[PATCH v2 0/2] usb: gpio-sbu-mux: add FUSB340 and enable option for orientation

[PATCH v2 0/2] usb: gpio-sbu-mux: add FUSB340 and enable option for orientation

[Fabrice Gasnier]

Add a new compatible for FUSB340. Also mange the enable GPIO, when used as
orientation-switch only.
It is used on STM32MP25 DK boards, as orientation-switch only for
USB SuperSpeed lines on the Type-C connector, the enable GPIO being
connected to the SoC.

- - - - SoC - - - - - - - - - - board - - - - -
                        |                 USB-C
+------+  +----------+  |                   +-+
|      |--|  USB2PHY |<-----------------HS->|*|
|      |--|    HS    |<-----------------HS->|*|
|      |  +----------+  |                   | |
|      |                |    ________       | |
+ dwc3 |  +----------+  |   /        |<-SS->|*|
|      |  |          |<--->/         |<-SS->|*|
|      |--| ComboPHY |<--->  FUSB340 |      | |
|      |  |    SS    |  |  \  __     |<-SS->|*|
+------+  +----------+  |   \_en__sw_|<-SS->|*|
                        |     ^   ^         | |
          +----------+  |     |   |         ...
          [   GPIO   ]--------+   |
          [   GPIO   ]------------+
          +----------+  |
- - - - - - - - - - - - - - - - - - - - - - --

This is a subset of STM32MP25 Type-C support [1].

[1] https://lore.kernel.org/all/20260821-ucpd-host-fusb340-v7-2-rfc-v1-0-c5e27cbc0795@foss.st.com/

---
Changes in v2:
- Added Conor's Acked-by
- Fix new driver issues introduced in v1 as reported by Sashiko, on
  a possible race during probe and a possible glitch upon enable.
- Link to v1: https://patch.msgid.link/20260825-usb-fusb340-v1-v1-0-2191179b0661@foss.st.com

To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: Bjorn Andersson <andersson@kernel.org>
To: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: linux-usb@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

---
Fabrice Gasnier (2):
      dt-bindings: usb: gpio-sbu-mux: Add compatible for FUSB340
      usb: typec: mux: gpio-sbu: enable when only used for orientation

 Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml |  1 +
 drivers/usb/typec/mux/gpio-sbu-mux.c                    | 14 +++++++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)
---
base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
change-id: 20260825-usb-fusb340-v1-f060a5f84d3c

Best regards,
--  
Fabrice Gasnier <fabrice.gasnier@foss.st.com>

[PATCH v2 1/2] dt-bindings: usb: gpio-sbu-mux: Add compatible for FUSB340

[Fabrice Gasnier]

Add a compatible for the FUSB340 GPIO-based 2:1 SuperSpeed switch
with enable-gpios and select-gpios controls. The switch can be used
in Type-C applications where a reversible cable requires a switch.

Suggested-by: Marek Vasut <marex@nabladev.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
---
 Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml b/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml
index 793662f6f3bf..c0e60848d8ab 100644
--- a/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml
+++ b/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml
@@ -22,6 +22,7 @@ properties:
           - nxp,cbdtu02043
           - onnn,fsusb42
           - onnn,fsusb43l10x
+          - onnn,fusb340
           - pericom,pi3usb102
           - ti,tmuxhs4212
       - const: gpio-sbu-mux

-- 
2.43.0

[PATCH v2 2/2] usb: typec: mux: gpio-sbu: enable when only used for orientation

[Fabrice Gasnier]

When used as orientation-switch only (no mode-switch, e.g. no altmode),
the optional enable gpio remains disabled.
Enable it from the switch_set() routine, in this case, when the
orientation is set and the enable-gpios property has been provided.
Move enable GPIO configuration after the swapped configuration has
been done, to avoid possible glitches in case both signals are changed.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
---
Changes in v2
- fix issues reported by Sashiko: probe mode-switch property before
  registering Type-C switch, to avoid possible race. Configure enable
  GPIO after swapp GPIO has been configured, in case both transition.
---
 drivers/usb/typec/mux/gpio-sbu-mux.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/typec/mux/gpio-sbu-mux.c b/drivers/usb/typec/mux/gpio-sbu-mux.c
index 1834f1a2dd9d..120f1ab5dbcb 100644
--- a/drivers/usb/typec/mux/gpio-sbu-mux.c
+++ b/drivers/usb/typec/mux/gpio-sbu-mux.c
@@ -17,6 +17,7 @@ struct gpio_sbu_mux {
 
 	struct typec_switch_dev *sw;
 	struct typec_mux_dev *mux;
+	bool mode_switch;
 
 	struct mutex lock; /* protect enabled and swapped */
 	bool enabled;
@@ -40,19 +41,24 @@ static int gpio_sbu_switch_set(struct typec_switch_dev *sw,
 		enabled = false;
 		break;
 	case TYPEC_ORIENTATION_NORMAL:
+		if (!sbu_mux->mode_switch)
+			enabled = true;
 		swapped = false;
 		break;
 	case TYPEC_ORIENTATION_REVERSE:
+		if (!sbu_mux->mode_switch)
+			enabled = true;
 		swapped = true;
 		break;
 	}
 
