[PATCH v3 0/3] drm/bridge: sii9234: use extcon to detect cable attachment

[PATCH v3 0/3] drm/bridge: sii9234: use extcon to detect cable attachment

[Henrik Grimler]

Hi,

This series fixes so HDMI through the sii9234 MHL chip works when
cable is hotplugged, by making the MHL chip use extcon cable detection
functions. Patch 3, that actually implements the extcon parts, is heavily
inspired by commit 688838442147 ("drm/bridge/sii8620: use micro-USB
cable detection logic to detect MHL") by Maciej Purski.

Before these changes, HDMI only worked if cable was plugged in before
booting. If no cable was connected, then wlr-randr still showed HDMI
as connected, with 0x0 px, which confused at least some UIs (phosh)
and caused problems:
https://gitlab.gnome.org/World/Phosh/phosh/-/issues/828

Tested on exynos4412-i9305.

Best regards,
Henrik Grimler

Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
Changes in v3:

- Fix return of dev_err_probe in patch 2 and patch 3, spotted by
  Dmitry and Marek respectively.
- Change to depends on EXTCON || !EXTCON instead of select
- Collect tags for patch 1 (not 3 since there were (minor) changes)
- Link to v2: https://lore.kernel.org/r/20250724-exynos4-sii9234-driver-v2-0-faee244f1d40@grimler.se

Changes in v2:
- Add dependency on extcon in patch 3. Issue reported by kernel test robot <lkp@intel.com>
- Link to v1: https://lore.kernel.org/r/20250721-exynos4-sii9234-driver-v1-0-2e47ed02f677@grimler.se

---
Henrik Grimler (3):
      drm/bridge: sii9234: fix some typos in comments and messages
      drm/bridge: sii9234: use dev_err_probe where applicable
      drm/bridge: sii9234: use extcon cable detection logic to detect MHL

 drivers/gpu/drm/bridge/Kconfig   |   1 +
 drivers/gpu/drm/bridge/sii9234.c | 124 +++++++++++++++++++++++++++++++--------
 2 files changed, 102 insertions(+), 23 deletions(-)
---
base-commit: efe927b9702643a1d80472664c2642f0304cb608
change-id: 20231218-exynos4-sii9234-driver-d817d4b511d5

Best regards,
-- 
Henrik Grimler <henrik@grimler.se>

[PATCH v3 1/3] drm/bridge: sii9234: fix some typos in comments and messages

[Henrik Grimler]

Fix spelling and formatting so that the code is easier to follow, and
so that it is more searchable.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
v3: collect tags
v2: no changes
---
 drivers/gpu/drm/bridge/sii9234.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/sii9234.c b/drivers/gpu/drm/bridge/sii9234.c
index bb1bed03eb5b7ae67f752c0d593dc54131e9e370..930117bbba87285e62107389606897740516eb0a 100644
--- a/drivers/gpu/drm/bridge/sii9234.c
+++ b/drivers/gpu/drm/bridge/sii9234.c
@@ -339,7 +339,7 @@ static int sii9234_cbus_reset(struct sii9234 *ctx)
 	return sii9234_clear_error(ctx);
 }
 
-/* Require to chek mhl imformation of samsung in cbus_init_register */
+/* Require to check mhl information of samsung in cbus_init_register */
 static int sii9234_cbus_init(struct sii9234 *ctx)
 {
 	cbus_writeb(ctx, 0x07, 0xF2);
@@ -614,7 +614,7 @@ static void sii9234_cable_out(struct sii9234 *ctx)
 
 	disable_irq(to_i2c_client(ctx->dev)->irq);
 	tpi_writeb(ctx, TPI_DPD_REG, 0);
-	/* Turn on&off hpd festure for only QCT HDMI */
+	/* Turn on&off hpd feature for only QCT HDMI */
 	sii9234_hw_off(ctx);
 
 	ctx->state = ST_OFF;
@@ -708,7 +708,7 @@ static enum sii9234_state sii9234_rsen_change(struct sii9234 *ctx)
 {
 	int value;
 
