[PATCH v3 0/2] can: mcp251xfd: add XSTBYEN transceiver standby control

[PATCH v3 0/2] can: mcp251xfd: add XSTBYEN transceiver standby control

[Viken Dadhaniya]

The MCP251xFD provides a dedicated transceiver standby control function
via the INT0/GPIO0/XSTBY pin, controlled by the XSTBYEN bit in IOCON.
When enabled, the hardware automatically drives the pin low while the
controller is active and high when it enters Sleep mode, allowing
automatic standby control of an external CAN transceiver without
software intervention.

This series adds driver support for the XSTBYEN-based transceiver
standby control feature.

Tested on QCS6490 RB3 Gen2 with a PCAN-USB FD adapter: the transceiver is
active in normal mode, CAN communication works correctly, and the pin is
automatically managed across sleep and wake transitions.
---
v2 -> v3:

- Dropped device Tree change from this series.
- Configure xstbyen pin before bringing the controller into normal mode.
- Add a check in mcp251xfd_gpio_request() to ensure that GPIO0 cannot be
  used when xstbyen is enabled.

v2 Link: https://lore.kernel.org/all/20260316131950.859748-1-viken.dadhaniya@oss.qualcomm.com/

v1 -> v2:

- Drop the gpio-hog approach as suggested by Dmitry.
- Enable hardware‑managed transceiver standby control via the appropriate
  Device Tree property.

v1 Link: https://lore.kernel.org/all/20260108125200.2803112-1-viken.dadhaniya@oss.qualcomm.com/
---
Viken Dadhaniya (2):
  dt-bindings: can: mcp251xfd: add microchip,xstbyen property
  can: mcp251xfd: add support for XSTBYEN transceiver standby control

 .../bindings/net/can/microchip,mcp251xfd.yaml |  8 ++++
 .../net/can/spi/mcp251xfd/mcp251xfd-core.c    | 37 +++++++++++++++++++
 drivers/net/can/spi/mcp251xfd/mcp251xfd.h     |  1 +
 3 files changed, 46 insertions(+)

-- 
2.34.1

[PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Viken Dadhaniya]

Add the boolean property 'microchip,xstbyen' to enable the dedicated
transceiver standby control function on the INT0/GPIO0/XSTBY pin of
the MCP251xFD family.

Signed-off-by: Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>
---
v2 -> v3:

- No change.

v2 Link: https://lore.kernel.org/all/20260316131950.859748-2-viken.dadhaniya@oss.qualcomm.com/

v1 -> v2:

- Drop the gpio-hog approach as suggested by Dmitry.
- Add the microchip,xstbyen property to enable transceiver standby control.

v1 Link: https://lore.kernel.org/all/20260108125200.2803112-2-viken.dadhaniya@oss.qualcomm.com/
---
 .../devicetree/bindings/net/can/microchip,mcp251xfd.yaml  | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
index 2d13638ebc6a..28e494262cd9 100644
--- a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
+++ b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
@@ -44,6 +44,14 @@ properties:
       signals a pending RX interrupt.
     maxItems: 1
 
+  microchip,xstbyen:
+    type: boolean
+    description:
+      If present, configure the INT0/GPIO0/XSTBY pin as transceiver standby
+      control. The pin is driven low when the controller is active and high
+      when it enters Sleep mode, allowing automatic standby control of an
+      external CAN transceiver connected to this pin.
+
   spi-max-frequency:
     description:
       Must be half or less of "clocks" frequency.
-- 
2.34.1

[PATCH v3 2/2] can: mcp251xfd: add support for XSTBYEN transceiver standby control

[Viken Dadhaniya]

The MCP251xFD has a dedicated transceiver standby control function on
the INT0/GPIO0/XSTBY pin, controlled by the XSTBYEN bit in IOCON.
When enabled, the hardware automatically manages the transceiver
standby state: the pin is driven low when the controller is active
and high when it enters Sleep mode.

Enable this feature when the 'microchip,xstbyen' device tree property
is present.

