netdev - [PATCH net 1/2] can: m_can: set init flag earlier in probe

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Message-ID: <20241218121722.2311963-2-mkl@pengutronix.de>
Date: Wed, 18 Dec 2024 13:10:27 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	linux-can@...r.kernel.org,
	kernel@...gutronix.de,
	Matthias Schiffer <matthias.schiffer@...tq-group.com>,
	Markus Schneider-Pargmann <msp@...libre.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net 1/2] can: m_can: set init flag earlier in probe

From: Matthias Schiffer <matthias.schiffer@...tq-group.com>

While an m_can controller usually already has the init flag from a
hardware reset, no such reset happens on the integrated m_can_pci of the
Intel Elkhart Lake. If the CAN controller is found in an active state,
m_can_dev_setup() would fail because m_can_niso_supported() calls
m_can_cccr_update_bits(), which refuses to modify any other configuration
bits when CCCR_INIT is not set.

To avoid this issue, set CCCR_INIT before attempting to modify any other
configuration flags.

Fixes: cd5a46ce6fa6 ("can: m_can: don't enable transceiver when probing")
Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
Reviewed-by: Markus Schneider-Pargmann <msp@...libre.com>
Link: https://patch.msgid.link/e247f331cb72829fcbdfda74f31a59cbad1a6006.1728288535.git.matthias.schiffer@ew.tq-group.com
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/m_can/m_can.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 533bcb77c9f9..67c404fbe166 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1695,6 +1695,14 @@ static int m_can_dev_setup(struct m_can_classdev *cdev)
 		return -EINVAL;
 	}
 
+	/* Write the INIT bit, in case no hardware reset has happened before
+	 * the probe (for example, it was observed that the Intel Elkhart Lake
+	 * SoCs do not properly reset the CAN controllers on reboot)
+	 */
+	err = m_can_cccr_update_bits(cdev, CCCR_INIT, CCCR_INIT);
+	if (err)
+		return err;
+
 	if (!cdev->is_peripheral)
 		netif_napi_add(dev, &cdev->napi, m_can_poll);
 
@@ -1746,11 +1754,7 @@ static int m_can_dev_setup(struct m_can_classdev *cdev)
 		return -EINVAL;
 	}
 
-	/* Forcing standby mode should be redundant, as the chip should be in
-	 * standby after a reset. Write the INIT bit anyways, should the chip
-	 * be configured by previous stage.
-	 */
-	return m_can_cccr_update_bits(cdev, CCCR_INIT, CCCR_INIT);
+	return 0;
 }
 
 static void m_can_stop(struct net_device *dev)

base-commit: 954a2b40719a21e763a1bba2f0da92347e058fce
-- 
2.45.2