-	/* Work_around code to handle wrong interrupt */
+	/* Workaround code to handle wrong interrupt */
 	if (ctx->state != ST_RGND_1K) {
 		dev_err(ctx->dev, "RSEN_HIGH without RGND_1K\n");
 		return ST_FAILURE;
@@ -723,9 +723,9 @@ static enum sii9234_state sii9234_rsen_change(struct sii9234 *ctx)
 	}
 	dev_dbg(ctx->dev, "RSEN lost\n");
 	/*
-	 * Once RSEN loss is confirmed,we need to check
-	 * based on cable status and chip power status,whether
-	 * it is SINK Loss(HDMI cable not connected, TV Off)
+	 * Once RSEN loss is confirmed, we need to check
+	 * based on cable status and chip power status, whether
+	 * it is SINK Loss (HDMI cable not connected, TV Off)
 	 * or MHL cable disconnection
 	 * TODO: Define the below mhl_disconnection()
 	 */
@@ -820,7 +820,7 @@ static int sii9234_init_resources(struct sii9234 *ctx,
 	int ret;
 
 	if (!ctx->dev->of_node) {
-		dev_err(ctx->dev, "not DT device\n");
+		dev_err(ctx->dev, "no DT device\n");
 		return -ENODEV;
 	}
 

-- 
2.50.1

[PATCH v3 2/3] drm/bridge: sii9234: use dev_err_probe where applicable

[Henrik Grimler]

In case of error during resource acquisition the driver should print
an error message only if it is not deferred probe. Use dev_err_probe
helper to handle this, which will also record defer probe reason for
debugging.

Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
v3: add missing return in error path, spotted by Dmitry
v2: no changes
---
 drivers/gpu/drm/bridge/sii9234.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/bridge/sii9234.c b/drivers/gpu/drm/bridge/sii9234.c
index 930117bbba87285e62107389606897740516eb0a..e43248e515b3dcdde043997288d61f738417b8f0 100644
--- a/drivers/gpu/drm/bridge/sii9234.c
+++ b/drivers/gpu/drm/bridge/sii9234.c
@@ -825,21 +825,17 @@ static int sii9234_init_resources(struct sii9234 *ctx,
 	}
 
 	ctx->gpio_reset = devm_gpiod_get(ctx->dev, "reset", GPIOD_OUT_LOW);
-	if (IS_ERR(ctx->gpio_reset)) {
-		dev_err(ctx->dev, "failed to get reset gpio from DT\n");
-		return PTR_ERR(ctx->gpio_reset);
-	}
+	if (IS_ERR(ctx->gpio_reset))
+		return dev_err_probe(ctx->dev, PTR_ERR(ctx->gpio_reset),
+				     "failed to get reset gpio from DT\n");
 
 	ctx->supplies[0].supply = "avcc12";
 	ctx->supplies[1].supply = "avcc33";
 	ctx->supplies[2].supply = "iovcc18";
 	ctx->supplies[3].supply = "cvcc12";
 	ret = devm_regulator_bulk_get(ctx->dev, 4, ctx->supplies);
-	if (ret) {
-		if (ret != -EPROBE_DEFER)
-			dev_err(ctx->dev, "regulator_bulk failed\n");
-		return ret;
-	}
+	if (ret)
+		return dev_err_probe(ctx->dev, ret, "regulator_bulk failed\n");
 
 	ctx->client[I2C_MHL] = client;
 
@@ -911,10 +907,9 @@ static int sii9234_probe(struct i2c_client *client)
 					sii9234_irq_thread,
 					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
 					"sii9234", ctx);
-	if (ret < 0) {
-		dev_err(dev, "failed to install IRQ handler\n");
-		return ret;
-	}
+	if (ret < 0)
+		return dev_err_probe(dev, ret,
+				     "failed to install IRQ handler\n");
 
 	ret = sii9234_init_resources(ctx, client);
 	if (ret < 0)