Signed-off-by: Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>
---
v2 -> v3:

- Configure xstbyen pin before bringing the controller into normal mode.
- Add a check in mcp251xfd_gpio_request() to ensure that GPIO0 cannot be
  used when xstbyen is enabled.

v2 Link: https://lore.kernel.org/all/20260316131950.859748-3-viken.dadhaniya@oss.qualcomm.com/
---
 .../net/can/spi/mcp251xfd/mcp251xfd-core.c    | 37 +++++++++++++++++++
 drivers/net/can/spi/mcp251xfd/mcp251xfd.h     |  1 +
 2 files changed, 38 insertions(+)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index 9c86df08c2c5..92a86083c896 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -764,6 +764,31 @@ static void mcp251xfd_chip_stop(struct mcp251xfd_priv *priv,
 	mcp251xfd_chip_set_mode(priv, MCP251XFD_REG_CON_MODE_CONFIG);
 }
 
+static int mcp251xfd_chip_xstbyen_enable(const struct mcp251xfd_priv *priv)
+{
+	/* Configure the INT0/GPIO0/XSTBY pin as transceiver standby control:
+	 *
+	 * - XSTBYEN=1: route the pin to the transceiver standby function
+	 * - TRIS0=0:   set output direction; the reset default is 1 (input),
+	 *              which leaves the pin floating HIGH and keeps the
+	 *              transceiver in standby regardless of XSTBYEN
+	 * - LAT0=0:    drive pin LOW => transceiver active (not in standby)
+	 *
+	 * All three bits are included in the mask; only XSTBYEN is set in
+	 * val, so TRIS0 and LAT0 are cleared to 0 atomically.
+	 *
+	 * Pin behaviour by mode:
+	 * - Config mode: controlled by LAT0 (LAT0=0 => LOW => active)
+	 * - Normal mode: hardware drives pin LOW (active)
+	 * - Sleep mode:  hardware drives pin HIGH (standby)
+	 */
+	return regmap_update_bits(priv->map_reg, MCP251XFD_REG_IOCON,
+				  MCP251XFD_REG_IOCON_XSTBYEN |
+				  MCP251XFD_REG_IOCON_TRIS0 |
+				  MCP251XFD_REG_IOCON_LAT0,
+				  MCP251XFD_REG_IOCON_XSTBYEN);
+}
+
 static int mcp251xfd_chip_start(struct mcp251xfd_priv *priv)
 {
 	int err;
@@ -796,6 +821,12 @@ static int mcp251xfd_chip_start(struct mcp251xfd_priv *priv)
 
 	priv->can.state = CAN_STATE_ERROR_ACTIVE;
 
+	if (priv->xstbyen) {
+		err = mcp251xfd_chip_xstbyen_enable(priv);
+		if (err)
+			goto out_chip_stop;
+	}
+
 	err = mcp251xfd_chip_set_normal_mode(priv);
 	if (err)
 		goto out_chip_stop;
@@ -1805,6 +1836,11 @@ static int mcp251xfd_gpio_request(struct gpio_chip *chip, unsigned int offset)
 	u32 pin_mask = MCP251XFD_REG_IOCON_PM(offset);
 	int ret;
 
+	if (priv->xstbyen && offset == 0) {
+		netdev_err(priv->ndev, "Can't use GPIO 0 with XSTBYEN!\n");
+		return -EINVAL;
+	}
+
 	if (priv->rx_int && offset == 1) {
 		netdev_err(priv->ndev, "Can't use GPIO 1 with RX-INT!\n");
 		return -EINVAL;
@@ -2271,6 +2307,7 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	priv->pll_enable = pll_enable;
 	priv->reg_vdd = reg_vdd;
 	priv->reg_xceiver = reg_xceiver;
+	priv->xstbyen = device_property_present(&spi->dev, "microchip,xstbyen");
 	priv->devtype_data = *(struct mcp251xfd_devtype_data *)spi_get_device_match_data(spi);
 
 	/* Errata Reference:
diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
index 085d7101e595..d3f4704e2678 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h
@@ -672,6 +672,7 @@ struct mcp251xfd_priv {
 	struct gpio_desc *rx_int;
 	struct clk *clk;
 	bool pll_enable;
+	bool xstbyen;
 	struct regulator *reg_vdd;
 	struct regulator *reg_xceiver;
 
