On Tue, Jul 13, 2021 at 7:14 PM Grace An gracan@codeaurora.org wrote:

When CONFIG_PROVE_LOCKING is defined, the kernel randomly injects -EDEADLK errors for all the ww_mutex. This results in drm_atomic_get_private_obj_state randomly returning -EDEADLK. However, the mode_fixup functions do not propagate these error codes and return false, causing the atomic commit to fail with -EINVAL instead of retrying.

Change encoder, crtc, and bridge mode_fixup functions to return an int instead of a boolean to indicate success or failure. If any of these functions fail, the mode_fixup function now returns the provided integer error code instead of -EINVAL.

This change needs modifications across drivers, but before submitting the entire change, we want to get feedback on this RFC.

Signed-off-by: Grace An gracan@codeaurora.org

Why don't you just use the various atomic_check hooks we have for this? There you get passed the state and everything, have a full int return value, and things actually work.

->mode_fixup is for compatibility with legacy crtc modeset helpers from the pre-atomic times. If the kerneldoc isn't clear yet, please do a patch to fix that up so that @mode_fixup points at the relevant @atomic_check as the recommended function. -Daniel

---

drivers/gpu/drm/drm_atomic_helper.c | 8 ++++---- drivers/gpu/drm/drm_bridge.c | 4 ++-- include/drm/drm_bridge.h | 2 +- include/drm/drm_modeset_helper_vtables.h | 4 ++-- 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index f2b3e28..d75f09a 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -457,10 +457,10 @@ mode_fixup(struct drm_atomic_state *state) } else if (funcs && funcs->mode_fixup) { ret = funcs->mode_fixup(encoder, &new_crtc_state->mode, &new_crtc_state->adjusted_mode);

•                   if (!ret) {
  

•                   if (ret) {
                            DRM_DEBUG_ATOMIC("[ENCODER:%d:%s] fixup failed\n",
                                             encoder->base.id, encoder->name);
  

•                           return -EINVAL;
  

•                           return ret;
                    }
            }
    }
  

@@ -481,10 +481,10 @@ mode_fixup(struct drm_atomic_state *state)

            ret = funcs->mode_fixup(crtc, &new_crtc_state->mode,
                                    &new_crtc_state->adjusted_mode);

•           if (!ret) {
  

•           if (ret) {
                    DRM_DEBUG_ATOMIC("[CRTC:%d:%s] fixup failed\n",
                                     crtc->base.id, crtc->name);
  

•                   return -EINVAL;
  

•                   return ret;
            }
    }
  
  

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 64f0eff..3ad16b5 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -736,9 +736,9 @@ static int drm_atomic_bridge_check(struct drm_bridge *bridge, if (ret) return ret; } else if (bridge->funcs->mode_fixup) {

•           if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
  

•           if (bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
                                           &crtc_state->adjusted_mode))
  

•                   return -EINVAL;
  

•                   return ret;
    }
  
    return 0;
  

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index 2195daa..5d02dfc 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -153,7 +153,7 @@ struct drm_bridge_funcs { * True if an acceptable configuration is possible, false if the modeset * operation should be rejected. */

•   bool (*mode_fixup)(struct drm_bridge *bridge,
  

•   int (*mode_fixup)(struct drm_bridge *bridge,
                       const struct drm_display_mode *mode,
                       struct drm_display_mode *adjusted_mode);
    /**
  

diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h index f3a4b47..e305c97 100644 --- a/include/drm/drm_modeset_helper_vtables.h +++ b/include/drm/drm_modeset_helper_vtables.h @@ -184,7 +184,7 @@ struct drm_crtc_helper_funcs { * True if an acceptable configuration is possible, false if the modeset * operation should be rejected. */

•   bool (*mode_fixup)(struct drm_crtc *crtc,
  

•   int (*mode_fixup)(struct drm_crtc *crtc,
                       const struct drm_display_mode *mode,
                       struct drm_display_mode *adjusted_mode);
  
  

@@ -599,7 +599,7 @@ struct drm_encoder_helper_funcs { * True if an acceptable configuration is possible, false if the modeset * operation should be rejected. */

•   bool (*mode_fixup)(struct drm_encoder *encoder,
  

•   int (*mode_fixup)(struct drm_encoder *encoder,
                       const struct drm_display_mode *mode,
                       struct drm_display_mode *adjusted_mode);
  
  

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