Re: [PATCH v2 7/7] can: m_can: add optional support for reset

["Markus Schneider-Pargmann" <msp@baylibre.com>]

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On Tue Sep 9, 2025 at 7:53 PM CEST, Marc Kleine-Budde wrote:
> In some SoCs (observed on the STM32MP15) the M_CAN IP core keeps the
> CAN state and CAN error counters over an internal reset cycle. The
> STM32MP15 SoC provides an external reset, which is shared between both
> M_CAN cores.
>
> Add support for an optional external reset. Take care of shared
> resets, de-assert reset during the probe phase in
> m_can_class_register() and while the interface is up, assert the reset
> otherwise.
>
> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
>  drivers/net/can/m_can/m_can.c | 26 +++++++++++++++++++++++---
>  drivers/net/can/m_can/m_can.h |  1 +
>  2 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index 9528af8500af..93085bf1c267 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -23,6 +23,7 @@
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/reset.h>
>  
>  #include "m_can.h"
>  
> @@ -1834,6 +1835,7 @@ static int m_can_close(struct net_device *dev)
>  
>  	close_candev(dev);
>  
> +	reset_control_assert(cdev->rst);
>  	m_can_clk_stop(cdev);
>  	phy_power_off(cdev->transceiver);
>  
> @@ -2076,11 +2078,15 @@ static int m_can_open(struct net_device *dev)
>  	if (err)
>  		goto out_phy_power_off;
>  
> +	err = reset_control_deassert(cdev->rst);
> +	if (err)
> +		goto exit_disable_clks;
> +
>  	/* open the can device */
>  	err = open_candev(dev);
>  	if (err) {
>  		netdev_err(dev, "failed to open can device\n");
> -		goto exit_disable_clks;
> +		goto out_reset_control_assert;
>  	}
>  
>  	if (cdev->is_peripheral)
> @@ -2136,6 +2142,8 @@ static int m_can_open(struct net_device *dev)
>  	else
>  		napi_disable(&cdev->napi);
>  	close_candev(dev);
> +out_reset_control_assert:
> +	reset_control_assert(cdev->rst);
>  exit_disable_clks:
>  	m_can_clk_stop(cdev);
>  out_phy_power_off:
> @@ -2426,15 +2434,23 @@ int m_can_class_register(struct m_can_classdev *cdev)
>  		}
>  	}
>  
> +	cdev->rst = devm_reset_control_get_optional_shared(cdev->dev, NULL);
> +	if (IS_ERR(cdev->rst))
> +		return PTR_ERR(cdev->rst);

Should this print an error message here?

Best
Markus

> +
>  	ret = m_can_clk_start(cdev);
>  	if (ret)
>  		return ret;
>  
> +	ret = reset_control_deassert(cdev->rst);
> +	if (ret)
> +		goto clk_disable;
> +
>  	if (cdev->is_peripheral) {
>  		ret = can_rx_offload_add_manual(cdev->net, &cdev->offload,
>  						NAPI_POLL_WEIGHT);
>  		if (ret)
> -			goto clk_disable;
> +			goto out_reset_control_assert;
>  	}
>  
>  	if (!cdev->net->irq) {
> @@ -2463,8 +2479,10 @@ int m_can_class_register(struct m_can_classdev *cdev)
>  		 KBUILD_MODNAME, cdev->net->irq, cdev->version);
>  
>  	/* Probe finished
> -	 * Stop clocks. They will be reactivated once the M_CAN device is opened
> +	 * Assert reset and stop clocks.
> +	 * They will be reactivated once the M_CAN device is opened
>  	 */
> +	reset_control_assert(cdev->rst);
>  	m_can_clk_stop(cdev);
>  
>  	return 0;
> @@ -2472,6 +2490,8 @@ int m_can_class_register(struct m_can_classdev *cdev)
>  rx_offload_del:
>  	if (cdev->is_peripheral)
>  		can_rx_offload_del(&cdev->offload);
> +out_reset_control_assert:
> +	reset_control_assert(cdev->rst);
>  clk_disable:
>  	m_can_clk_stop(cdev);
>  
> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
> index bd4746c63af3..7b7600697c6b 100644
> --- a/drivers/net/can/m_can/m_can.h
> +++ b/drivers/net/can/m_can/m_can.h
> @@ -86,6 +86,7 @@ struct m_can_classdev {
>  	struct device *dev;
>  	struct clk *hclk;
>  	struct clk *cclk;
> +	struct reset_control *rst;
>  
>  	struct workqueue_struct *tx_wq;
>  	struct phy *transceiver;


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