From: kbouhara <kamel.bouhara@bootlin•com>
To: Codrin Ciubotariu <codrin.ciubotariu@microchip•com>,
linux-i2c@vger•kernel.org, linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org
Cc: ludovic.desroches@microchip•com, alexandre.belloni@bootlin•com,
wsa@the-dreams•de
Subject: Re: [PATCH] i2c: at91: Send bus clear command if SCL or SDA is down
Date: Thu, 19 Sep 2019 17:06:18 +0200 [thread overview]
Message-ID: <1ed845e5-3835-f1aa-099a-b67c3bc16076@bootlin.com> (raw)
In-Reply-To: <20190911095854.5141-1-codrin.ciubotariu@microchip.com>
On 9/11/19 11:58 AM, Codrin Ciubotariu wrote:
> After a transfer timeout, some faulty I2C slave devices might hold down
> the SCL or the SDA pins. We can generate a bus clear command, hoping that
> the slave might release the pins.
>
> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip•com>
> ---
> drivers/i2c/busses/i2c-at91-master.c | 20 ++++++++++++++++++++
> drivers/i2c/busses/i2c-at91.h | 6 +++++-
> 2 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
> index a3fcc35ffd3b..5f544a16db96 100644
> --- a/drivers/i2c/busses/i2c-at91-master.c
> +++ b/drivers/i2c/busses/i2c-at91-master.c
> @@ -599,6 +599,26 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
> at91_twi_write(dev, AT91_TWI_CR,
> AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
> }
> +
> + /*
> + * After timeout, some faulty I2C slave devices might hold SCL/SDA down;
> + * we can send a bus clear command, hoping that the pins will be
> + * released
> + */
> + if (!(dev->transfer_status & AT91_TWI_SDA) ||
> + !(dev->transfer_status & AT91_TWI_SCL)) {
> + dev_dbg(dev->dev,
> + "SDA/SCL are down; sending bus clear command\n");
> + if (dev->use_alt_cmd) {
> + unsigned int acr;
> +
> + acr = at91_twi_read(dev, AT91_TWI_ACR);
> + acr &= ~AT91_TWI_ACR_DATAL_MASK;
> + at91_twi_write(dev, AT91_TWI_ACR, acr);
> + }
> + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);
This bit is not documented on SoCs before SAMA5D2/D4, this write
shouldn't be done unconditionally.
--
Kamel Bouhara, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
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linux-arm-kernel mailing list
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-09-19 15:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190911095854.5141-1-codrin.ciubotariu@microchip.com>
2019-09-14 19:05 ` [PATCH] i2c: at91: Send bus clear command if SCL or SDA is down Ludovic Desroches
2019-09-16 5:20 ` Claudiu.Beznea
2019-09-19 15:06 ` kbouhara [this message]
2019-09-19 16:25 ` Codrin.Ciubotariu
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