpc in bpc[0] going all the way to highest.
Also as of now its only 3 bpcs so its safe to just have an array for 3 bpcs for now right?

Manasi

> 
> >  
> >  #define DP_DSC_PEAK_THROUGHPUT              0x06B
> >  # define DP_DSC_THROUGHPUT_MODE_0_MASK      (0xf << 0)
> > @@ -1123,7 +1123,8 @@ drm_dp_is_branch(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
> >  u8 drm_dp_dsc_sink_max_slice_count(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE],
> >  				   bool is_edp);
> >  u8 drm_dp_dsc_sink_line_buf_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]);
> > -u8 drm_dp_dsc_sink_max_color_depth(const u8 dsc_dpc[DP_DSC_RECEIVER_CAP_SIZE]);
> > +void drm_dp_dsc_sink_color_depth_cap(const u8 dsc_dpc[DP_DSC_RECEIVER_CAP_SIZE],
> > +				     u8 *dsc_sink_color_depth_cap);
> >  
> >  static inline bool
> >  drm_dp_sink_supports_dsc(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
> > -- 
> > 2.19.1
> 
> -- 
> Ville Syrjälä
> Intel
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