[PATCH 4.9 087/167] drm/bridge: analogix_dp: Grab runtime PM reference for DP-AUX

Greg Kroah-Hartman
2022-06-13T10:23:17Z

From: Brian Norris <briannorris@chromium.org>

commit 8fb6c44fe8468f92ac7b8bbfcca4404a4e88645f upstream.

If the display is not enable()d, then we aren't holding a runtime PM
reference here. Thus, it's easy to accidentally cause a hang, if user
space is poking around at /dev/drm_dp_aux0 at the "wrong" time.

Let's get a runtime PM reference, and check that we "see" the panel.
Don't force any panel power-up, etc., because that can be intrusive, and
that's not what other drivers do (see
drivers/gpu/drm/bridge/ti-sn65dsi86.c and
drivers/gpu/drm/bridge/parade-ps8640.c.)

Fixes: 0d97ad03f422 ("drm/bridge: analogix_dp: Remove duplicated code")
Cc: <stable@vger.kernel.org>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220301181107.v4.1.I773a08785666ebb236917b0c8e6c05e3de471e75@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1275,8 +1275,19 @@ static ssize_t analogix_dpaux_transfer(s
struct drm_dp_aux_msg *msg)
{
struct analogix_dp_device *dp = to_dp(aux);
+ int ret;

- return analogix_dp_transfer(dp, msg);
+ pm_runtime_get_sync(dp->dev);
+
+ ret = analogix_dp_detect_hpd(dp);
+ if (ret)
+ goto out;
+
+ ret = analogix_dp_transfer(dp, msg);
+out:
+ pm_runtime_put(dp->dev);
+
+ return ret;
}

int analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,