linux-kernel - Re: [PATCH] i2c: rcar: ensure Gen3+ reset does not disturb local targets

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Message-ID: <ZpBL90Ko-B9oxCLK@shikoro>
Date: Thu, 11 Jul 2024 23:17:43 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: linux-renesas-soc@...r.kernel.org
Cc: Andi Shyti <andi.shyti@...nel.org>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: rcar: ensure Gen3+ reset does not disturb local
 targets

On Thu, Jul 11, 2024 at 10:30:44AM +0200, Wolfram Sang wrote:
> R-Car Gen3+ needs a reset before every controller transfer. That erases
> configuration of a potentially in parallel running local target
> instance. To avoid this disruption, avoid controller transfers if a
> local target is running. Also, disable SMBusHostNotify because it
> requires being a controller and local target at the same time.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>

Fixes: 3b770017b03a ("i2c: rcar: handle RXDMA HW behaviour on Gen3")

> ---
>  drivers/i2c/busses/i2c-rcar.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
> index 8f2ede534f30..29cbeda59f3e 100644
> --- a/drivers/i2c/busses/i2c-rcar.c
> +++ b/drivers/i2c/busses/i2c-rcar.c
> @@ -884,6 +884,10 @@ static int rcar_i2c_do_reset(struct rcar_i2c_priv *priv)
>  {
>  	int ret;
>  
> +	/* Don't reset if a slave instance is currently running */
> +	if (priv->slave)
> +		return -EISCONN;
> +
>  	ret = reset_control_reset(priv->rstc);
>  	if (ret)
>  		return ret;
> @@ -1176,6 +1180,7 @@ static int rcar_i2c_probe(struct platform_device *pdev)
>  	if (of_property_read_bool(dev->of_node, "smbus"))
>  		priv->flags |= ID_P_HOST_NOTIFY;
>  
> +	/* R-Car Gen3+ needs a reset before every transfer */
>  	if (priv->devtype >= I2C_RCAR_GEN3) {
>  		priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
>  		if (IS_ERR(priv->rstc)) {
> @@ -1186,6 +1191,9 @@ static int rcar_i2c_probe(struct platform_device *pdev)
>  		ret = reset_control_status(priv->rstc);
>  		if (ret < 0)
>  			goto out_pm_put;
> +
> +		/* hard reset disturbs HostNotify local target, so disable it */
> +		priv->flags &= ~ID_P_HOST_NOTIFY;
>  	}
>  
>  	ret = platform_get_irq(pdev, 0);
> -- 
> 2.43.0
> 

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