can: m_can: add support for optional reset

This patch has been split from the original series [1].

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.

[1] https://lore.kernel.org/all/20250923-m_can-fix-state-handling-v3-0-06d8baccadbf@pengutronix.de

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://patch.msgid.link/20251008-m_can-add-reset-v1-1-49f0bbf820c4@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index ad4f577c1ef7898e193c43c0744cd04fe585d50a..48b7a67336b5e92964d9925687d8b584564bf872 100644 (file)
--- 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"
 
@@ -1827,6 +1828,7 @@ 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);
 
@@ -2069,11 +2071,15 @@ 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)
@@ -2129,6 +2135,8 @@ out_wq_fail:
        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:
@@ -2417,15 +2425,24 @@ 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 dev_err_probe(cdev->dev, PTR_ERR(cdev->rst),
+                                    "Failed to get reset line\n");
+
        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) {
@@ -2454,8 +2471,10 @@ 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;
@@ -2463,6 +2482,8 @@ 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 bd4746c63af3f0a032910644dfd48a9ebb3a6168..7b7600697c6bc52f821730d0a373adb713155831 100644 (file)
--- 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;