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From:   Christian Eggers <ceggers@arri.de>
To:     Uwe =?ISO-8859-1?Q?Kleine=2DK=F6nig?= 
        <u.kleine-koenig@pengutronix.de>
CC:     Oleksij Rempel <linux@rempel-privat.de>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        <linux-kernel@vger.kernel.org>, <stable@vger.kernel.org>,
        NXP Linux Team <linux-imx@nxp.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        <linux-arm-kernel@lists.infradead.org>, <linux-i2c@vger.kernel.org>
Subject: Re: [PATCH 1/3] i2c: imx: Fix reset of I2SR_IAL flag
Date:   Thu, 17 Sep 2020 16:13:50 +0200
Message-ID: <16013235.tl8pWZfNaG@n95hx1g2>
Organization: Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
In-Reply-To: <20200917140235.igfq2hq63f4qqhrr@pengutronix.de>
References: <20200917122029.11121-1-ceggers@arri.de> <20200917122029.11121-2-ceggers@arri.de> <20200917140235.igfq2hq63f4qqhrr@pengutronix.de>
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Hello Uwe,

On Thursday, 17 September 2020, 16:02:35 CEST, Uwe Kleine-K?nig wrote:
> Hello,
> 
> On Thu, Sep 17, 2020 at 02:20:27PM +0200, Christian Eggers wrote:
> ...
> >  		/* check for arbitration lost */
> >  		if (temp & I2SR_IAL) {
> >  			temp &= ~I2SR_IAL;
> > +			temp |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IAL);
> >  			imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
> >  			return -EAGAIN;
> ...

> This looks strange. First the flag is cleared and then it is (in some
> cases) set again.
i.MX controllers require writing a 0 to clear these bits. Vybrid controllers
need writing a 1 for the same.

> If I2SR_IIF is set in temp you ack this irq without handling it. (Which
> might happen if atomic is set and irqs are off?!)
This patch is only about using the correct processor specific value for 
acknowledging an IRQ... But I think that returning EAGAIN (which aborts the
transfer) should be handling enough. At the next transfer, the controller will
be set back to master mode.

> I see this idiom is used in a few more places in the driver already, I
> didn't check but these might have the same problem maybe?

Best regards
Christian