-- 
2.50.1

Re: [PATCH v3 2/3] drm/bridge: sii9234: use dev_err_probe where applicable

[Dmitry Baryshkov]

On Sun, Aug 24, 2025 at 01:16:55PM +0200, Henrik Grimler wrote:
> In case of error during resource acquisition the driver should print
> an error message only if it is not deferred probe. Use dev_err_probe
> helper to handle this, which will also record defer probe reason for
> debugging.
> 
> Signed-off-by: Henrik Grimler <henrik@grimler.se>
> ---
> v3: add missing return in error path, spotted by Dmitry
> v2: no changes
> ---
>  drivers/gpu/drm/bridge/sii9234.c | 21 ++++++++-------------
>  1 file changed, 8 insertions(+), 13 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>


-- 
With best wishes
Dmitry

[PATCH v3 3/3] drm/bridge: sii9234: use extcon cable detection logic to detect MHL

[Henrik Grimler]

To use MHL we currently need the MHL chip to be permanently on, which
consumes unnecessary power. Let's use extcon attached to MUIC to enable
the MHL chip only if it detects an MHL cable.

Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
v3: add missing return in error path, spotted by Marek
    Use depends on EXTCON || !EXTCON instead of select
v2: add dependency on extcon. Issue reported by kernel test robot
    <lkp@intel.com>
---
 drivers/gpu/drm/bridge/Kconfig   |  1 +
 drivers/gpu/drm/bridge/sii9234.c | 89 ++++++++++++++++++++++++++++++++++++++--
 2 files changed, 87 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 6945029b35929a8e30054ac1a699bd88ab0487f2..bf73f8d900ebd8da9fa3444c0b2d9bfc901ea773 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -304,6 +304,7 @@ config DRM_SII902X
 config DRM_SII9234
 	tristate "Silicon Image SII9234 HDMI/MHL bridge"
 	depends on OF
+	depends on EXTCON || !EXTCON
 	help
 	  Say Y here if you want support for the MHL interface.
 	  It is an I2C driver, that detects connection of MHL bridge
diff --git a/drivers/gpu/drm/bridge/sii9234.c b/drivers/gpu/drm/bridge/sii9234.c
index e43248e515b3dcdde043997288d61f738417b8f0..72c6aeed6e12e43df3b052dadc0990f1609253f0 100644
--- a/drivers/gpu/drm/bridge/sii9234.c
+++ b/drivers/gpu/drm/bridge/sii9234.c
@@ -19,6 +19,7 @@
 
 #include <linux/delay.h>
 #include <linux/err.h>
+#include <linux/extcon.h>
 #include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
@@ -26,6 +27,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/of_graph.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 
@@ -170,8 +172,12 @@ struct sii9234 {
 	struct drm_bridge bridge;
 	struct device *dev;
 	struct gpio_desc *gpio_reset;
-	int i2c_error;
 	struct regulator_bulk_data supplies[4];
+	struct extcon_dev *extcon;
+	struct notifier_block extcon_nb;
+	struct work_struct extcon_wq;
+	int cable_state;
+	int i2c_error;
 
 	struct mutex lock; /* Protects fields below and device registers */
 	enum sii9234_state state;
@@ -863,6 +869,70 @@ static int sii9234_init_resources(struct sii9234 *ctx,
 	return 0;
 }
 
