linux-kernel - Re: [PATCH v7 14/33] crypto: rockchip: handle reset also in PM

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Message-ID: <Yr24g3LoO5uFuCux@Red>
Date:   Thu, 30 Jun 2022 16:51:47 +0200
From:   LABBE Corentin <clabbe@...libre.com>
To:     John Keeping <john@...anate.com>
Cc:     heiko@...ech.de, ardb@...nel.org, herbert@...dor.apana.org.au,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v7 14/33] crypto: rockchip: handle reset also in PM

Le Tue, Jun 21, 2022 at 02:37:35PM +0100, John Keeping a écrit :
> On Tue, Jun 21, 2022 at 10:05:54AM +0200, LABBE Corentin wrote:
> > Le Mon, Jun 20, 2022 at 12:04:24PM +0100, John Keeping a écrit :
> > > On Sun, May 08, 2022 at 06:59:38PM +0000, Corentin Labbe wrote:
> > > > reset could be handled by PM functions.
> > > 
> > > Is there any further rationale for this?
> > > 
> > > After this change there is no longer a guaranteed reset pulse on probe
> > > since the reset control may already be de-asserted.  This is normally
> > > the most important case for a reset as it's the only time when the state
> > > of the hardware is unknown.
> > > 
> > > The original use of devm_add_action_or_reset() seems a bit weird already
> > > since there doesn't seem to be any need to assert reset when the driver
> > > is unloaded.
> > > 
> > 
> > I am not an hw engineer, so my knowledge on reset is low.
> > So why not having a reset pulse on probe is a problem ?
> 
> The point of the reset is to bring the hardware back to a known state.
> Since we don't know what state the hardware will be in following the
> bootloader or previous OS, I think the reset in probe is the only place
> that it is important.
> 
> If this patch isn't fixing anything, I suggest just dropping it.

Thanks for the explanation, I will re-add the reset at probe.