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Message-ID: <20240601131053.GL491852@kernel.org>
Date: Sat, 1 Jun 2024 14:10:53 +0100
From: Simon Horman <horms@...nel.org>
To: Martin Hundebøll <martin@...nix.com>
Cc: Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
Marc Kleine-Budde <mkl@...gutronix.de>,
Vincent Mailhol <mailhol.vincent@...adoo.fr>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Markus Schneider-Pargmann <msp@...libre.com>,
linux-can@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] can: m_can: don't enable transceiver when probing
On Thu, May 30, 2024 at 12:57:58PM +0200, Martin Hundebøll wrote:
> The m_can driver sets and clears the CCCR.INIT bit during probe (both
> when testing the NON-ISO bit, and when configuring the chip). After
> clearing the CCCR.INIT bit, the transceiver enters normal mode, where it
> affects the CAN bus (i.e. it ACKs frames). This can cause troubles when
> the m_can node is only used for monitoring the bus, as one cannot setup
> listen-only mode before the device is probed.
>
> Rework the probe flow, so that the CCCR.INIT bit is only cleared when
> upping the device. First, the tcan4x5x driver is changed to stay in
> standby mode during/after probe. This in turn requires changes when
> setting bits in the CCCR register, as its CSR and CSA bits are always
> high in standby mode.
>
> Signed-off-by: Martin Hundebøll <martin@...nix.com>
> ---
> drivers/net/can/m_can/m_can.c | 169 ++++++++++++++++----------
> drivers/net/can/m_can/tcan4x5x-core.c | 13 +-
> 2 files changed, 116 insertions(+), 66 deletions(-)
>
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
...
> @@ -1694,21 +1732,26 @@ static int m_can_dev_setup(struct m_can_classdev *cdev)
> return -EINVAL;
> }
>
> - if (cdev->ops->init)
> - cdev->ops->init(cdev);
> -
> - return 0;
> + /* Forcing standby mode should be redunant, as the chip should be in
Hi Martin,
A minor nit from my side as it looks like there will be another revision
anyway.
redunant -> redundant
> + * 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);
> }
...
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