[Intel-gfx] [RFC v4 5/6] drm/i915/dp: Change a link bandwidth computation for DP YCbCr 4:2:0 output
Mun, Gwan-gyeong
gwan-gyeong.mun at intel.com
Thu Mar 7 20:31:42 UTC 2019
On Wed, 2019-03-06 at 23:04 +0200, Ville Syrjälä wrote:
> On Wed, Mar 06, 2019 at 09:31:01PM +0200, Gwan-gyeong Mun wrote:
> > All of the link bandwidth and Data M/N calculations were assumed a
> > bpp as
> > RGB format. But When we are using YCbCr 4:2:0 output format on DP,
> > we should change bpp calculations as YCbCr 4:2:0 format.
> > The pipe_bpp value was assumed RGB format, therefore, it was
> > multiplied
> > with 3. But YCbCr 4:2:0 requires a multiplier value to 1.5.
> > Therefore we need to divide pipe_bpp to 2 while DP output uses
> > YCbCr4:2:0
> > format.
> > - RGB format bpp = bpc x 3
> > - YCbCr 4:2:0 format bpp = bpc x 1.5
> >
> > And it adds missed bpc values for a programming of VSC Header.
> > It only affects dp and edp port which use YCbCr 4:2:0 output
> > format.
> > And for now, it does not consider a use case of DSC + YCbCr 4:2:0.
> >
> > v2:
> > Addressed review comments from Ville.
> > Remove a changing of pipe_bpp on intel_ddi_set_pipe_settings().
> > Because the pipe is running at the full bpp, keep pipe_bpp as RGB
> > even though YCbCr 4:2:0 output format is used.
> > Add a link bandwidth computation for YCbCr4:2:0 output format.
> >
> > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 64
> > +++++++++++++++++++++++++++++----
> > 1 file changed, 57 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > b/drivers/gpu/drm/i915/intel_dp.c
> > index 74f051428fb2..c6826cda8c5f 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1723,7 +1723,8 @@ void intel_dp_compute_rate(struct intel_dp
> > *intel_dp, int port_clock,
> > struct link_config_limits {
> > int min_clock, max_clock;
> > int min_lane_count, max_lane_count;
> > - int min_bpp, max_bpp;
> > + int min_bpp, max_bpp, bpp_step;
> > + bool is_ycbcr420;
> > };
> >
> > static bool intel_dp_source_supports_fec(struct intel_dp
> > *intel_dp,
> > @@ -1833,7 +1834,7 @@ intel_dp_compute_link_config_wide(struct
> > intel_dp *intel_dp,
> > int bpp, clock, lane_count;
> > int mode_rate, link_clock, link_avail;
> >
> > - for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 *
> > 3) {
> > + for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -=
> > limits->bpp_step) {
> > mode_rate = intel_dp_link_required(adjusted_mode-
> > >crtc_clock,
> > bpp);
> >
> > @@ -1847,7 +1848,10 @@ intel_dp_compute_link_config_wide(struct
> > intel_dp *intel_dp,
> >
> > if (mode_rate <= link_avail) {
> > pipe_config->lane_count =
> > lane_count;
> > - pipe_config->pipe_bpp = bpp;
> > + if (limits->is_ycbcr420)
> > + pipe_config->pipe_bpp =
> > bpp * 2;
> > + else
> > + pipe_config->pipe_bpp =
> > bpp;
>
> This approach feels needlessly complicated.
>
> Can't we just do something like this?
>
> static int intel_dp_output_bpp(const struct intel_crtc_state
> *crtc_state, int bpp)
> {
> if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420)
> bpp /= 2;
> return bpp;
> }
>
> intel_dp_compute_link_config_*(struct intel_dp *intel_dp,
> {
> ...
> for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 *
> 3) {
> + int output_bpp = intel_dp_output_bpp(pipe_config, bpp);
> +
> mode_rate = intel_dp_link_required(adjusted_mode-
> >crtc_clock,
> - bpp);
> + output_bpp);
>
I agree. Thank you for guiding me.
In order to make codes simple, I'll add and use intel_dp_output_bpp()
function.
