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

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Message-ID: <ac8c49fffac582176ba1899a85db84e0f5d5c7a6.1726669005.git.matthias.schiffer@ew.tq-group.com>
Date: Wed, 18 Sep 2024 16:21:53 +0200
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Martin Hundebøll <martin@...nix.com>,
	Markus Schneider-Pargmann <msp@...libre.com>,
	"Felipe Balbi (Intel)" <balbi@...nel.org>,
	Raymond Tan <raymond.tan@...el.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	linux-can@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux@...tq-group.com,
	Matthias Schiffer <matthias.schiffer@...tq-group.com>
Subject: [PATCH 1/2] can: m_can: set init flag earlier in probe

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>
---
 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 012c3d22b01dd..47481afb9add3 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1681,6 +1681,14 @@ 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.
+	 */
+	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);
 
@@ -1732,11 +1740,7 @@ 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)
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