[PATCH] drm/tegra: dsi: Unconditionally manage reset line

[Mikko Perttunen <mperttunen@nvidia.com>]

The DSI driver ignores the reset line if a power domain is configured.
This was originally added to support Tegra210, where the power domain
provider has to control the reset line -- at that time, older SoCs
didn't have a power domain for DSI. Now, however, they do with the core
power domain.

This happens to work on most systems due to DSI already being out of
reset when booting the kernel, but on Tegra114 Dalmore, this is not the
case and causes the system to hang during boot.

Ownership of the reset line is no longer a problem with reset
acquire/release semantics, so control the DSI reset unconditionally
from the DSI driver (possibly in addition to the power domain driver).
The device tree bindings already require the reset and it is present
on all platforms, so this is safe to do.

Fixes: 4cc90d4c043e ("ARM: tegra: Configure Tegra114 power domains")
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
---
 drivers/gpu/drm/tegra/dsi.c | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
index cb88aafbd36f..7124cf648a1a 100644
--- a/drivers/gpu/drm/tegra/dsi.c
+++ b/drivers/gpu/drm/tegra/dsi.c
@@ -1113,14 +1113,14 @@ static int tegra_dsi_runtime_suspend(struct host1x_client *client)
 	struct device *dev = client->dev;
 	int err;
 
-	if (dsi->rst) {
-		err = reset_control_assert(dsi->rst);
-		if (err < 0) {
-			dev_err(dev, "failed to assert reset: %d\n", err);
-			return err;
-		}
+	err = reset_control_assert(dsi->rst);
+	if (err < 0) {
+		dev_err(dev, "failed to assert reset: %d\n", err);
+		return err;
 	}
 
+	reset_control_release(dsi->rst);
+
 	usleep_range(1000, 2000);
 
 	clk_disable_unprepare(dsi->clk_lp);
@@ -1164,16 +1164,22 @@ static int tegra_dsi_runtime_resume(struct host1x_client *client)
 
 	usleep_range(1000, 2000);
 
-	if (dsi->rst) {
-		err = reset_control_deassert(dsi->rst);
-		if (err < 0) {
-			dev_err(dev, "cannot assert reset: %d\n", err);
-			goto disable_clk_lp;
-		}
+	err = reset_control_acquire(dsi->rst);
+	if (err < 0) {
+		dev_err(dev, "failed to acquire reset: %d\n", err);
+		goto disable_clk_lp;
+	}
+
+	err = reset_control_deassert(dsi->rst);
+	if (err < 0) {
+		dev_err(dev, "cannot deassert reset: %d\n", err);
+		goto release_reset;
 	}
 
 	return 0;
 
+release_reset:
+	reset_control_release(dsi->rst);
 disable_clk_lp:
 	clk_disable_unprepare(dsi->clk_lp);
 disable_clk:
@@ -1623,12 +1629,10 @@ static int tegra_dsi_probe(struct platform_device *pdev)
 	dsi->format = MIPI_DSI_FMT_RGB888;
 	dsi->lanes = 4;
 
-	if (!pdev->dev.pm_domain) {
-		dsi->rst = devm_reset_control_get(&pdev->dev, "dsi");
-		if (IS_ERR(dsi->rst)) {
-			err = PTR_ERR(dsi->rst);
-			goto remove;
-		}
+	dsi->rst = devm_reset_control_get_exclusive_released(&pdev->dev, "dsi");
+	if (IS_ERR(dsi->rst)) {
+		err = PTR_ERR(dsi->rst);
+		goto remove;
 	}
 
 	dsi->clk = devm_clk_get(&pdev->dev, NULL);

---
base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
change-id: 20260930-dalmore-fixes-dsi-reset-4f3191dca886