linux-kernel - Re: [PATCH 2/4] i2c: core: add generic I2C GPIO recovery

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Message-ID: <20200805083629.GB1229@kunai>
Date:   Wed, 5 Aug 2020 10:36:29 +0200
From:   <wsa@...nel.org>
To:     Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Cc:     <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <robh+dt@...nel.org>,
        <ludovic.desroches@...rochip.com>, <nicolas.ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <linux@...linux.org.uk>,
        <kamel.bouhara@...tlin.com>
Subject: Re: [PATCH 2/4] i2c: core: add generic I2C GPIO recovery

On Tue, Aug 04, 2020 at 12:59:24PM +0300, Codrin Ciubotariu wrote:
> Multiple I2C bus drivers use similar bindings to obtain information needed
> for I2C recovery. For example, for platforms using device-tree, the
> properties look something like this:
> 
> &i2c {
> 	...
> 	pinctrl-names = "default", "gpio";
> 	pinctrl-0 = <&pinctrl_i2c_default>;
> 	pinctrl-1 = <&pinctrl_i2c_gpio>;
> 	sda-gpios = <&pio 0 GPIO_ACTIVE_HIGH>;
> 	scl-gpios = <&pio 1 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
> 	...
> }
> 
> For this reason, we can add this common initialization in the core. This
> way, other I2C bus drivers will be able to support GPIO recovery just by
> providing a pointer to platform's pinctrl and calling i2c_recover_bus()
> when SDA is stuck low.
> 
> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
> ---
Applied to for-next, thanks! Two minor change:

> +	/* for pinctrl state changes, we need all the information */
> +	if (!bri->pins_default || !bri->pins_gpio) {
> +		bri->pinctrl = NULL;
> +		bri->pins_default = NULL;
> +		bri->pins_gpio = NULL;
> +	} else {
> +		dev_info(dev, "using pinctrl states for GPIO recovery");
> +	}

I inverted the logic here:

 294         /* for pinctrl state changes, we need all the information */
 295         if (bri->pins_default && bri->pins_gpio) {
 296                 dev_info(dev, "using pinctrl states for GPIO recovery");
 297         } else {
 298                 bri->pinctrl = NULL;
 299                 bri->pins_default = NULL;
 300                 bri->pins_gpio = NULL;
 301         }

I think it is a bit easier to read if the desired path is not in the
else case.


> + * @pins_default: default state of SCL/SDA lines, when they are assigned to the
> + *      I2C bus. Optional. Populated internally for GPIO recovery, if a state with
> + *      the name PINCTRL_STATE_DEFAULT is found and pinctrl is valid.
> + * @pins_gpio: recovery state of SCL/SDA lines, when they are used as GPIOs.
> + *      Optional. Populated internally for GPIO recovery, if this state is called
> + *      "gpio" or "recovery" and pinctrl is valid.

Added "pinctrl" to "state of SCL/SDA" to make it clear.


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