drm/tegra: sor - Protect CRC debugfs against enable state

Accessing the CRC debugfs file will hang the system if the SOR is not
enabled, so make sure that it is stays enabled until the CRC has been
read.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/sor.c

@@ -34,6 +34,7 @@ struct tegra_sor {
 
 	struct tegra_dpaux *dpaux;
 
+	struct mutex lock;
 	bool enabled;
 
 	struct dentry *debugfs;
@@ -299,14 +300,16 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 	unsigned int vbe, vse, hbe, hse, vbs, hbs, i;
 	struct tegra_sor *sor = to_sor(output);
 	unsigned long value;
-	int err;
+	int err = 0;
+
+	mutex_lock(&sor->lock);
 
 	if (sor->enabled)
-		return 0;
+		goto unlock;
 
 	err = clk_prepare_enable(sor->clk);
 	if (err < 0)
-		return err;
+		goto unlock;
 
 	reset_control_deassert(sor->rst);
 
@@ -388,7 +391,7 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 	err = tegra_io_rail_power_on(TEGRA_IO_RAIL_LVDS);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to power on I/O rail: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	usleep_range(5, 100);
@@ -512,21 +515,21 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 		if (err < 0) {
 			dev_err(sor->dev, "failed to probe eDP link: %d\n",
 				err);
-			return err;
+			goto unlock;
 		}
 
 		err = drm_dp_link_power_up(aux, &link);
 		if (err < 0) {
 			dev_err(sor->dev, "failed to power up eDP link: %d\n",
 				err);
-			return err;
+			goto unlock;
 		}
 
 		err = drm_dp_link_configure(aux, &link);
 		if (err < 0) {
 			dev_err(sor->dev, "failed to configure eDP link: %d\n",
 				err);
-			return err;
+			goto unlock;
 		}
 
 		rate = drm_dp_link_rate_to_bw_code(link.rate);
@@ -561,7 +564,7 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 		if (err < 0) {
 			dev_err(sor->dev, "DP fast link training failed: %d\n",
 				err);
-			return err;
+			goto unlock;
 		}
 
 		dev_dbg(sor->dev, "fast link training succeeded\n");
@@ -570,7 +573,7 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 	err = tegra_sor_power_up(sor, 250);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to power up SOR: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	/* start display controller in continuous mode */
@@ -635,7 +638,7 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 	err = tegra_sor_setup_pwm(sor, 250);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to setup PWM: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	value = tegra_dc_readl(dc, DC_DISP_DISP_WIN_OPTIONS);
@@ -647,18 +650,20 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 	err = tegra_sor_attach(sor);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to attach SOR: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	err = tegra_sor_wakeup(sor);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to enable DC: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	sor->enabled = true;
 
-	return 0;
+unlock:
+	mutex_unlock(&sor->lock);
+	return err;
 }
 
 static int tegra_sor_detach(struct tegra_sor *sor)
@@ -786,15 +791,17 @@ static int tegra_output_sor_disable(struct tegra_output *output)
 	struct tegra_dc *dc = to_tegra_dc(output->encoder.crtc);
 	struct tegra_sor *sor = to_sor(output);
 	unsigned long value;
-	int err;
+	int err = 0;
+
+	mutex_lock(&sor->lock);
 
 	if (!sor->enabled)
-		return 0;
+		goto unlock;
 
 	err = tegra_sor_detach(sor);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to detach SOR: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	tegra_sor_writel(sor, 0, SOR_STATE_1);
@@ -835,21 +842,21 @@ static int tegra_output_sor_disable(struct tegra_output *output)
 	err = tegra_sor_power_down(sor);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to power down SOR: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	if (sor->dpaux) {
 		err = tegra_dpaux_disable(sor->dpaux);
 		if (err < 0) {
 			dev_err(sor->dev, "failed to disable DP: %d\n", err);
-			return err;
+			goto unlock;
 		}
 	}
 
 	err = tegra_io_rail_power_off(TEGRA_IO_RAIL_LVDS);
 	if (err < 0) {
 		dev_err(sor->dev, "failed to power off I/O rail: %d\n", err);
-		return err;
+		goto unlock;
 	}
 
 	reset_control_assert(sor->rst);
@@ -857,7 +864,9 @@ static int tegra_output_sor_disable(struct tegra_output *output)
 
 	sor->enabled = false;
 
-	return 0;
+unlock:
+	mutex_unlock(&sor->lock);
+	return err;
 }
 
 static int tegra_output_sor_setup_clock(struct tegra_output *output,
@@ -952,10 +961,16 @@ static ssize_t tegra_sor_crc_read(struct file *file, char __user *buffer,
 				  size_t size, loff_t *ppos)
 {
 	struct tegra_sor *sor = file->private_data;
+	ssize_t num, err;
 	char buf[10];
-	ssize_t num;
 	u32 value;
-	int err;
+
+	mutex_lock(&sor->lock);
+
+	if (!sor->enabled) {
+		err = -EAGAIN;
+		goto unlock;
+	}
 
 	value = tegra_sor_readl(sor, SOR_STATE_1);
 	value &= ~SOR_STATE_ASY_CRC_MODE_MASK;
@@ -971,14 +986,18 @@ static ssize_t tegra_sor_crc_read(struct file *file, char __user *buffer,
 
 	err = tegra_sor_crc_wait(sor, 100);
 	if (err < 0)
-		return err;
+		goto unlock;
 
 	tegra_sor_writel(sor, SOR_CRC_A_RESET, SOR_CRC_A);
 	value = tegra_sor_readl(sor, SOR_CRC_B);
 
 	num = scnprintf(buf, sizeof(buf), "%08x\n", value);
 
-	return simple_read_from_buffer(buffer, size, ppos, buf, num);
+	err = simple_read_from_buffer(buffer, size, ppos, buf, num);
+
+unlock:
+	mutex_unlock(&sor->lock);
+	return err;
 }
 
 static const struct file_operations tegra_sor_crc_fops = {
@@ -1168,6 +1187,8 @@ static int tegra_sor_probe(struct platform_device *pdev)
 	sor->client.ops = &sor_client_ops;
 	sor->client.dev = &pdev->dev;
 
+	mutex_init(&sor->lock);
+
 	err = host1x_client_register(&sor->client);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to register host1x client: %d\n",