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From:   gregkh@linuxfoundation.org
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Marc Kleine-Budde <mkl@pengutronix.de>,
        Torin Cooper-Bennun <torin@maxiluxsystems.com>
Subject: [PATCH 5.4 013/168] can: tcan4x5x: tcan4x5x_init(): fix initialization - clear MRAM before entering Normal Mode
Date:   Mon, 15 Mar 2021 14:54:05 +0100
Message-Id: <20210315135550.775526741@linuxfoundation.org>
In-Reply-To: <20210315135550.333963635@linuxfoundation.org>
References: <20210315135550.333963635@linuxfoundation.org>
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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

From: Torin Cooper-Bennun <torin@maxiluxsystems.com>

commit 2712625200ed69c642b9abc3a403830c4643364c upstream.

This patch prevents a potentially destructive race condition. The
device is fully operational on the bus after entering Normal Mode, so
zeroing the MRAM after entering this mode may lead to loss of
information, e.g. new received messages.

This patch fixes the problem by first initializing the MRAM, then
bringing the device into Normale Mode.

Fixes: 5443c226ba91 ("can: tcan4x5x: Add tcan4x5x driver to the kernel")
Link: https://lore.kernel.org/r/20210226163440.313628-1-torin@maxiluxsystems.com
Suggested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Torin Cooper-Bennun <torin@maxiluxsystems.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/can/m_can/tcan4x5x.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/net/can/m_can/tcan4x5x.c
+++ b/drivers/net/can/m_can/tcan4x5x.c
@@ -325,14 +325,14 @@ static int tcan4x5x_init(struct m_can_cl
 	if (ret)
 		return ret;
 
+	/* Zero out the MCAN buffers */
+	m_can_init_ram(cdev);
+
 	ret = regmap_update_bits(tcan4x5x->regmap, TCAN4X5X_CONFIG,
 				 TCAN4X5X_MODE_SEL_MASK, TCAN4X5X_MODE_NORMAL);
 	if (ret)
 		return ret;
 
-	/* Zero out the MCAN buffers */
-	m_can_init_ram(cdev);
-
 	return ret;
 }