-	if (enabled != sbu_mux->enabled)
-		gpiod_set_value_cansleep(sbu_mux->enable_gpio, enabled);
-
 	if (swapped != sbu_mux->swapped)
 		gpiod_set_value_cansleep(sbu_mux->select_gpio, swapped);
 
+	/* If both enabled and swapped transition, set enable GPIO after to avoid glitches */
+	if (enabled != sbu_mux->enabled)
+		gpiod_set_value_cansleep(sbu_mux->enable_gpio, enabled);
+
 	sbu_mux->enabled = enabled;
 	sbu_mux->swapped = swapped;
 
@@ -125,6 +131,8 @@ static int gpio_sbu_mux_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(sbu_mux->sw),
 				     "failed to register typec switch\n");
 
+	sbu_mux->mode_switch = device_property_read_bool(dev, "mode-switch");
+
 	mux_desc.drvdata = sbu_mux;
 	mux_desc.fwnode = dev_fwnode(dev);
 	mux_desc.set = gpio_sbu_mux_set;

-- 
2.43.0

Re: [PATCH v2 2/2] usb: typec: mux: gpio-sbu: enable when only used for orientation

[Fabrice Gasnier]

On 8/26/26 11:53, Fabrice Gasnier wrote:
> When used as orientation-switch only (no mode-switch, e.g. no altmode),
> the optional enable gpio remains disabled.
> Enable it from the switch_set() routine, in this case, when the
> orientation is set and the enable-gpios property has been provided.
> Move enable GPIO configuration after the swapped configuration has
> been done, to avoid possible glitches in case both signals are changed.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
> ---
> Changes in v2
> - fix issues reported by Sashiko: probe mode-switch property before
>   registering Type-C switch, to avoid possible race. Configure enable
>   GPIO after swapp GPIO has been configured, in case both transition.
> ---
>  drivers/usb/typec/mux/gpio-sbu-mux.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/mux/gpio-sbu-mux.c b/drivers/usb/typec/mux/gpio-sbu-mux.c

[...]

>  
> @@ -125,6 +131,8 @@ static int gpio_sbu_mux_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, PTR_ERR(sbu_mux->sw),
>  				     "failed to register typec switch\n");
>  
> +	sbu_mux->mode_switch = device_property_read_bool(dev, "mode-switch");
> +

I've missed to update that, I'll send a V3.
Sorry for the noise,
BR,
Fabrice

>  	mux_desc.drvdata = sbu_mux;
>  	mux_desc.fwnode = dev_fwnode(dev);
>  	mux_desc.set = gpio_sbu_mux_set;
> 

Re: [PATCH v2 2/2] usb: typec: mux: gpio-sbu: enable when only used for orientation

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The `mode-switch` property is probed after registering the Type-C switch, contradicting the v2 commit message and introducing a race condition where incoming callbacks might use uninitialized state.
--

commit c810037786c450b0d450c67a1bf5b0c47390d167
Author: Fabrice Gasnier <fabrice.gasnier@foss.st.com>

usb: typec: mux: gpio-sbu: enable when only used for orientation

This commit modifies the GPIO SBU mux driver to enable the optional GPIO
when used purely as an orientation switch. It adds logic to check the
mode-switch property and adjust the GPIO state accordingly in the switch_set
callback.

> diff --git a/drivers/usb/typec/mux/gpio-sbu-mux.c b/drivers/usb/typec/mux/gpio-sbu-mux.c
> index 1834f1a2dd9dd..120f1ab5dbcb3 100644
> --- a/drivers/usb/typec/mux/gpio-sbu-mux.c
> +++ b/drivers/usb/typec/mux/gpio-sbu-mux.c
> @@ -40,19 +41,24 @@ static int gpio_sbu_switch_set(struct typec_switch_dev *sw,
>  		enabled = false;
>  		break;
>  	case TYPEC_ORIENTATION_NORMAL:
> +		if (!sbu_mux->mode_switch)
> +			enabled = true;
>  		swapped = false;
>  		break;

[ ... ]

> @@ -125,6 +131,8 @@ static int gpio_sbu_mux_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, PTR_ERR(sbu_mux->sw),
>  				     "failed to register typec switch\n");
>  
> +	sbu_mux->mode_switch = device_property_read_bool(dev, "mode-switch");
> +
>  	mux_desc.drvdata = sbu_mux;

[Severity: High]
Can this registration order introduce a regression where incoming callbacks
use uninitialized state?

If a Type-C switch event occurs immediately after typec_switch_register()
returns but before device_property_read_bool() executes, could the
gpio_sbu_switch_set() callback incorrectly evaluate sbu_mux->mode_switch as
false? The memory for sbu_mux is zeroed by devm_kzalloc, which might cause
the enable GPIO to be incorrectly asserted during this initialization window.

Additionally, the patch description mentions probing the mode-switch property
before registering the Type-C switch to avoid a race condition. Should this
property read be moved above the typec_switch_register() call to prevent
this issue?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260826-usb-fusb340-v1-v2-0-994a03c9ae45@foss.st.com?part=2