linux-kernel - Re: [PATCH v2 1/2] mfd: da9062: enable being a system-power-controller

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Message-ID: <Yqj2cHuhjRhSIbDt@google.com>
Date:   Tue, 14 Jun 2022 21:58:24 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Helmut Grohne <helmut.grohne@...enta.de>
Cc:     Support Opensource <support.opensource@...semi.com>,
        linux-kernel@...r.kernel.org,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Mark Brown <broonie@...nel.org>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [PATCH v2 1/2] mfd: da9062: enable being a
 system-power-controller

On Fri, 22 Apr 2022, Helmut Grohne wrote:

> The DA9062 can be the device used to power the CPU. In that case, it can
> be used to power off the system. In the CONTROL_A register, the M_*_EN
> bits must be zero for the corresponding *_EN bits to have an effect. We
> zero them all to turn off the system.
> 
> Signed-off-by: Helmut Grohne <helmut.grohne@...enta.de>
> ---
>  drivers/mfd/da9062-core.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> This series effectively is a rebased resend. The earlier posting was
> https://lore.kernel.org/all/20200107120559.GA700@laureti-dev/. At that time,
> Adam Thomson critisized the use of regmap and i2c inside a pm_power_off hook
> since irqs are disabled. He reached out to Lee Jones, who asked Mark Brown and
> Wolfram Sang, but never got any reply. I noted that a fair number of other
> drivers do use regmap and i2c despite this issue. In the mean time, more
> instances were added:
>  * drivers/mfd/acer-ec-a500.c uses i2c
>  * drivers/mfd/ntxec.c uses i2c
>  * drivers/mfd/rk808.c uses regmap and i2c
> Given that we proceeded with accepting the use of i2c and regmap inside
> pm_power_off hooks, I think we can proceed with this patch as well.
> 
> Helmut
> 
> diff --git a/drivers/mfd/da9062-core.c b/drivers/mfd/da9062-core.c
> index 2774b2cbaea6..e7af5b5f16e0 100644
> --- a/drivers/mfd/da9062-core.c
> +++ b/drivers/mfd/da9062-core.c
> @@ -620,6 +620,23 @@ static const struct of_device_id da9062_dt_ids[] = {
>  };
>  MODULE_DEVICE_TABLE(of, da9062_dt_ids);
>  
> +/* Hold client since pm_power_off is global. */

Please drop this comment.

> +static struct i2c_client *da9062_i2c_client;
> +
> +static void da9062_power_off(void)
> +{
> +	struct da9062 *chip = i2c_get_clientdata(da9062_i2c_client);
> +	const unsigned int mask = DA9062AA_SYSTEM_EN_MASK |
> +		DA9062AA_POWER_EN_MASK | DA9062AA_POWER1_EN_MASK |
> +		DA9062AA_M_SYSTEM_EN_MASK | DA9062AA_M_POWER_EN_MASK |
> +		DA9062AA_M_POWER1_EN_MASK;
> +	int ret = regmap_update_bits(chip->regmap, DA9062AA_CONTROL_A, mask, 0);

This is messy.  Please separate declarations and assignments here.

The top one is passable.

> +	if (ret < 0)
> +		dev_err(&da9062_i2c_client->dev,
> +			"DA9062AA_CONTROL_A update failed, %d\n", ret);

You're talking to the user here.

Please use language that is more user-friendly.

> +}
> +
>  static int da9062_i2c_probe(struct i2c_client *i2c,
>  	const struct i2c_device_id *id)
>  {
> @@ -720,6 +737,15 @@ static int da9062_i2c_probe(struct i2c_client *i2c,
>  		return ret;
>  	}
>  
> +	if (of_device_is_system_power_controller(i2c->dev.of_node)) {
> +		if (!pm_power_off) {
> +			da9062_i2c_client = i2c;
> +			pm_power_off = da9062_power_off;
> +		} else {
> +			dev_warn(&i2c->dev, "Poweroff callback already assigned\n");

Do we really mind/care?

Is there anything we can do about it?

Thus, do we really need to warn() about it?

> +		}
> +	}
> +
>  	return ret;
>  }
>  
> @@ -727,6 +753,11 @@ static int da9062_i2c_remove(struct i2c_client *i2c)
>  {
>  	struct da9062 *chip = i2c_get_clientdata(i2c);
>  
> +	if (pm_power_off == da9062_power_off)
> +		pm_power_off = NULL;
> +	if (da9062_i2c_client)
> +		da9062_i2c_client = NULL;
> +
>  	mfd_remove_devices(chip->dev);
>  	regmap_del_irq_chip(i2c->irq, chip->regmap_irq);
>  

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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