linux-kernel - Re: [PATCH v4 1/2] can: m_can: set init flag earlier in probe

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Message-ID: <b84140959d80439346df949f67882a9136c6977d.camel@ew.tq-group.com>
Date: Mon, 09 Dec 2024 11:05:24 +0100
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
Subject: Re: [PATCH v4 1/2] can: m_can: set init flag earlier in probe

On Mon, 2024-10-07 at 10:23 +0200, 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@...tq-group.com>
> Reviewed-by: Markus Schneider-Pargmann <msp@...libre.com>
> ---

Hi,

what's the status of these patches, are there remaining issues/comments? They
still apply cleanly to linux-next.

Best regards,
Matthias


> 
> v2: no changes
> v3: updated comment to mention Elkhart Lake
> v4: added Reviewed-by
> 
>  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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