-- 
2.34.1

Re: [PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Marc Kleine-Budde]

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On 21.03.2026 19:20:30, Viken Dadhaniya wrote:
> Add the boolean property 'microchip,xstbyen' to enable the dedicated
> transceiver standby control function on the INT0/GPIO0/XSTBY pin of
> the MCP251xFD family.
>
> Signed-off-by: Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>

This series looks good to me, I think we need an Acked by the DT people.

regards,
Marc

> ---
> v2 -> v3:
>
> - No change.
>
> v2 Link: https://lore.kernel.org/all/20260316131950.859748-2-viken.dadhaniya@oss.qualcomm.com/
>
> v1 -> v2:
>
> - Drop the gpio-hog approach as suggested by Dmitry.
> - Add the microchip,xstbyen property to enable transceiver standby control.
>
> v1 Link: https://lore.kernel.org/all/20260108125200.2803112-2-viken.dadhaniya@oss.qualcomm.com/
> ---
>  .../devicetree/bindings/net/can/microchip,mcp251xfd.yaml  | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> index 2d13638ebc6a..28e494262cd9 100644
> --- a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> +++ b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> @@ -44,6 +44,14 @@ properties:
>        signals a pending RX interrupt.
>      maxItems: 1
>
> +  microchip,xstbyen:
> +    type: boolean
> +    description:
> +      If present, configure the INT0/GPIO0/XSTBY pin as transceiver standby
> +      control. The pin is driven low when the controller is active and high
> +      when it enters Sleep mode, allowing automatic standby control of an
> +      external CAN transceiver connected to this pin.
> +
>    spi-max-frequency:
>      description:
>        Must be half or less of "clocks" frequency.
> --
> 2.34.1
>
>
>

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
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Re: [PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Conor Dooley]

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On Sat, Mar 21, 2026 at 07:20:30PM +0530, Viken Dadhaniya wrote:
> Add the boolean property 'microchip,xstbyen' to enable the dedicated
> transceiver standby control function on the INT0/GPIO0/XSTBY pin of
> the MCP251xFD family.
> 
> Signed-off-by: Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>
> ---
> v2 -> v3:
> 
> - No change.
> 
> v2 Link: https://lore.kernel.org/all/20260316131950.859748-2-viken.dadhaniya@oss.qualcomm.com/
> 
> v1 -> v2:
> 
> - Drop the gpio-hog approach as suggested by Dmitry.
> - Add the microchip,xstbyen property to enable transceiver standby control.
> 
> v1 Link: https://lore.kernel.org/all/20260108125200.2803112-2-viken.dadhaniya@oss.qualcomm.com/
> ---
>  .../devicetree/bindings/net/can/microchip,mcp251xfd.yaml  | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> index 2d13638ebc6a..28e494262cd9 100644
> --- a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> +++ b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> @@ -44,6 +44,14 @@ properties:
>        signals a pending RX interrupt.
>      maxItems: 1
>  
> +  microchip,xstbyen:
> +    type: boolean
> +    description:
> +      If present, configure the INT0/GPIO0/XSTBY pin as transceiver standby
> +      control. The pin is driven low when the controller is active and high
> +      when it enters Sleep mode, allowing automatic standby control of an
> +      external CAN transceiver connected to this pin.

What I don't understand from this patch is why a property for this is
required.
Why can't this mode be implied from the lack of rx-int-gpios or
interrupts?

> +
>    spi-max-frequency:
>      description:
>        Must be half or less of "clocks" frequency.
> -- 
> 2.34.1
> 

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Re: [PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Marc Kleine-Budde]

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On 23.03.2026 19:30:00, Conor Dooley wrote:
> > diff --git a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> > index 2d13638ebc6a..28e494262cd9 100644
> > --- a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> > +++ b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> > @@ -44,6 +44,14 @@ properties:
> >        signals a pending RX interrupt.
> >      maxItems: 1
> >
> > +  microchip,xstbyen:
> > +    type: boolean
> > +    description:
> > +      If present, configure the INT0/GPIO0/XSTBY pin as transceiver standby
> > +      control. The pin is driven low when the controller is active and high
> > +      when it enters Sleep mode, allowing automatic standby control of an
> > +      external CAN transceiver connected to this pin.
>
> What I don't understand from this patch is why a property for this is
> required.
> Why can't this mode be implied from the lack of rx-int-gpios or
> interrupts?

