On Thu, Nov 16, 2023 at 03:18:40PM +0200, Imre Deak wrote:
> Simplify intel_dp_max_data_rate() using
> drm_dp_bw_channel_coding_efficiency() to calculate the max data rate for
> both DP1.4 and UHBR link rates. This trades a redundant multiply/divide
> for readability.
>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp.c | 26 ++++++++++++-------------
> 1 file changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 209c27167e057..a93e8f6429d85 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -405,29 +405,27 @@ int intel_dp_effective_data_rate(int pixel_clock, int bpp_x16,
> int
> intel_dp_max_data_rate(int max_link_rate, int max_lanes)
> {
> - if (max_link_rate >= 1000000) {
> - /*
> - * UHBR rates always use 128b/132b channel encoding, and have
> - * 97.71% data bandwidth efficiency. Consider max_link_rate the
> - * link bit rate in units of 10000 bps.
> - */
> - int max_link_rate_kbps = max_link_rate * 10;
> -
> - max_link_rate_kbps = DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate_kbps, 9671), 10000);
> - max_link_rate = max_link_rate_kbps / 8;
> - }
> + int ch_coding_efficiency =
> + drm_dp_bw_channel_coding_efficiency(drm_dp_is_uhbr_rate(max_link_rate));
> + int max_link_rate_kbps = max_link_rate * 10;
>
> + /*
> + * UHBR rates always use 128b/132b channel encoding, and have
> + * 97.71% data bandwidth efficiency. Consider max_link_rate the
> + * link bit rate in units of 10000 bps.
> + */
> /*
> * Lower than UHBR rates always use 8b/10b channel encoding, and have
> * 80% data bandwidth efficiency for SST non-FEC. However, this turns
> - * out to be a nop by coincidence, and can be skipped:
> + * out to be a nop by coincidence:
> *
> * int max_link_rate_kbps = max_link_rate * 10;
> * max_link_rate_kbps = DIV_ROUND_DOWN_ULL(max_link_rate_kbps * 8, 10);
> * max_link_rate = max_link_rate_kbps / 8;
> */
> -
> - return max_link_rate * max_lanes;
> + return DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate_kbps * max_lanes,
> + ch_coding_efficiency),
> + 1000000 * 8);
> }
>
> bool intel_dp_can_bigjoiner(struct intel_dp *intel_dp)
> --
> 2.39.2
--
Ville Syrjälä
Intel
