[PATCH 2/2] drm/bridge: ti-sn65dsi83: protect device resources on unplug

Luca Ceresoli
2025-08-08T13:53:00Z

To support hot-unplug of this bridge we need to protect access to device
resources in case sn65dsi83_remove() happens concurrently to other code.

Some care is needed for the case when the unplug happens before
sn65dsi83_atomic_disable() has a chance to enter the critical section
(i.e. a successful drm_bridge_enter() call), which occurs whenever the
hardware is removed while the display is active. When that happens,
sn65dsi83_atomic_disable() in unable to release some resources, thus this
needs to be done in sn65dsi83_remove() after drm_bridge_unplug().

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
drivers/gpu/drm/bridge/ti-sn65dsi83.c | 53 +++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 033c44326552ab167d4e8d9b74957c585e4c6fb7..9e4cecf4f7cb056f0c34e87007fcebf50780e49c 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -157,6 +157,7 @@ struct sn65dsi83 {
struct drm_bridge *panel_bridge;
struct gpio_desc *enable_gpio;
struct regulator *vcc;
+ bool disable_resources_needed;
bool lvds_dual_link;
bool lvds_dual_link_even_odd_swap;
int lvds_vod_swing_conf[2];
@@ -406,6 +407,10 @@ static void sn65dsi83_reset_work(struct work_struct *ws)
{
struct sn65dsi83 *ctx = container_of(ws, struct sn65dsi83, reset_work);
int ret;
+ int idx;
+
+ if (!drm_bridge_enter(&ctx->bridge, &idx))
+ return;

/* Reset the pipe */
ret = sn65dsi83_reset_pipe(ctx);
@@ -415,12 +420,18 @@ static void sn65dsi83_reset_work(struct work_struct *ws)
}
if (ctx->irq)
enable_irq(ctx->irq);
+
+ drm_bridge_exit(idx);
}

static void sn65dsi83_handle_errors(struct sn65dsi83 *ctx)
{
unsigned int irq_stat;
int ret;
+ int idx;
+
+ if (!drm_bridge_enter(&ctx->bridge, &idx))
+ return;

/*
* Schedule a reset in case of:
@@ -441,6 +452,8 @@ static void sn65dsi83_handle_errors(struct sn65dsi83 *ctx)

schedule_work(&ctx->reset_work);
}
+
+ drm_bridge_exit(idx);
}

static void sn65dsi83_monitor_work(struct work_struct *work)
@@ -478,10 +491,15 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
__le16 le16val;
u16 val;
int ret;
+ int idx;
+
+ if (!drm_bridge_enter(bridge, &idx))
+ return;

ret = regulator_enable(ctx->vcc);
if (ret) {
dev_err(ctx->dev, "Failed to enable vcc: %d\n", ret);
+ drm_bridge_exit(idx);
return;
}

@@ -625,6 +643,8 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
dev_err(ctx->dev, "failed to lock PLL, ret=%i\n", ret);
/* On failure, disable PLL again and exit. */
regmap_write(ctx->regmap, REG_RC_PLL_EN, 0x00);
+ ctx->disable_resources_needed = true;
+ drm_bridge_exit(idx);
return;
}

@@ -633,6 +653,9 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,

/* Wait for 10ms after soft reset as specified in datasheet */
usleep_range(10000, 12000);
+
+ ctx->disable_resources_needed = true;
+ drm_bridge_exit(idx);
}

static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
@@ -640,6 +663,10 @@ static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
{
struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
unsigned int pval;
+ int idx;
+
+ if (!drm_bridge_enter(bridge, &idx))
+ return;

/* Clear all errors that got asserted during initialization. */
regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);
@@ -659,6 +686,8 @@ static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
/* Use the polling task */
sn65dsi83_monitor_start(ctx);
}
+
+ drm_bridge_exit(idx);
}

static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
@@ -666,6 +695,10 @@ static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
{
struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
int ret;
+ int idx;
+
+ if (!drm_bridge_enter(bridge, &idx))
+ return;

if (ctx->irq) {
/* Disable irq */
@@ -685,6 +718,9 @@ static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
dev_err(ctx->dev, "Failed to disable vcc: %d\n", ret);

regcache_mark_dirty(ctx->regmap);
+
+ ctx->disable_resources_needed = false;
+ drm_bridge_exit(idx);
}

static enum drm_mode_status
@@ -1005,7 +1041,24 @@ static void sn65dsi83_remove(struct i2c_client *client)
{
struct sn65dsi83 *ctx = i2c_get_clientdata(client);

+ drm_bridge_unplug(&ctx->bridge);
drm_bridge_remove(&ctx->bridge);
+
+ /*
+ * sn65dsi83_atomic_disable() should release some resources, but it
+ * cannot if we call drm_bridge_unplug() before it can
+ * drm_bridge_enter(). If that happens, let's release those
+ * resources now.
+ */
+ if (ctx->disable_resources_needed) {
+ if (!ctx->irq)
+ sn65dsi83_monitor_stop(ctx);
+
+ gpiod_set_value_cansleep(ctx->enable_gpio, 0);
+ usleep_range(10000, 11000);
+
+ regulator_disable(ctx->vcc);
+ }
}

static const struct i2c_device_id sn65dsi83_id[] = {

--
2.50.1