linux-kernel - [PATCH 7/7] can: m_can: add optional support for reset

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Message-Id: <20250812-m_can-fix-state-handling-v1-7-b739e06c0a3b@pengutronix.de>
Date: Tue, 12 Aug 2025 19:36:57 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Chandrasekar Ramakrishnan <rcsekar@...sung.com>, 
 Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
 Patrik Flykt <patrik.flykt@...ux.intel.com>, 
 Dong Aisheng <b29396@...escale.com>, Fengguang Wu <fengguang.wu@...el.com>, 
 Varka Bhadram <varkabhadram@...il.com>, Wu Bo <wubo.oduw@...il.com>, 
 Markus Schneider-Pargmann <msp@...libre.com>, 
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 7/7] can: m_can: add optional support for reset

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.

Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.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 c24ea0e5599f..0a6d4b523c33 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"
 
@@ -1833,6 +1834,7 @@ static int m_can_close(struct net_device *dev)
 
 	close_candev(dev);
 
+	reset_control_assert(cdev->rsts);
 	m_can_clk_stop(cdev);
 	phy_power_off(cdev->transceiver);
 
@@ -2075,11 +2077,15 @@ static int m_can_open(struct net_device *dev)
 	if (err)
 		goto out_phy_power_off;
 
+	err = reset_control_deassert(cdev->rsts);
+	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)
@@ -2135,6 +2141,8 @@ 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->rsts);
 exit_disable_clks:
 	m_can_clk_stop(cdev);
 out_phy_power_off:
@@ -2425,15 +2433,23 @@ int m_can_class_register(struct m_can_classdev *cdev)
 		}
 	}
 
+	cdev->rsts = devm_reset_control_get_optional_shared(cdev->dev, NULL);
+	if (IS_ERR(cdev->rsts))
+		return PTR_ERR(cdev->rsts);
+
 	ret = m_can_clk_start(cdev);
 	if (ret)
 		return ret;
 
+	ret = reset_control_deassert(cdev->rsts);
+	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) {
@@ -2462,8 +2478,10 @@ 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 rest and stop clocks.
+	 * They will be reactivated once the M_CAN device is opened
 	 */
+	reset_control_assert(cdev->rsts);
 	m_can_clk_stop(cdev);
 
 	return 0;
@@ -2471,6 +2489,8 @@ 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->rsts);
 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..5e901d5bf6ff 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 *rsts;
 
 	struct workqueue_struct *tx_wq;
 	struct phy *transceiver;

-- 
2.50.1