Re: [PATCH 11/14] drm/i915/dp: Use int for compressed BPP in dsc_compute_link_config()

[Imre Deak <imre.deak@intel.com>]

On Fri, Jan 31, 2025 at 05:08:33PM +0200, Imre Deak wrote:
> On Fri, Jan 31, 2025 at 02:50:04PM +0200, Jani Nikula wrote:
> > Just use ints unless there are actual reasons to do otherwise. Here,
> > there are not.
> > 
> > Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 7a8a4df1bf1e..7c6d277729d0 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1926,7 +1926,7 @@ static bool intel_dp_dsc_supports_format(const struct intel_connector *connector
> >  	return drm_dp_dsc_sink_supports_format(connector->dp.dsc_dpcd, sink_dsc_format);
> >  }
> >  
> > -static bool is_bw_sufficient_for_dsc_config(u16 compressed_bppx16, u32 link_clock,
> > +static bool is_bw_sufficient_for_dsc_config(int dsc_bpp_x16, u32 link_clock,
> >  					    u32 lane_count, u32 mode_clock,
> >  					    enum intel_output_format output_format,
> >  					    int timeslots)
> > @@ -1934,7 +1934,7 @@ static bool is_bw_sufficient_for_dsc_config(u16 compressed_bppx16, u32 link_cloc
> >  	u32 available_bw, required_bw;
> >  
> >  	available_bw = (link_clock * lane_count * timeslots * 16)  / 8;
> > -	required_bw = compressed_bppx16 * (intel_dp_mode_to_fec_clock(mode_clock));
> > +	required_bw = dsc_bpp_x16 * (intel_dp_mode_to_fec_clock(mode_clock));
> 
> This reduces the range for dsc_bpp_x16 and mode_clock where the above
> multiply won't overflow, but afaics with the current max values of those
> this is still ok:

Actually it doesn't reduce the range, since intel_dp_mode_to_fec_clock()
returns u32, so nvm the above comment.

> Reviewed-by: Imre Deak <imre.deak@intel.com>
> 
> >  
> >  	return available_bw > required_bw;
> >  }
> > @@ -1942,7 +1942,7 @@ static bool is_bw_sufficient_for_dsc_config(u16 compressed_bppx16, u32 link_cloc
> >  static int dsc_compute_link_config(struct intel_dp *intel_dp,
> >  				   struct intel_crtc_state *pipe_config,
> >  				   const struct link_config_limits *limits,
> > -				   u16 compressed_bppx16,
> > +				   int dsc_bpp_x16,
> >  				   int timeslots)
> >  {
> >  	const struct drm_display_mode *adjusted_mode = &pipe_config->hw.adjusted_mode;
> > @@ -1957,7 +1957,7 @@ static int dsc_compute_link_config(struct intel_dp *intel_dp,
> >  		for (lane_count = limits->min_lane_count;
> >  		     lane_count <= limits->max_lane_count;
> >  		     lane_count <<= 1) {
> > -			if (!is_bw_sufficient_for_dsc_config(compressed_bppx16, link_rate,
> > +			if (!is_bw_sufficient_for_dsc_config(dsc_bpp_x16, link_rate,
> >  							     lane_count, adjusted_mode->clock,
> >  							     pipe_config->output_format,
> >  							     timeslots))
> > -- 
> > 2.39.5
> >