drm/amd/display: Prevent VStartup Overflow

[ Upstream commit 29c1c20496a7a9bafe2bc2f833d69aa52e0f2c2d ]

[Why]
For some VR headsets with large blanks, it's possible
to overflow the OTG_VSTARTUP_PARAM:VSTARTUP_START
register. This can lead to incorrect DML calculations
and underflow downstream.

[How]
Min the calcualted max_vstartup_lines with the max
value of the register.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Ryan Seto <ryanseto@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c b/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
index ecfa3c898e09dd837a1c590283a06aeea81bcc04..4285cb7fcbe71929e07313c9de9447557b584e77 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
+++ b/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
@@ -12,6 +12,7 @@
 #define DML2_MAX_FMT_420_BUFFER_WIDTH 4096
 #define DML_MAX_NUM_OF_SLICES_PER_DSC 4
 #define ALLOW_SDPIF_RATE_LIMIT_PRE_CSTATE
+#define DML_MAX_VSTARTUP_START 1023
 
 const char *dml2_core_internal_bw_type_str(enum dml2_core_internal_bw_type bw_type)
 {
@@ -3648,6 +3649,7 @@ static unsigned int CalculateMaxVStartup(
        dml2_printf("DML::%s: vblank_avail = %u\n", __func__, vblank_avail);
        dml2_printf("DML::%s: max_vstartup_lines = %u\n", __func__, max_vstartup_lines);
 #endif
+       max_vstartup_lines = (unsigned int)math_min2(max_vstartup_lines, DML_MAX_VSTARTUP_START);
        return max_vstartup_lines;
 }