+static void sii9234_extcon_work(struct work_struct *work)
+{
+	struct sii9234 *ctx =
+		container_of(work, struct sii9234, extcon_wq);
+	int state = extcon_get_state(ctx->extcon, EXTCON_DISP_MHL);
+
+	if (state == ctx->cable_state)
+		return;
+
+	ctx->cable_state = state;
+
+	if (state > 0)
+		sii9234_cable_in(ctx);
+	else
+		sii9234_cable_out(ctx);
+}
+
+static int sii9234_extcon_notifier(struct notifier_block *self,
+			unsigned long event, void *ptr)
+{
+	struct sii9234 *ctx =
+		container_of(self, struct sii9234, extcon_nb);
+
+	schedule_work(&ctx->extcon_wq);
+
+	return NOTIFY_DONE;
+}
+
+static int sii9234_extcon_init(struct sii9234 *ctx)
+{
+	struct extcon_dev *edev;
+	struct device_node *musb, *muic;
+	int ret;
+
+	/* Get micro-USB connector node */
+	musb = of_graph_get_remote_node(ctx->dev->of_node, 1, -1);
+	/* Then get micro-USB Interface Controller node */
+	muic = of_get_next_parent(musb);
+
+	if (!muic) {
+		dev_info(ctx->dev,
+			 "no extcon found, switching to 'always on' mode\n");
+		return 0;
+	}
+
+	edev = extcon_find_edev_by_node(muic);
+	of_node_put(muic);
+	if (IS_ERR(edev)) {
+		return dev_err_probe(ctx->dev, PTR_ERR(edev),
+			      "invalid or missing extcon\n");
+	}
+
+	ctx->extcon = edev;
+	ctx->extcon_nb.notifier_call = sii9234_extcon_notifier;
+	INIT_WORK(&ctx->extcon_wq, sii9234_extcon_work);
+	ret = extcon_register_notifier(edev, EXTCON_DISP_MHL, &ctx->extcon_nb);
+	if (ret) {
+		dev_err(ctx->dev, "failed to register notifier for MHL\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 static enum drm_mode_status sii9234_mode_valid(struct drm_bridge *bridge,
 					 const struct drm_display_info *info,
 					 const struct drm_display_mode *mode)
@@ -915,12 +985,17 @@ static int sii9234_probe(struct i2c_client *client)
 	if (ret < 0)
 		return ret;
 
+	ret = sii9234_extcon_init(ctx);
+	if (ret < 0)
+		return ret;
+
 	i2c_set_clientdata(client, ctx);
 
 	ctx->bridge.of_node = dev->of_node;
 	drm_bridge_add(&ctx->bridge);
 
-	sii9234_cable_in(ctx);
+	if (!ctx->extcon)
+		sii9234_cable_in(ctx);
 
 	return 0;
 }
@@ -929,7 +1004,15 @@ static void sii9234_remove(struct i2c_client *client)
 {
 	struct sii9234 *ctx = i2c_get_clientdata(client);
 
-	sii9234_cable_out(ctx);
+	if (ctx->extcon) {
+		extcon_unregister_notifier(ctx->extcon, EXTCON_DISP_MHL,
+					   &ctx->extcon_nb);
+		flush_work(&ctx->extcon_wq);
+		if (ctx->cable_state > 0)
+			sii9234_cable_out(ctx);
+	} else {
+		sii9234_cable_out(ctx);
+	}
 	drm_bridge_remove(&ctx->bridge);
 }
 

-- 
2.50.1

Re: [PATCH v3 3/3] drm/bridge: sii9234: use extcon cable detection logic to detect MHL

[Marek Szyprowski]

On 24.08.2025 13:16, Henrik Grimler wrote:
> To use MHL we currently need the MHL chip to be permanently on, which
> consumes unnecessary power. Let's use extcon attached to MUIC to enable
> the MHL chip only if it detects an MHL cable.
>
> Signed-off-by: Henrik Grimler <henrik@grimler.se>

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

On Trats2 board the status of HDMI connector is no properly reported as 
disconnected when no cable is attached.

