| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.4 315/453] drm/amd/display: Prevent bandwidth overflow | Date | Mon, 28 Dec 2020 13:49:11 +0100 |
| |
From: Chris Park <Chris.Park@amd.com>
[ Upstream commit 80089dd8410f356d5104496d5ab71a66a4f4646b ]
[Why] At very high pixel clock, bandwidth calculation exceeds 32 bit size and overflow value. This causes the resulting selection of link rate to be inaccurate.
[How] Change order of operation and use fixed point to deal with integer accuracy. Also address bug found when forcing link rate.
Signed-off-by: Chris Park <Chris.Park@amd.com> Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com> Acked-by: Eryk Brol <eryk.brol@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/core/dc_link.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c index 47cefc05fd3f5..f933791f1fbbb 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c @@ -2906,11 +2906,14 @@ uint32_t dc_bandwidth_in_kbps_from_timing( { uint32_t bits_per_channel = 0; uint32_t kbps; + struct fixed31_32 link_bw_kbps; #ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT if (timing->flags.DSC) { - kbps = (timing->pix_clk_100hz * timing->dsc_cfg.bits_per_pixel); - kbps = kbps / 160 + ((kbps % 160) ? 1 : 0); + link_bw_kbps = dc_fixpt_from_int(timing->pix_clk_100hz); + link_bw_kbps = dc_fixpt_div_int(link_bw_kbps, 160); + link_bw_kbps = dc_fixpt_mul_int(link_bw_kbps, timing->dsc_cfg.bits_per_pixel); + kbps = dc_fixpt_ceil(link_bw_kbps); return kbps; } #endif -- 2.27.0
|