From: Vitaly Prosyak <[email protected]> The vblank counter callback reads display registers and scanout position without holding reset_domain->sem. During GPU recovery, display commit work can call the callback while reset owns the semaphore for writing. The hardware access then triggers the lockdep_assert_held() in amdgpu_device_skip_hw_access() and sets TAINT_WARN when lockdep is enabled.
Try to acquire the reset semaphore for reading before accessing the hardware, and hold it across the counter and scanout-position reads. If reset is already in progress, return DRM's cached software vblank count instead. This avoids blocking behind reset and avoids accessing display hardware while it is being reset. The cached count is less accurate than the hardware count, but is used only when reset prevents a safe hardware read. This addresses the reset-time warning from this vblank path; it does not suppress or fix unrelated lockdep warnings. Cc: Christian König <[email protected]> Cc: Alex Deucher <[email protected]> Cc: Harry Wentland <[email protected]> Cc: Sunpeng Li <[email protected]> Signed-off-by: Vitaly Prosyak <[email protected]> --- drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c index bac072d73e16..f34150d20a2f 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c @@ -30,6 +30,7 @@ #include <drm/amdgpu_drm.h> #include <drm/drm_drv.h> #include <drm/drm_fb_helper.h> +#include <drm/drm_vblank.h> #include "amdgpu_uvd.h" #include "amdgpu_vce.h" #include "atom.h" @@ -1669,6 +1670,9 @@ u32 amdgpu_get_vblank_counter_kms(struct drm_crtc *crtc) DRM_ERROR("Invalid crtc %u\n", pipe); return -EINVAL; } + if (!down_read_trylock(&adev->reset_domain->sem)) + return drm_crtc_vblank_count(crtc); + /* The hw increments its frame counter at start of vsync, not at start * of vblank, as is required by DRM core vblank counter handling. @@ -1714,6 +1718,7 @@ u32 amdgpu_get_vblank_counter_kms(struct drm_crtc *crtc) DRM_DEBUG_VBL("NULL mode info! Returned count may be wrong.\n"); } + up_read(&adev->reset_domain->sem); return count; } -- 2.43.0