> ---
> v3: add missing return in error path, spotted by Marek
>      Use depends on EXTCON || !EXTCON instead of select
> v2: add dependency on extcon. Issue reported by kernel test robot
>      <lkp@intel.com>
> ---
>   drivers/gpu/drm/bridge/Kconfig   |  1 +
>   drivers/gpu/drm/bridge/sii9234.c | 89 ++++++++++++++++++++++++++++++++++++++--
>   2 files changed, 87 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 6945029b35929a8e30054ac1a699bd88ab0487f2..bf73f8d900ebd8da9fa3444c0b2d9bfc901ea773 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -304,6 +304,7 @@ config DRM_SII902X
>   config DRM_SII9234
>   	tristate "Silicon Image SII9234 HDMI/MHL bridge"
>   	depends on OF
> +	depends on EXTCON || !EXTCON
>   	help
>   	  Say Y here if you want support for the MHL interface.
>   	  It is an I2C driver, that detects connection of MHL bridge
> diff --git a/drivers/gpu/drm/bridge/sii9234.c b/drivers/gpu/drm/bridge/sii9234.c
> index e43248e515b3dcdde043997288d61f738417b8f0..72c6aeed6e12e43df3b052dadc0990f1609253f0 100644
> --- a/drivers/gpu/drm/bridge/sii9234.c
> +++ b/drivers/gpu/drm/bridge/sii9234.c
> @@ -19,6 +19,7 @@
>   
>   #include <linux/delay.h>
>   #include <linux/err.h>
> +#include <linux/extcon.h>
>   #include <linux/gpio/consumer.h>
>   #include <linux/i2c.h>
>   #include <linux/interrupt.h>
> @@ -26,6 +27,7 @@
>   #include <linux/kernel.h>
>   #include <linux/module.h>
>   #include <linux/mutex.h>
> +#include <linux/of_graph.h>
>   #include <linux/regulator/consumer.h>
>   #include <linux/slab.h>
>   
> @@ -170,8 +172,12 @@ struct sii9234 {
>   	struct drm_bridge bridge;
>   	struct device *dev;
>   	struct gpio_desc *gpio_reset;
> -	int i2c_error;
>   	struct regulator_bulk_data supplies[4];
> +	struct extcon_dev *extcon;
> +	struct notifier_block extcon_nb;
> +	struct work_struct extcon_wq;
> +	int cable_state;
> +	int i2c_error;
>   
>   	struct mutex lock; /* Protects fields below and device registers */
>   	enum sii9234_state state;
> @@ -863,6 +869,70 @@ static int sii9234_init_resources(struct sii9234 *ctx,
>   	return 0;
>   }
>   
> +static void sii9234_extcon_work(struct work_struct *work)
> +{
> +	struct sii9234 *ctx =
> +		container_of(work, struct sii9234, extcon_wq);
> +	int state = extcon_get_state(ctx->extcon, EXTCON_DISP_MHL);
> +
> +	if (state == ctx->cable_state)
> +		return;
> +
> +	ctx->cable_state = state;
> +
> +	if (state > 0)
> +		sii9234_cable_in(ctx);
> +	else
> +		sii9234_cable_out(ctx);
> +}
> +
> +static int sii9234_extcon_notifier(struct notifier_block *self,
> +			unsigned long event, void *ptr)
> +{
> +	struct sii9234 *ctx =
> +		container_of(self, struct sii9234, extcon_nb);
> +
> +	schedule_work(&ctx->extcon_wq);
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int sii9234_extcon_init(struct sii9234 *ctx)
> +{
> +	struct extcon_dev *edev;
> +	struct device_node *musb, *muic;
> +	int ret;
> +
> +	/* Get micro-USB connector node */
> +	musb = of_graph_get_remote_node(ctx->dev->of_node, 1, -1);
> +	/* Then get micro-USB Interface Controller node */
> +	muic = of_get_next_parent(musb);
> +
> +	if (!muic) {
> +		dev_info(ctx->dev,
> +			 "no extcon found, switching to 'always on' mode\n");
> +		return 0;
> +	}
> +
> +	edev = extcon_find_edev_by_node(muic);
> +	of_node_put(muic);
> +	if (IS_ERR(edev)) {
> +		return dev_err_probe(ctx->dev, PTR_ERR(edev),
> +			      "invalid or missing extcon\n");
> +	}
> +
> +	ctx->extcon = edev;
> +	ctx->extcon_nb.notifier_call = sii9234_extcon_notifier;
> +	INIT_WORK(&ctx->extcon_wq, sii9234_extcon_work);
> +	ret = extcon_register_notifier(edev, EXTCON_DISP_MHL, &ctx->extcon_nb);
> +	if (ret) {
> +		dev_err(ctx->dev, "failed to register notifier for MHL\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>   static enum drm_mode_status sii9234_mode_valid(struct drm_bridge *bridge,
>   					 const struct drm_display_info *info,
>   					 const struct drm_display_mode *mode)
> @@ -915,12 +985,17 @@ static int sii9234_probe(struct i2c_client *client)
>   	if (ret < 0)
>   		return ret;
>   
> +	ret = sii9234_extcon_init(ctx);
> +	if (ret < 0)
> +		return ret;
> +
>   	i2c_set_clientdata(client, ctx);
>   
>   	ctx->bridge.of_node = dev->of_node;
>   	drm_bridge_add(&ctx->bridge);
>   
> -	sii9234_cable_in(ctx);
> +	if (!ctx->extcon)
> +		sii9234_cable_in(ctx);
>   
>   	return 0;
>   }
> @@ -929,7 +1004,15 @@ static void sii9234_remove(struct i2c_client *client)
>   {
>   	struct sii9234 *ctx = i2c_get_clientdata(client);
>   
> -	sii9234_cable_out(ctx);
> +	if (ctx->extcon) {
> +		extcon_unregister_notifier(ctx->extcon, EXTCON_DISP_MHL,
> +					   &ctx->extcon_nb);
> +		flush_work(&ctx->extcon_wq);
> +		if (ctx->cable_state > 0)
> +			sii9234_cable_out(ctx);
> +	} else {
> +		sii9234_cable_out(ctx);
> +	}
>   	drm_bridge_remove(&ctx->bridge);
>   }
>   
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v3 3/3] drm/bridge: sii9234: use extcon cable detection logic to detect MHL

