[PATCH v2 5/9] media: synopsys: hdmirx: give the signal lock wait a real timeout

[Sascha Hauer]

From: Gerald Loacker <gerald.loacker@xxxxxxxxxxxxxx>

hdmirx_wait_signal_lock() bounded itself by a count of 300 iterations.
How long that came to depended on the debounce inside
tx_5v_power_present(), which the loop calls once per iteration and which
sleeps about 7ms of it, so the effective timeout was around two seconds
by accident rather than by design.

That accident is about to go away. A later patch in this series takes the
5V state from an upstream subdev where the board has no hpd-gpios, which
leaves tx_5v_power_present() a plain read of a flag costing microseconds.
The same 300 iterations would then be over in a few milliseconds and the
wait would give up almost immediately.

Poll on a fixed 10ms interval against an explicit three second deadline.
Check the deadline after the 5V test so a disconnect is still reported as
-ENOLINK rather than a timeout, and report the timeout as -ETIMEDOUT; the
sole caller only tests for non-zero, so neither is a change in behaviour.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Gerald Loacker <gerald.loacker@xxxxxxxxxxxxxx>
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
 .../media/platform/synopsys/hdmirx/snps_hdmirx.c   | 40 +++++++++++++++-------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/drivers/media/platform/synopsys/hdmirx/snps_hdmirx.c b/drivers/media/platform/synopsys/hdmirx/snps_hdmirx.c
index d80143347fe0c..9af1e71afb4e5 100644
--- a/drivers/media/platform/synopsys/hdmirx/snps_hdmirx.c
+++ b/drivers/media/platform/synopsys/hdmirx/snps_hdmirx.c
@@ -2133,13 +2133,25 @@ static irqreturn_t hdmirx_dma_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+/*
+ * Wait for the HDMI signal to lock: TMDS clock detection and ratio
+ * configuration, then PHY and CMU lock, then DMA lock.
+ *
+ * The wait used to be bounded by a count of 300 iterations. What that came
+ * to in wall clock time was decided by the debounce inside
+ * tx_5v_power_present(), which is called once per iteration and sleeps
+ * about 7ms of it, so the real timeout was an accident of how 5V happens to
+ * be sensed. Poll on a fixed interval against an explicit deadline instead.
+ */
 static int hdmirx_wait_signal_lock(struct snps_hdmirx_dev *hdmirx_dev)
 {
 	struct v4l2_device *v4l2_dev = &hdmirx_dev->v4l2_dev;
 	u32 mu_status, scdc_status, dma_st10, cmu_st;
-	u32 i;
+	unsigned long timeout;
+
+	timeout = jiffies + msecs_to_jiffies(3000);
 
-	for (i = 0; i < 300; i++) {
+	for (;;) {
 		mu_status = hdmirx_readl(hdmirx_dev, MAINUNIT_STATUS);
 		scdc_status = hdmirx_readl(hdmirx_dev, SCDC_REGBANK_STATUS3);
 		dma_st10 = hdmirx_readl(hdmirx_dev, DMA_STATUS10);
@@ -2153,21 +2165,25 @@ static int hdmirx_wait_signal_lock(struct snps_hdmirx_dev *hdmirx_dev)
 		if (!tx_5v_power_present(hdmirx_dev)) {
 			v4l2_dbg(1, debug, v4l2_dev,
 				 "%s: HDMI pull out, return\n", __func__);
-			return -1;
+			return -ENOLINK;
 		}
 
-		hdmirx_tmds_clk_ratio_config(hdmirx_dev);
-	}
+		if (time_after(jiffies, timeout)) {
+			v4l2_err(v4l2_dev,
+				 "%s: signal not lock, tmds_clk_ratio:%d\n",
+				 __func__, hdmirx_dev->tmds_clk_ratio);
+			v4l2_err(v4l2_dev,
+				 "%s: mu_st:%#x, scdc_st:%#x, dma_st10:%#x, cmu_st:%#x\n",
+				 __func__, mu_status, scdc_status, dma_st10,
+				 cmu_st);
+			return -ETIMEDOUT;
+		}
 
-	if (i == 300) {
-		v4l2_err(v4l2_dev, "%s: signal not lock, tmds_clk_ratio:%d\n",
-			 __func__, hdmirx_dev->tmds_clk_ratio);
-		v4l2_err(v4l2_dev, "%s: mu_st:%#x, scdc_st:%#x, dma_st10:%#x\n",
-			 __func__, mu_status, scdc_status, dma_st10);
-		return -1;
+		hdmirx_tmds_clk_ratio_config(hdmirx_dev);
+		usleep_range(10000, 11000);
 	}
 
-	v4l2_dbg(1, debug, v4l2_dev, "%s: signal lock ok, i:%d\n", __func__, i);
+	v4l2_dbg(1, debug, v4l2_dev, "%s: signal lock ok\n", __func__);
 	hdmirx_writel(hdmirx_dev, GLOBAL_SWRESET_REQUEST, DATAPATH_SWRESETREQ);
 
 	reinit_completion(&hdmirx_dev->avi_pkt_rcv);

-- 
2.47.3