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| author | Shashank Sharma <shashank.sharma@amd.com> | 2021-08-20 10:20:02 +0530 |
|---|---|---|
| committer | Alex Deucher <alexander.deucher@amd.com> | 2021-08-24 15:35:25 -0400 |
| commit | 7301757ea1fbead24f7c5687f828940a698a95db (patch) | |
| tree | 52f42fe92f6374274343dfc8c25aee3221a0ddd8 /drivers/gpu/drm/amd/amdgpu/atombios_crtc.c | |
| parent | 234b4fd9176c60480190ef4f75cc1b920df58329 (diff) | |
| download | linux-7301757ea1fbead24f7c5687f828940a698a95db.tar.gz linux-7301757ea1fbead24f7c5687f828940a698a95db.tar.bz2 linux-7301757ea1fbead24f7c5687f828940a698a95db.zip | |
drm/amdgpu/OLAND: clip the ref divider max value
This patch limits the ref_div_max value to 100, during the
calculation of PLL feedback reference divider. With current
value (128), the produced fb_ref_div value generates unstable
output at particular frequencies. Radeon driver limits this
value at 100.
On Oland, when we try to setup mode 2048x1280@60 (a bit weird,
I know), it demands a clock of 221270 Khz. It's been observed
that the PLL calculations using values 128 and 100 are vastly
different, and look like this:
+------------------------------------------+
|Parameter |AMDGPU |Radeon |
| | | |
+-------------+----------------------------+
|Clock feedback | |
|divider max | 128 | 100 |
|cap value | | |
| | | |
| | | |
+------------------------------------------+
|ref_div_max | | |
| | 42 | 20 |
| | | |
| | | |
+------------------------------------------+
|ref_div | 42 | 20 |
| | | |
+------------------------------------------+
|fb_div | 10326 | 8195 |
+------------------------------------------+
|fb_div | 1024 | 163 |
+------------------------------------------+
|fb_dev_p | 4 | 9 |
|frac fb_de^_p| | |
+----------------------------+-------------+
With ref_div_max value clipped at 100, AMDGPU driver can also
drive videmode 2048x1280@60 (221Mhz) and produce proper output
without any blanking and distortion on the screen.
PS: This value was changed from 128 to 100 in Radeon driver also, here:
https://github.com/freedesktop/drm-tip/commit/4b21ce1b4b5d262e7d4656b8ececc891fc3cb806
V1:
Got acks from:
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
V2:
- Restricting the changes only for OLAND, just to avoid any regression
for other cards.
- Changed unsigned -> unsigned int to make checkpatch quiet.
V3: Apply the change on SI family (not only oland) (Christian)
Cc: Alex Deucher <Alexander.Deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Eddy Qin <Eddy.Qin@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Diffstat (limited to 'drivers/gpu/drm/amd/amdgpu/atombios_crtc.c')
| -rw-r--r-- | drivers/gpu/drm/amd/amdgpu/atombios_crtc.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_crtc.c b/drivers/gpu/drm/amd/amdgpu/atombios_crtc.c index 159a2a4385a1..afad094f84c2 100644 --- a/drivers/gpu/drm/amd/amdgpu/atombios_crtc.c +++ b/drivers/gpu/drm/amd/amdgpu/atombios_crtc.c @@ -851,7 +851,7 @@ void amdgpu_atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode pll->reference_div = amdgpu_crtc->pll_reference_div; pll->post_div = amdgpu_crtc->pll_post_div; - amdgpu_pll_compute(pll, amdgpu_crtc->adjusted_clock, &pll_clock, + amdgpu_pll_compute(adev, pll, amdgpu_crtc->adjusted_clock, &pll_clock, &fb_div, &frac_fb_div, &ref_div, &post_div); amdgpu_atombios_crtc_program_ss(adev, ATOM_DISABLE, amdgpu_crtc->pll_id, |