[Henrik Grimler]

Hi Marek,

On Mon, Aug 25, 2025 at 04:16:50PM +0200, Marek Szyprowski wrote:
> On 24.08.2025 13:16, Henrik Grimler wrote:
> > To use MHL we currently need the MHL chip to be permanently on, which
> > consumes unnecessary power. Let's use extcon attached to MUIC to enable
> > the MHL chip only if it detects an MHL cable.
> >
> > Signed-off-by: Henrik Grimler <henrik@grimler.se>
> 
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> 
> On Trats2 board the status of HDMI connector is no properly reported as 
> disconnected when no cable is attached.

Thanks for testing (again)!

In what way is it not properly reported as disconnected, are you
checking some sysfs property, or with some userspace tool?

If cable is connected and then disconnected, is status then correctly
reported?

Best regards,
Henrik Grimler

> > ---
> > v3: add missing return in error path, spotted by Marek
> >      Use depends on EXTCON || !EXTCON instead of select
> > v2: add dependency on extcon. Issue reported by kernel test robot
> >      <lkp@intel.com>
> > ---
> >   drivers/gpu/drm/bridge/Kconfig   |  1 +
> >   drivers/gpu/drm/bridge/sii9234.c | 89 ++++++++++++++++++++++++++++++++++++++--
> >   2 files changed, 87 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index 6945029b35929a8e30054ac1a699bd88ab0487f2..bf73f8d900ebd8da9fa3444c0b2d9bfc901ea773 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -304,6 +304,7 @@ config DRM_SII902X
> >   config DRM_SII9234
> >   	tristate "Silicon Image SII9234 HDMI/MHL bridge"
> >   	depends on OF
> > +	depends on EXTCON || !EXTCON
> >   	help
> >   	  Say Y here if you want support for the MHL interface.
> >   	  It is an I2C driver, that detects connection of MHL bridge
> > diff --git a/drivers/gpu/drm/bridge/sii9234.c b/drivers/gpu/drm/bridge/sii9234.c
> > index e43248e515b3dcdde043997288d61f738417b8f0..72c6aeed6e12e43df3b052dadc0990f1609253f0 100644
> > --- a/drivers/gpu/drm/bridge/sii9234.c
> > +++ b/drivers/gpu/drm/bridge/sii9234.c
> > @@ -19,6 +19,7 @@
> >   
> >   #include <linux/delay.h>
> >   #include <linux/err.h>
> > +#include <linux/extcon.h>
> >   #include <linux/gpio/consumer.h>
> >   #include <linux/i2c.h>
> >   #include <linux/interrupt.h>
> > @@ -26,6 +27,7 @@
> >   #include <linux/kernel.h>
> >   #include <linux/module.h>
> >   #include <linux/mutex.h>
> > +#include <linux/of_graph.h>
> >   #include <linux/regulator/consumer.h>
> >   #include <linux/slab.h>
> >   
> > @@ -170,8 +172,12 @@ struct sii9234 {
> >   	struct drm_bridge bridge;
> >   	struct device *dev;
> >   	struct gpio_desc *gpio_reset;
> > -	int i2c_error;
> >   	struct regulator_bulk_data supplies[4];
> > +	struct extcon_dev *extcon;
> > +	struct notifier_block extcon_nb;
> > +	struct work_struct extcon_wq;
> > +	int cable_state;
> > +	int i2c_error;
> >   
> >   	struct mutex lock; /* Protects fields below and device registers */
> >   	enum sii9234_state state;
> > @@ -863,6 +869,70 @@ static int sii9234_init_resources(struct sii9234 *ctx,
> >   	return 0;
