[PATCH v5 1/2] drm/bridge: ti-sn65dsi83: Fix error handling in sn65dsi83_reset_work()

[Esben Haabendal]

The error handling of sn65dsi83_reset_pipe() in sn65dsi83_reset_work() has
seen a couple of changes that seems to cause a bit of confusion.

While sn65dsi83_reset_work() has implemented an early exit if
sn65dsi83_reset_pipe() fails since it was added, when a commit from Maxime
Ripard switched to use drm_bridge_helper_reset_crtc() [1] the
sn65dsi83_reset_pipe() function would no longer return an error code, so
the early exit was then a no-op, and even on sn65dsi83_reset_pipe()
failure, enable_irq() has been called.

When drm_bridge_enter()/drm_bridge_exit() resource protection was added,
the drm_bridge_exit() incidentally was always called, which is the correct
approach. But only because the early exit in sn65dsi83_reset_pipe() was
never hit because sn65dsi83_reset_pipe() always returns 0.

In order get back to a situation where enable_irq() is not called on
sn65dsi83_reset_pipe() failure, which should help protect against irq
storms, we need to reintroduce a non-zero return value from
sn65dsi83_reset_pipe() on error, and fix sn65dsi83_reset_work() so that we
always exit the DRM bridge critical section with drm_bridge_exit().

[1] commit e17fadff7ab9 ("drm/bridge: ti-sn65dsi83: Switch to drm_bridge_helper_reset_crtc")
[2] commit d2e8d1bc840b ("drm/bridge: ti-sn65dsi83: protect device resources on unplug")

Fixes: e17fadff7ab9 ("drm/bridge: ti-sn65dsi83: Switch to drm_bridge_helper_reset_crtc")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Esben Haabendal <esben@xxxxxxxxxx>
---
 drivers/gpu/drm/bridge/ti-sn65dsi83.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 42b451432bbb..9f530cd05d2f 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -403,7 +403,7 @@ static int sn65dsi83_reset_pipe(struct sn65dsi83 *sn65dsi83)
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
-	return 0;
+	return err;
 }
 
 static void sn65dsi83_reset_work(struct work_struct *ws)
@@ -419,11 +419,13 @@ static void sn65dsi83_reset_work(struct work_struct *ws)
 	ret = sn65dsi83_reset_pipe(ctx);
 	if (ret) {
 		dev_err(ctx->dev, "reset pipe failed %pe\n", ERR_PTR(ret));
-		return;
+		goto bridge_exit;
 	}
+
 	if (ctx->irq)
 		enable_irq(ctx->irq);
 
+bridge_exit:
 	drm_bridge_exit(idx);
 }
 

-- 
2.55.0