linux-kernel - Re: [RESEND PATCH v3 3/3] regulator: mcp16502: add regulator driver for MCP16502

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Date:   Wed, 12 Dec 2018 08:01:07 +0000
From:   <Andrei.Stefanescu@...rochip.com>
To:     <broonie@...nel.org>
CC:     <robh+dt@...nel.org>, <lgirdwood@...il.com>,
        <mark.rutland@....com>, <gregkh@...uxfoundation.org>,
        <Cristian.Birsan@...rochip.com>, <Nicolas.Ferre@...rochip.com>,
        <Claudiu.Beznea@...rochip.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [RESEND PATCH v3 3/3] regulator: mcp16502: add regulator driver
 for MCP16502

Hi Mark,

Thank you for the review.

> SPDX headers need to be C++ comments - please make the entire comment
> block a C++ one so it looks more intentional.
I sent a new patch (v4) with the modified comment.
>> +#ifdef CONFIG_SUSPEND
>> +static int mcp16502_suspend(struct device *dev)
>> +{
>> +	struct i2c_client *client = to_i2c_client(dev);
>> +	struct mcp16502 *mcp = i2c_get_clientdata(client);
>> +
>> +	mcp16502_gpio_set_mode(mcp, MCP16502_OPMODE_LPM);
>> +
>> +	return 0;
>> +}
> This puts the device into low power mode when the suspend function gets
> called but this might not be safe - devices using the regulator may not
> be suspended yet so could still need full regulation.  Normally a GPIO
> triggered transition like this would be being done by hardware as part
> of the process of suspending the SoC.  Is there some reason to do this
> manually?
There is a line from the MPU (SHDN) which goes low only when the MPU
turns off. That line is already connected to the PMIC and it differentiates
between suspend-to-mem and standby. To switch to low-power, the PMIC must
be controlled by the GPIO pin LPM.

The suspend sequence is:
- LPM pin goes high (PMIC enters Low-Power <-> Linux standby)
- SHDN goes low (if target suspend state is mem) and then PMIC enters 
HIBERNATE


Best regards,
Andrei