> >   }
> >   
> > +static void sii9234_extcon_work(struct work_struct *work)
> > +{
> > +	struct sii9234 *ctx =
> > +		container_of(work, struct sii9234, extcon_wq);
> > +	int state = extcon_get_state(ctx->extcon, EXTCON_DISP_MHL);
> > +
> > +	if (state == ctx->cable_state)
> > +		return;
> > +
> > +	ctx->cable_state = state;
> > +
> > +	if (state > 0)
> > +		sii9234_cable_in(ctx);
> > +	else
> > +		sii9234_cable_out(ctx);
> > +}
> > +
> > +static int sii9234_extcon_notifier(struct notifier_block *self,
> > +			unsigned long event, void *ptr)
> > +{
> > +	struct sii9234 *ctx =
> > +		container_of(self, struct sii9234, extcon_nb);
> > +
> > +	schedule_work(&ctx->extcon_wq);
> > +
> > +	return NOTIFY_DONE;
> > +}
> > +
> > +static int sii9234_extcon_init(struct sii9234 *ctx)
> > +{
> > +	struct extcon_dev *edev;
> > +	struct device_node *musb, *muic;
> > +	int ret;
> > +
> > +	/* Get micro-USB connector node */
> > +	musb = of_graph_get_remote_node(ctx->dev->of_node, 1, -1);
> > +	/* Then get micro-USB Interface Controller node */
> > +	muic = of_get_next_parent(musb);
> > +
> > +	if (!muic) {
> > +		dev_info(ctx->dev,
> > +			 "no extcon found, switching to 'always on' mode\n");
> > +		return 0;
> > +	}
> > +
> > +	edev = extcon_find_edev_by_node(muic);
> > +	of_node_put(muic);
> > +	if (IS_ERR(edev)) {
> > +		return dev_err_probe(ctx->dev, PTR_ERR(edev),
> > +			      "invalid or missing extcon\n");
> > +	}
> > +
> > +	ctx->extcon = edev;
> > +	ctx->extcon_nb.notifier_call = sii9234_extcon_notifier;
> > +	INIT_WORK(&ctx->extcon_wq, sii9234_extcon_work);
> > +	ret = extcon_register_notifier(edev, EXTCON_DISP_MHL, &ctx->extcon_nb);
> > +	if (ret) {
> > +		dev_err(ctx->dev, "failed to register notifier for MHL\n");
> > +		return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >   static enum drm_mode_status sii9234_mode_valid(struct drm_bridge *bridge,
> >   					 const struct drm_display_info *info,
> >   					 const struct drm_display_mode *mode)
> > @@ -915,12 +985,17 @@ static int sii9234_probe(struct i2c_client *client)
> >   	if (ret < 0)
> >   		return ret;
> >   
> > +	ret = sii9234_extcon_init(ctx);
> > +	if (ret < 0)
> > +		return ret;
> > +
> >   	i2c_set_clientdata(client, ctx);
> >   
> >   	ctx->bridge.of_node = dev->of_node;
> >   	drm_bridge_add(&ctx->bridge);
> >   
> > -	sii9234_cable_in(ctx);
> > +	if (!ctx->extcon)
> > +		sii9234_cable_in(ctx);
> >   
> >   	return 0;
> >   }
> > @@ -929,7 +1004,15 @@ static void sii9234_remove(struct i2c_client *client)
> >   {
> >   	struct sii9234 *ctx = i2c_get_clientdata(client);
> >   
> > -	sii9234_cable_out(ctx);
> > +	if (ctx->extcon) {
> > +		extcon_unregister_notifier(ctx->extcon, EXTCON_DISP_MHL,
> > +					   &ctx->extcon_nb);
> > +		flush_work(&ctx->extcon_wq);
> > +		if (ctx->cable_state > 0)
> > +			sii9234_cable_out(ctx);
> > +	} else {
> > +		sii9234_cable_out(ctx);
> > +	}
> >   	drm_bridge_remove(&ctx->bridge);
> >   }
> >   
> >
> Best regards
> -- 
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
> 

