linux-kernel - Re: [PATCH 3/5] mfd: wm5110: Add delay before releasing reset line on cold boot

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Message-ID: <20150316204710.GX28806@sirena.org.uk>
Date:	Mon, 16 Mar 2015 20:47:10 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Cc:	lee.jones@...aro.org, sameo@...ux.intel.com, lgirdwood@...il.com,
	patches@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] mfd: wm5110: Add delay before releasing reset line
 on cold boot

On Mon, Mar 16, 2015 at 06:45:18PM +0000, Charles Keepax wrote:

> I think your suspend example is pretty tricky, we enable the
> regulators for the core_supplies at boot, so I guess we have
> requested that the system never removes those so if it does so
> anyway perhaps that is a system problem? There isn't really

No, there's no guarantee that the current state is maintained over
system suspend - system suspend can turn anything off (at least from an
API point of view).

> That would leave the only possible solution being a hard reset
> during every runtime resume but that makes me very nervous about
> the AoD interrupts as state for those would be lost upon that
> reset.

No, you're guaranteed that the supply will stay on while the system is
running so runtime PM is not an issue - it's system suspend that's an
issue.

> All in all, I really struggle to see what more the driver could
> do here.

As I suggested in my original reply handle system suspend.

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