linux-kernel - Re: [PATCH] regulator: palmas: set supply

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Date:   Wed, 30 Jun 2021 13:13:07 +0100
From:   Mark Brown <broonie@...nel.org>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        Graeme Gregory <gg@...mlogic.co.uk>,
        Liam Girdwood <lgirdwood@...il.com>,
        Nishanth Menon <nm@...com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com,
        Peter Ujfalusi <peter.ujfalusi@...il.com>
Subject: Re: [PATCH] regulator: palmas: set supply_name after registering the
 regulator

On Tue, Jun 29, 2021 at 10:21:45PM +0200, H. Nikolaus Schaller wrote:

> There seems to be a deadlock in probing:

> 	e.g. ldo3_reg depends on vdds_1v8_main supply
> 	vdds_1v8_main depends on smps7_reg supply
> 	smps7_reg depends on vsys_cobra supply
> 	vsys_cobra depends on nothing

> This would normally lead to a simple chain as you described above. But
> ldo3_reg and smps7_reg share the same driver and can probe successfully or
> fail only in common.

I don't see any deadlock there?  Just a straightforward set of
dependencies.  Anything circular would clearly be a driver bug.

> Now if ldo3_reg defers probe through the new rule, smps7_reg is never
> probed successfully because it is the same driver. Hence vdds_1v8_main can
> not become available. And the Palmas continues to run in boot initialization
> until some driver (MMC) wants to switch voltages or whatever.

The driver should just register all the DCDCs before the LDOs, then
everything will sort itself out.  It's *possible* you might see a system
trying to link things together regulators of the same type but that's
very unusual as it makes the system less efficient.

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