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/linux/drivers/gpu/drm/amd/amdgpu/ |
H A D | amdgpu_pll.h | diff 7301757ea1fbead24f7c5687f828940a698a95db Fri Aug 20 06:50:02 CEST 2021 Shashank Sharma <shashank.sharma@amd.com> 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>
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H A D | amdgpu_pll.c | diff 7301757ea1fbead24f7c5687f828940a698a95db Fri Aug 20 06:50:02 CEST 2021 Shashank Sharma <shashank.sharma@amd.com> 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>
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H A D | atombios_crtc.c | diff 7301757ea1fbead24f7c5687f828940a698a95db Fri Aug 20 06:50:02 CEST 2021 Shashank Sharma <shashank.sharma@amd.com> 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>
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