On Mon, Sep 23, 2024 at 05:32:15PM GMT, Matthias Schiffer wrote:
> 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@xxxxxxxxxxxxxxx>
Reviewed-by: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
Best
Markus
> ---
>
> v2: no changes
> v3: updated comment to mention Elkhart Lake
>
> 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..c85ac1b15f723 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;
> }
>
> + /* 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);
>
> @@ -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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