The mcp251xfd has 2 GPIO pins. "rx-int-gpios" is for the other pin:
INT1/GPIO1. Also by default I don't want the controller to drive a pin
in a certain direction.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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Re: [PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Conor Dooley]

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On Mon, Mar 23, 2026 at 09:37:24PM +0100, Marc Kleine-Budde wrote:
> On 23.03.2026 19:30:00, Conor Dooley wrote:
> > > diff --git a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> > > index 2d13638ebc6a..28e494262cd9 100644
> > > --- a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> > > +++ b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
> > > @@ -44,6 +44,14 @@ properties:
> > >        signals a pending RX interrupt.
> > >      maxItems: 1
> > >
> > > +  microchip,xstbyen:
> > > +    type: boolean
> > > +    description:
> > > +      If present, configure the INT0/GPIO0/XSTBY pin as transceiver standby
> > > +      control. The pin is driven low when the controller is active and high
> > > +      when it enters Sleep mode, allowing automatic standby control of an
> > > +      external CAN transceiver connected to this pin.
> >
> > What I don't understand from this patch is why a property for this is
> > required.
> > Why can't this mode be implied from the lack of rx-int-gpios or
> > interrupts?
> 
> The mcp251xfd has 2 GPIO pins. "rx-int-gpios" is for the other pin:
> INT1/GPIO1. Also by default I don't want the controller to drive a pin
> in a certain direction.

Oke.
Acked-by: Conor Dooley <conor.dooley@microchip.com>

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Re: [PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Viken Dadhaniya]

Hi Marc,

Could you please let me know if the driver change looks acceptable to be merged?
Once merged, I will proceed with posting the device-tree change.

Thanks
Viken 

On 3/24/2026 3:00 AM, Conor Dooley wrote:
> On Mon, Mar 23, 2026 at 09:37:24PM +0100, Marc Kleine-Budde wrote:
>> On 23.03.2026 19:30:00, Conor Dooley wrote:
>>>> diff --git a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
>>>> index 2d13638ebc6a..28e494262cd9 100644
>>>> --- a/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
>>>> +++ b/Documentation/devicetree/bindings/net/can/microchip,mcp251xfd.yaml
>>>> @@ -44,6 +44,14 @@ properties:
>>>>        signals a pending RX interrupt.
>>>>      maxItems: 1
>>>>
>>>> +  microchip,xstbyen:
>>>> +    type: boolean
>>>> +    description:
>>>> +      If present, configure the INT0/GPIO0/XSTBY pin as transceiver standby
>>>> +      control. The pin is driven low when the controller is active and high
>>>> +      when it enters Sleep mode, allowing automatic standby control of an
>>>> +      external CAN transceiver connected to this pin.
>>>
>>> What I don't understand from this patch is why a property for this is
>>> required.
>>> Why can't this mode be implied from the lack of rx-int-gpios or
>>> interrupts?
>>
>> The mcp251xfd has 2 GPIO pins. "rx-int-gpios" is for the other pin:
>> INT1/GPIO1. Also by default I don't want the controller to drive a pin
>> in a certain direction.
> 
> Oke.
> Acked-by: Conor Dooley <conor.dooley@microchip.com>

Re: [PATCH v3 1/2] dt-bindings: can: mcp251xfd: add microchip,xstbyen property

[Marc Kleine-Budde]

[-- Attachment #1: Type: text/plain, Size: 551 bytes --]

On 31.03.2026 12:15:26, Viken Dadhaniya wrote:
> Could you please let me know if the driver change looks acceptable to be merged?
> Once merged, I will proceed with posting the device-tree change.

Applied to linux-can-next. It will be included in my next PR.

regards,
Marc

-- 
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