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| author |   Timur Kristóf <timur.kristof@gmail.com> | 2025-07-31 11:43:52 +0200 |
|---|---|---|
| committer |   Alex Deucher <alexander.deucher@amd.com> | 2025-08-18 18:00:34 -0400 |
| commit | 10507478468f165ea681605d133991ed05cdff62 (patch) | |
| tree | aa2e491446eeb28873b944f4239304d0b631a741 | |
| parent | drm/amd/display: Don't print errors for nonexistent connectors (diff) | |
| download | wireguard-linux-10507478468f165ea681605d133991ed05cdff62.tar.xz wireguard-linux-10507478468f165ea681605d133991ed05cdff62.zip | |
drm/amd/display: Fix fractional fb divider in set_pixel_clock_v3
For later VBIOS versions, the fractional feedback divider is
calculated as the remainder of dividing the feedback divider by
a factor, which is set to 1000000. For reference, see:
- calculate_fb_and_fractional_fb_divider
- calc_pll_max_vco_construct
However, in case of old VBIOS versions that have
set_pixel_clock_v3, they only have 1 byte available for the
fractional feedback divider, and it's expected to be set to the
remainder from dividing the feedback divider by 10.
For reference see the legacy display code:
- amdgpu_pll_compute
- amdgpu_atombios_crtc_program_pll
This commit fixes set_pixel_clock_v3 by dividing the fractional
feedback divider passed to the function by 100000.
Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 027e7acc7e17802ebf28e1edb88a404836ad50d6)
Cc: stable@vger.kernel.org
| -rw-r--r-- | drivers/gpu/drm/amd/display/dc/bios/command_table.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/bios/command_table.c b/drivers/gpu/drm/amd/display/dc/bios/command_table.c index 2bcae0643e61..58e88778da7f 100644 --- a/drivers/gpu/drm/amd/display/dc/bios/command_table.c +++ b/drivers/gpu/drm/amd/display/dc/bios/command_table.c @@ -993,7 +993,7 @@ static enum bp_result set_pixel_clock_v3( allocation.sPCLKInput.usFbDiv = cpu_to_le16((uint16_t)bp_params->feedback_divider); allocation.sPCLKInput.ucFracFbDiv = - (uint8_t)bp_params->fractional_feedback_divider; + (uint8_t)(bp_params->fractional_feedback_divider / 100000); allocation.sPCLKInput.ucPostDiv = (uint8_t)bp_params->pixel_clock_post_divider; |