[PATCH v3 11/14] drm/msm/dpu: clean up the self-refresh helpers on teardown

[Dmitry Baryshkov]

Unbinding the display driver on MSM8996 with DPU oopses about a second
later:

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000870
  pc : drm_atomic_commit_alloc+0x10/0x9c
  lr : drm_self_refresh_helper_entry_work+0x5c/0x1dc

dpu_crtc_init() sets up the self-refresh helper for each CRTC, but
nothing ever calls drm_self_refresh_helper_cleanup(). Every modeset
commit, including the one which shuts the display down on unbind, queues
the delayed entry work of the helper, which then runs after the CRTC
and the DRM device have been freed, and its data is leaked.

Clean the helpers up when tearing down the DPU hardware, which cancels
the pending work while the KMS is still intact. Doing it from a managed
action instead would not be enough: the DRM device, and its managed
resources with it, outlives the unbind as long as userspace holds it
open.

Fixes: 1122697810e5 ("drm/msm/disp/dpu: add PSR support for eDP interface in dpu driver")
Assisted-by: LLM
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
index 65ba8fa697e9..934ba47b2dae 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
@@ -17,6 +17,7 @@
 #include <drm/drm_crtc.h>
 #include <drm/drm_file.h>
 #include <drm/drm_framebuffer.h>
+#include <drm/drm_self_refresh_helper.h>
 #include <drm/drm_vblank.h>
 #include <drm/drm_writeback.h>
 
@@ -885,8 +886,18 @@ static int _dpu_kms_drm_obj_init(struct dpu_kms *dpu_kms)
 	return 0;
 }
 
+static void dpu_kms_self_refresh_cleanup(struct dpu_kms *dpu_kms)
+{
+	struct drm_crtc *crtc;
+
+	drm_for_each_crtc(crtc, dpu_kms->dev)
+		drm_self_refresh_helper_cleanup(crtc);
+}
+
 static void _dpu_kms_hw_destroy(struct dpu_kms *dpu_kms)
 {
+	dpu_kms_self_refresh_cleanup(dpu_kms);
+
 	dpu_kms->hw_intr = NULL;
 
 	/* safe to call these more than once during shutdown */

-- 
2.47.3