Re: [PATCH 4/6] i2c: spacemit: check SDA instead of SCL after bus reset

From: Aurelien Jarno <aurelien@aurel32.net>
To: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Cc: Andi Shyti <andi.shyti@kernel.org>, Yixun Lan <dlan@gentoo.org>,
	Alex Elder <elder@riscstar.com>,
	Troy Mitchell <troymitchell988@gmail.com>,
	linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, spacemit@lists.linux.dev
Subject: Re: [PATCH 4/6] i2c: spacemit: check SDA instead of SCL after bus reset
Date: Mon, 22 Sep 2025 22:56:04 +0200	[thread overview]
Message-ID: <aNG35Dwg7wWivSHJ@aurel32.net> (raw)
In-Reply-To: <20250827-k1-i2c-atomic-v1-4-e59bea02d680@linux.spacemit.com>

On 2025-08-27 15:39, Troy Mitchell wrote:
> After calling spacemit_i2c_conditionally_reset_bus(),
> the controller should ensure that the SDA line is release
> before proceeding.
> 
> Previously, the driver checked the SCL line instead,
> which does not guarantee that the bus is truly idle.
> 
> This patch changes the check to verify SDA. This ensures
> proper bus recovery and avoids potential communication errors
> after a conditional reset.
> 
> Fixes: 5ea558473fa31 ("i2c: spacemit: add support for SpacemiT K1 SoC")
> Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
> ---
>  drivers/i2c/busses/i2c-k1.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
> index c1656b78f1681729ccc2ebca6e290259d14889d9..4d78ee7b6929ee43771e500d4f85d9e55e68b221 100644
> --- a/drivers/i2c/busses/i2c-k1.c
> +++ b/drivers/i2c/busses/i2c-k1.c
> @@ -172,9 +172,9 @@ static void spacemit_i2c_conditionally_reset_bus(struct spacemit_i2c_dev *i2c)
>  	spacemit_i2c_reset(i2c);
>  	usleep_range(10, 20);
>  
> -	/* check scl status again */
> +	/* check sda again here */
>  	status = readl(i2c->base + SPACEMIT_IBMR);
> -	if (!(status & SPACEMIT_BMR_SCL))
> +	if (!(status & SPACEMIT_BMR_SDA))
>  		dev_warn_ratelimited(i2c->dev, "unit reset failed\n");
>  }

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                     http://aurel32.net