linux-kernel - Re: [PATCH v5 2/3] i2c: imx: Check for I2SR

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Message-ID: <20201009075335.GC817@pengutronix.de>
Date:   Fri, 9 Oct 2020 09:53:35 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Christian Eggers <ceggers@...i.de>
Cc:     Oleksij Rempel <linux@...pel-privat.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        David Laight <David.Laight@...LAB.COM>,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        stable@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH v5 2/3] i2c: imx: Check for I2SR_IAL after every byte

On Wed, Oct 07, 2020 at 10:45:23AM +0200, Christian Eggers wrote:
> Arbitration Lost (IAL) can happen after every single byte transfer. If
> arbitration is lost, the I2C hardware will autonomously switch from
> master mode to slave. If a transfer is not aborted in this state,
> consecutive transfers will not be executed by the hardware and will
> timeout.
> 
> Signed-off-by: Christian Eggers <ceggers@...i.de>
> Tested (not extensively) on Vybrid VF500 (Toradex VF50):
> Tested-by: Krzysztof Kozlowski <krzk@...nel.org>
> Cc: stable@...r.kernel.org

Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>

Thank you!

> ---
>  drivers/i2c/busses/i2c-imx.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index cbdcab73a055..63575af41c09 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -490,6 +490,16 @@ static int i2c_imx_trx_complete(struct imx_i2c_struct *i2c_imx, bool atomic)
>  		dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
>  		return -ETIMEDOUT;
>  	}
> +
> +	/* check for arbitration lost */
> +	if (i2c_imx->i2csr & I2SR_IAL) {
> +		dev_dbg(&i2c_imx->adapter.dev, "<%s> Arbitration lost\n", __func__);
> +		i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
> +
> +		i2c_imx->i2csr = 0;
> +		return -EAGAIN;
> +	}
> +
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__);
>  	i2c_imx->i2csr = 0;
>  	return 0;
> -- 
> Christian Eggers
> Embedded software developer
> 
> Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
> Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRA 57918
> Persoenlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH
> Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRB 54477
> Geschaeftsfuehrer: Dr. Michael Neuhaeuser; Stephan Schenk; Walter Trauninger; Markus Zeiler
> 
> 
> 

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