[PATCH v2] drm/bridge: parade-ps8640: Ensure bridge is suspended in .post_disable()

[Pin-yen Lin]

The ps8640 bridge seems to expect everything to be power cycled at the
disable process, but sometimes ps8640_aux_transfer() holds the runtime
PM reference and prevents the bridge from suspend.

Prevent that by introducing a mutex lock between ps8640_aux_transfer()
and .post_disable() to make sure the bridge is really powered off.

Fixes: 826cff3f7ebb ("drm/bridge: parade-ps8640: Enable runtime power 
management")
Signed-off-by: Pin-yen Lin <treapk...@chromium.org>
---

Changes in v2:
- Use mutex instead of the completion and autosuspend hack

 drivers/gpu/drm/bridge/parade-ps8640.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c 
b/drivers/gpu/drm/bridge/parade-ps8640.c
index 8161b1a1a4b1..46c84ce66041 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -107,6 +107,7 @@ struct ps8640 {
        struct device_link *link;
        bool pre_enabled;
        bool need_post_hpd_delay;
+       struct mutex aux_lock;
 };
 
 static const struct regmap_config ps8640_regmap_config[] = {
@@ -344,10 +345,12 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
        struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev;
        int ret;
 
+       mutex_lock(&ps_bridge->aux_lock);
        pm_runtime_get_sync(dev);
        ret = ps8640_aux_transfer_msg(aux, msg);
        pm_runtime_mark_last_busy(dev);
        pm_runtime_put_autosuspend(dev);
+       mutex_unlock(&ps_bridge->aux_lock);
 
        return ret;
 }
@@ -469,7 +472,18 @@ static void ps8640_atomic_post_disable(struct drm_bridge 
*bridge,
        ps_bridge->pre_enabled = false;
 
        ps8640_bridge_vdo_control(ps_bridge, DISABLE);
+
+       /*
+        * The bridge seems to expect everything to be power cycled at the
+        * disable process, so grab a lock here to make sure
+        * ps8640_aux_transfer() is not holding a runtime PM reference and
+        * preventing the bridge from suspend.
+        */
+       mutex_lock(&ps_bridge->aux_lock);
+
        pm_runtime_put_sync_suspend(&ps_bridge->page[PAGE0_DP_CNTL]->dev);
+
+       mutex_unlock(&ps_bridge->aux_lock);
 }
 
 static int ps8640_bridge_attach(struct drm_bridge *bridge,
@@ -618,6 +632,8 @@ static int ps8640_probe(struct i2c_client *client)
        if (!ps_bridge)
                return -ENOMEM;
 
+       mutex_init(&ps_bridge->aux_lock);
+
        ps_bridge->supplies[0].supply = "vdd12";
        ps_bridge->supplies[1].supply = "vdd33";
        ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ps_bridge->supplies),
-- 
2.43.0.472.g3155946c3a-goog