linux-kernel - Re: [PATCH v2 1/3] i2c: imx: Fix reset of I2SR

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Date:   Tue, 6 Oct 2020 08:05:28 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...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>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v2 1/3] i2c: imx: Fix reset of I2SR_IAL flag

On Fri, Oct 02, 2020 at 05:23:03PM +0200, Christian Eggers wrote:
> According to the "VFxxx Controller Reference Manual" (and the comment
> block starting at line 97), Vybrid requires writing a one for clearing
> an interrupt flag. Syncing the method for clearing I2SR_IIF in
> i2c_imx_isr().
> 
> Signed-off-by: Christian Eggers <ceggers@...i.de>
> Cc: stable@...r.kernel.org
> ---
>  drivers/i2c/busses/i2c-imx.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 0ab5381aa012..34648df7f1a6 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -424,7 +424,12 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool a
>  
>  		/* check for arbitration lost */
>  		if (temp & I2SR_IAL) {
> -			temp &= ~I2SR_IAL;
> +			/*
> +			 * i2sr_clr_opcode is the value to clear all interrupts.
> +			 * Here we want to clear only I2SR_IAL, so we write
> +			 * ~i2sr_clr_opcode with just the I2SR_IAL bit toggled.
> +			 */
> +			temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ I2SR_IAL;
>  			imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
>  			return -EAGAIN;

Could we please move clearing an irq to a dedicated function? Such that
it looks like:

	/* check for arbitration lost */
	if (temp & I2SR_IAL) {
		i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
		return -EAGAIN;
	}

Then you also don't need to duplicate the describing comment but just
add it to the implementation of i2c_imx_clear_irq().

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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