[PATCH RESEND v4 0/3] drm/bridge: sii9234: use extcon to detect cable attachment

[PATCH RESEND v4 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 v4:
- Collect tags
- Link to v3: https://lore.kernel.org/r/20250824-exynos4-sii9234-driver-v3-0-80849e716a37@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: a87fef0880c4f52769b5a3c2fc1b2d73aaa04eb3
change-id: 20231218-exynos4-sii9234-driver-d817d4b511d5

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

[PATCH RESEND v4 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>
---
v4: no changes
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 bb1bed03eb5b..930117bbba87 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;
 	}
 

-- 
2.54.0

[PATCH RESEND v4 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.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
v4: collect tags
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 930117bbba87..e43248e515b3 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)

-- 
2.54.0

[PATCH RESEND v4 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.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
v4: collect tags
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 39385deafc68..a8343df2d424 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -310,6 +310,7 @@ 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 e43248e515b3..72c6aeed6e12 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);
 }
 

-- 
2.54.0

Re: [PATCH RESEND v4 0/3] drm/bridge: sii9234: use extcon to detect cable attachment

[Henrik Grimler]

Hello,

Friendly ping! This series has been reviewed/tested and still applies
cleanly on drm-misc-next, could it be merged?

Best regards,
Henrik Grimler

On Tue, Jun 02, 2026 at 08:36:47PM +0200, Henrik Grimler wrote:
> 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 v4:
> - Collect tags
> - Link to v3: https://lore.kernel.org/r/20250824-exynos4-sii9234-driver-v3-0-80849e716a37@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: a87fef0880c4f52769b5a3c2fc1b2d73aaa04eb3
> change-id: 20231218-exynos4-sii9234-driver-d817d4b511d5
> 
> Best regards,
> -- 
> Henrik Grimler <henrik@grimler.se>
>