linux-kernel - Re: [PATCH v2 8/9] i2c: riic: Add `riic_bus

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Message-ID: <Z2XhI4L9nzUqa22Z@ninjato>
Date: Fri, 20 Dec 2024 22:26:59 +0100
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Chris Brandt <chris.brandt@...esas.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Wolfram Sang <wsa@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	linux-renesas-soc@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2 8/9] i2c: riic: Add `riic_bus_barrier()` to check bus
 availability

On Wed, Dec 18, 2024 at 12:16:17AM +0000, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Introduce a new `riic_bus_barrier()` function to verify bus availability
> before initiating an I2C transfer. This function enhances the bus
> arbitration check by ensuring that the SDA and SCL lines are not held low,
> in addition to checking the BBSY flag using `readb_poll_timeout()`.
> 
> Previously, only the BBSY flag was checked to determine bus availability.
> However, it is possible for the SDA line to remain low even when BBSY = 0.
> This new implementation performs an additional check on the SDA and SCL
> lines to avoid potential bus contention issues.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

...

> -	if (riic_readb(riic, RIIC_ICCR2) & ICCR2_BBSY) {
> -		riic->err = -EBUSY;
> +	riic->err = riic_bus_barrier(riic);
> +	if (riic->err)
>  		goto out;
> -	}
>  
>  	reinit_completion(&riic->msg_done);
>  	riic->err = 0;

This initialization can go now. err is 0 already.

With that fixed:

Reviewed-by: Wolfram Sang <wsa+renesas@...g-engineering.com>


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