Re: [PATCH v3 3/3] drm/bridge: sii9234: use extcon cable detection logic to detect MHL

[Marek Szyprowski]

On 03.09.2025 21:32, Henrik Grimler wrote:
> On Mon, Aug 25, 2025 at 04:16:50PM +0200, Marek Szyprowski wrote:
>> On 24.08.2025 13:16, Henrik Grimler wrote:
>>> To use MHL we currently need the MHL chip to be permanently on, which
>>> consumes unnecessary power. Let's use extcon attached to MUIC to enable
>>> the MHL chip only if it detects an MHL cable.
>>>
>>> Signed-off-by: Henrik Grimler <henrik@grimler.se>
>> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>
>> On Trats2 board the status of HDMI connector is no properly reported as
>> disconnected when no cable is attached.
> Thanks for testing (again)!
>
> In what way is it not properly reported as disconnected, are you
> checking some sysfs property, or with some userspace tool?

Huh, my typo. It should be 'connector is *now* properly reported', 
that's why I gave my 'tested-by' tag.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v3 3/3] drm/bridge: sii9234: use extcon cable detection logic to detect MHL

[Henrik Grimler]

Hi Marek,

On Thu, 2025-09-04 at 08:40 +0200, Marek Szyprowski wrote:
> On 03.09.2025 21:32, Henrik Grimler wrote:
> > On Mon, Aug 25, 2025 at 04:16:50PM +0200, Marek Szyprowski wrote:
> > > On 24.08.2025 13:16, Henrik Grimler wrote:
> > > > To use MHL we currently need the MHL chip to be permanently on,
> > > > which
> > > > consumes unnecessary power. Let's use extcon attached to MUIC
> > > > to enable
> > > > the MHL chip only if it detects an MHL cable.
> > > > 
> > > > Signed-off-by: Henrik Grimler <henrik@grimler.se>
> > > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > 
> > > On Trats2 board the status of HDMI connector is no properly
> > > reported as
> > > disconnected when no cable is attached.
> > Thanks for testing (again)!
> > 
> > In what way is it not properly reported as disconnected, are you
> > checking some sysfs property, or with some userspace tool?
> 
> Huh, my typo. It should be 'connector is *now* properly reported', 
> that's why I gave my 'tested-by' tag.

That clears it up, thank you :)

Best regards,
Henrik Grimler