[PATCH] drm/bridge: sii902x: Balance audio mclk enable and disable

[Sen Wang <sen@ti.com>]

The driver currently has an unbalanced clk enable count, as
sii902x_audio_hw_params() enables the mclk, but sii902x_audio_shutdown()
disables it unconditionally. This creates a few issues:

1. hdmi-codec calls audio_shutdown() on every PCM close, even if
   hw_params() never ran. For example, PipeWire queries the hw params
   at initialization, via:

     aplay -D hw:0,0 --dump-hw-params /dev/zero

   The clock core then hits WARN() in clk_core_disable() and
   clk_core_unprepare(), printing a backtrace and tainting the kernel:

     sii9022-mclk already disabled
     sii9022-mclk already unprepared

2. A second hw_params() without a shutdown in between enables the
   clock again, thus the count never returns to zero.

Therefore track whether hw_params() enabled the clock, and only disable
it in that case, to keep the clock enable count balanced.

Fixes: ff5781634c41 ("drm/bridge: sii902x: Implement HDMI audio support")
Signed-off-by: Sen Wang <sen@ti.com>
---
 drivers/gpu/drm/bridge/sii902x.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
index 9aac44ed5b67..df72712f4296 100644
--- a/drivers/gpu/drm/bridge/sii902x.c
+++ b/drivers/gpu/drm/bridge/sii902x.c
@@ -186,6 +186,7 @@ struct sii902x {
 	 */
 	struct mutex mutex;
 	struct sii902x_audio {
+		bool mclk_enabled;
 		struct platform_device *pdev;
 		struct clk *mclk;
 		u32 i2s_fifo_sequence[4];
@@ -681,10 +682,13 @@ static int sii902x_audio_hw_params(struct device *dev, void *data,
 		}
 	}
 
-	ret = clk_prepare_enable(sii902x->audio.mclk);
-	if (ret) {
-		dev_err(dev, "Enabling mclk failed: %d\n", ret);
-		return ret;
+	if (!sii902x->audio.mclk_enabled) {
+		ret = clk_prepare_enable(sii902x->audio.mclk);
+		if (ret) {
+			dev_err(dev, "Enabling mclk failed: %d\n", ret);
+			return ret;
+		}
+		sii902x->audio.mclk_enabled = true;
 	}
 
 	if (sii902x->audio.mclk) {
@@ -761,6 +765,7 @@ static int sii902x_audio_hw_params(struct device *dev, void *data,
 
 	if (ret) {
 		clk_disable_unprepare(sii902x->audio.mclk);
+		sii902x->audio.mclk_enabled = false;
 		dev_err(dev, "%s: hdmi audio enable failed: %d\n", __func__,
 			ret);
 	}
@@ -779,7 +784,10 @@ static void sii902x_audio_shutdown(struct device *dev, void *data)
 
 	mutex_unlock(&sii902x->mutex);
 
-	clk_disable_unprepare(sii902x->audio.mclk);
+	if (sii902x->audio.mclk_enabled) {
+		clk_disable_unprepare(sii902x->audio.mclk);
+		sii902x->audio.mclk_enabled = false;
+	}
 }
 
 static int sii902x_audio_mute(struct device *dev, void *data,
-- 
2.43.0