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

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Date:   Wed, 12 Dec 2018 15:55:02 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Andrei.Stefanescu@...rochip.com
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

On Wed, Dec 12, 2018 at 08:01:07AM +0000, Andrei.Stefanescu@...rochip.com wrote:

> > 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

This feels like it should be being controlled somewhere else, if it's
actually causing a change in the PMIC state it seems like it wants to be
done as late as possible in suspend to minimize the risks.  At the very
least suspend_late() for the driver seems appropriate.

Could you submit a version with this feature at least split out into a
separate patch please so we can apply the rest of the code while this is
discussed?

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