From: Ilya Bakoulin ilya.bakoulin@amd.com
[ Upstream commit 94bbf802efd0a8f13147d6664af6e653637340a8 ]
Changing PBN calculation to be more in line with spec. We don't need to inflate PBN_NATIVE value by the 1.006 margin, since that is already taken care of in the get_pbn_per_slot function.
Tested-by: Daniel Wheeler daniel.wheeler@amd.com Reviewed-by: Wenjing Liu wenjing.liu@amd.com Acked-by: Rodrigo Siqueira rodrigo.siqueira@amd.com Signed-off-by: Ilya Bakoulin ilya.bakoulin@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/amd/display/dc/link/link_dpms.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c index f8e01ca09d96..a3b3aec05d6b 100644 --- a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c +++ b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c @@ -1057,18 +1057,21 @@ static struct fixed31_32 get_pbn_from_bw_in_kbps(uint64_t kbps) uint32_t denominator = 1;
/* - * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006 + * The 1.006 factor (margin 5300ppm + 300ppm ~ 0.6% as per spec) is not + * required when determining PBN/time slot utilization on the link between + * us and the branch, since that overhead is already accounted for in + * the get_pbn_per_slot function. + * * 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 *= (1006/1000) * peak_kbps *= (64/54) - * peak_kbps *= 8 convert to bytes + * peak_kbps /= (8 * 1000) convert to bytes */
- numerator = 64 * PEAK_FACTOR_X1000; - denominator = 54 * 8 * 1000 * 1000; + numerator = 64; + denominator = 54 * 8 * 1000; kbps *= numerator; peak_kbps = dc_fixpt_from_fraction(kbps, denominator);