>
> > pipe_config->port_clock =
> > link_clock;
> >
> > return 0;
> > @@ -1869,7 +1873,7 @@ intel_dp_compute_link_config_fast(struct
> > intel_dp *intel_dp,
> > int bpp, clock, lane_count;
> > int mode_rate, link_clock, link_avail;
> >
> > - for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 *
> > 3) {
> > + for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -=
> > limits->bpp_step) {
> > mode_rate = intel_dp_link_required(adjusted_mode-
> > >crtc_clock,
> > bpp);
> >
> > @@ -1883,7 +1887,10 @@ intel_dp_compute_link_config_fast(struct
> > intel_dp *intel_dp,
> >
> > if (mode_rate <= link_avail) {
> > pipe_config->lane_count =
> > lane_count;
> > - pipe_config->pipe_bpp = bpp;
> > + if (limits->is_ycbcr420)
> > + pipe_config->pipe_bpp =
> > bpp * 2;
> > + else
> > + pipe_config->pipe_bpp =
> > bpp;
> > pipe_config->port_clock =
> > link_clock;
> >
> > return 0;
> > @@ -2015,6 +2022,8 @@ intel_dp_compute_link_config(struct
> > intel_encoder *encoder,
> > struct link_config_limits limits;
> > int common_len;
> > int ret;
> > + bool is_ycbcr420 =
> > + pipe_config->output_format ==
> > INTEL_OUTPUT_FORMAT_YCBCR420 ? true : false;
> >
> > common_len = intel_dp_common_len_rate_limit(intel_dp,
> > intel_dp-
> > >max_link_rate);
> > @@ -2030,6 +2039,20 @@ intel_dp_compute_link_config(struct
> > intel_encoder *encoder,
> >
> > limits.min_bpp = 6 * 3;
> > limits.max_bpp = intel_dp_compute_bpp(intel_dp, pipe_config);
> > + limits.bpp_step = 2 * 3;
> > +
> > + limits.is_ycbcr420 = is_ycbcr420;
> > +
> > + if (is_ycbcr420) {
> > + /*
> > + * bpp value was assumed to RGB therefore it was
> > multiplied
> > + * with 3. But YCbCr 4:2:0 requires multiplier value to
> > 1.5
> > + * therefore it divides pipe_bpp to 2.
> > + */
> > + limits.min_bpp /= 2;
> > + limits.max_bpp /= 2;
> > + limits.bpp_step /= 2;
> > + }
> >
> > if (intel_dp_is_edp(intel_dp) && intel_dp->edp_dpcd[0] <
> > DP_EDP_14) {
> > /*
> > @@ -2224,13 +2247,23 @@ intel_dp_compute_config(struct
> > intel_encoder *encoder,
> > intel_conn_state->broadcast_rgb ==
> > INTEL_BROADCAST_RGB_LIMITED;
> > }
> >
> > - if (!pipe_config->dsc_params.compression_enable)
> > - intel_link_compute_m_n(pipe_config->pipe_bpp,
> > + if (!pipe_config->dsc_params.compression_enable) {
> > + /*
> > + * Basically, pipe_bpp value is assumed to RGB.
> > + * And on the calculation of Data M and Data N, YCbCr
> > 4:2:0
> > + * output format of the number of bytes per pixel will
> > be half
> > + * the number of bytes of RGB pixel.
> > + */
> > + int pipe_bpp = pipe_config->output_format ==
> > INTEL_OUTPUT_FORMAT_YCBCR420 ?
> > + pipe_config->pipe_bpp / 2 : pipe_config-
> > >pipe_bpp;
> > +
> > + intel_link_compute_m_n(pipe_bpp,
> > pipe_config->lane_count,
> > adjusted_mode->crtc_clock,
> > pipe_config->port_clock,
> > &pipe_config->dp_m_n,
> > constant_n);
> > + }
> > else
> > intel_link_compute_m_n(pipe_config-
> > >dsc_params.compressed_bpp,
> > pipe_config->lane_count,
> > @@ -4458,6 +4491,23 @@ intel_pixel_encoding_setup_vsc(struct
> > intel_dp *intel_dp,
> > * 100b = 16bpc.
> > */
> > vsc_sdp.DB17 = 0x1;
> > + switch (crtc_state->pipe_bpp / 3) {
> > + case 8: /* 8bpc */
> > + vsc_sdp.DB17 = 0x1;
> > + break;
> > + case 10: /* 10bpc */
> > + vsc_sdp.DB17 = 0x2;
> > + break;
> > + case 12: /* 12bpc */
> > + vsc_sdp.DB17 = 0x3;
> > + break;
> > + case 16: /* 16bpc */
> > + vsc_sdp.DB17 = 0x4;
> > + break;
> > + default:
> > + DRM_DEBUG_KMS("Invalid bpp value '%d'\n", crtc_state-
> > >pipe_bpp);
> > + break;
> > + }
> >
> > /*
> > * Content Type (Bits 2:0)
> > --
> > 2.21.0
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