drm/amd/display: disable SubVP + DRR to prevent underflow

[Why&How]
Temporarily disable SubVP+DRR since Xorg has an architectural limitation
where freesync will not work in a multi monitor configuration. SubVP+DRR
requires that freesync be working.

Whether OS has variable refresh setting enabled or not, the state on
the crtc remains same unless an application requests VRR. Due to this,
there is no way to know whether freesync will actually work or not
while we are on the desktop from the kernel's perspective.

If userspace does not have a limitation with multi-display freesync (for
example wayland), then this feature can be enabled by adding a
dcfeaturemask option to amdgpu on the kernel cmdline like:

amdgpu.dcfeaturemask=0x200

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 5a2e09e97dd5ad101b4c1575917bdde3b18c3d35..c420bce47acb591f859a88cb64f47879c479d280 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1604,6 +1604,11 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
        if (amdgpu_dc_feature_mask & DC_DISABLE_LTTPR_DP2_0)
                init_data.flags.allow_lttpr_non_transparent_mode.bits.DP2_0 = true;
 
+       /* Disable SubVP + DRR config by default */
+       init_data.flags.disable_subvp_drr = true;
+       if (amdgpu_dc_feature_mask & DC_ENABLE_SUBVP_DRR)
+               init_data.flags.disable_subvp_drr = false;
+
        init_data.flags.seamless_boot_edp_requested = false;
 
        if (check_seamless_boot_capability(adev)) {

diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index 2bf0a467d45f8ff9ec7e99cf15bc94d7267e2d56..1fde433786894217e894de1467be1f76868c8ae2 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -409,7 +409,7 @@ struct dc_config {
        bool force_bios_enable_lttpr;
        uint8_t force_bios_fixed_vs;
        int sdpif_request_limit_words_per_umc;
-
+       bool disable_subvp_drr;
 };
 
 enum visual_confirm {

diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c b/drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c
index 3372ede2dc28d867dc2e9f0ab62922781c3753f8..e47828e3b6d5d63c853f617f303303128581b481 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c
@@ -880,6 +880,10 @@ static bool subvp_drr_schedulable(struct dc *dc, struct dc_state *context, struc
        int16_t stretched_drr_us = 0;
        int16_t drr_stretched_vblank_us = 0;
        int16_t max_vblank_mallregion = 0;
+       const struct dc_config *config = &dc->config;
+
+       if (config->disable_subvp_drr)
+               return false;
 
        // Find SubVP pipe
        for (i = 0; i < dc->res_pool->pipe_count; i++) {

diff --git a/drivers/gpu/drm/amd/include/amd_shared.h b/drivers/gpu/drm/amd/include/amd_shared.h
index f175e65b853a001ea1bcc66d8edfd5b726cbc952..e4a22c68517d1dc2be04b452d70ac3b096f5aa86 100644 (file)
--- a/drivers/gpu/drm/amd/include/amd_shared.h
+++ b/drivers/gpu/drm/amd/include/amd_shared.h
@@ -240,6 +240,7 @@ enum DC_FEATURE_MASK {
        DC_DISABLE_LTTPR_DP2_0 = (1 << 6), //0x40, disabled by default
        DC_PSR_ALLOW_SMU_OPT = (1 << 7), //0x80, disabled by default
        DC_PSR_ALLOW_MULTI_DISP_OPT = (1 << 8), //0x100, disabled by default
+       DC_ENABLE_SUBVP_DRR = (1 << 9), // 0x200, disabled by default
 };
 
 enum DC_DEBUG_MASK {