With DSC, bpp can be a multiple of 1/16, so drm_dp_calc_pbn_mode is insufficient. Add drm_dp_calc_pbn_mode_dsc, a function which is the same as drm_dp_calc_pbn_mode, but the bpp is in units of 1/16. Cc: Lyude Paul <lyude@xxxxxxxxxx> Cc: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx> Signed-off-by: David Francis <David.Francis@xxxxxxx> --- drivers/gpu/drm/drm_dp_mst_topology.c | 43 +++++++++++++++++++++++++++ include/drm/drm_dp_mst_helper.h | 2 +- 2 files changed, 44 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 398e7314ea8b..34a5bdfc598b 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3588,6 +3588,49 @@ static int test_calc_pbn_mode(void) return 0; } +/** + * drm_dp_calc_pbn_mode_dsc() - Calculate the PBN for a mode with DSC enabled. + * @clock: dot clock for the mode + * @dsc_bpp: dsc bits per pixel x16 (e.g. dsc_bpp = 136 is 8.5 bpp) + * + * This uses the formula in the spec to calculate the PBN value for a mode, + * given that the mode is using DSC + * Returns: + * PBN required for this mode + */ +int drm_dp_calc_pbn_mode_dsc(int clock, int dsc_bpp) +{ + u64 kbps; + s64 peak_kbps; + u32 numerator; + u32 denominator; + + kbps = clock * dsc_bpp; + + /* + * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006 + * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on + * common multiplier to render an integer PBN for all link rate/lane + * counts combinations + * calculate + * peak_kbps *= (1/16) bppx16 to bpp + * peak_kbps *= (1006/1000) + * peak_kbps *= (64/54) + * peak_kbps *= 8 convert to bytes + * + * Divide numerator and denominator by 16 to avoid overflow + */ + + numerator = 64 * 1006 / 16; + denominator = 54 * 8 * 1000 * 1000; + + kbps *= numerator; + peak_kbps = drm_fixp_from_fraction(kbps, denominator); + + return drm_fixp2int_ceil(peak_kbps); +} +EXPORT_SYMBOL(drm_dp_calc_pbn_mode_dsc); + /* we want to kick the TX after we've ack the up/down IRQs. */ static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr) { diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 2ba6253ea6d3..ddb518f2157a 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -611,7 +611,7 @@ struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_ int drm_dp_calc_pbn_mode(int clock, int bpp); - +int drm_dp_calc_pbn_mode_dsc(int clock, int dsc_bpp); bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, int pbn, int slots); -- 2.17.1 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel