linux-kernel - Re: [PATCH 1/1] regulators: bd718x7: Add enable times

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Message-ID: <beba25e85db20649aa040fc0ae549895c9265f6f.camel@fi.rohmeurope.com>
Date:   Thu, 17 Dec 2020 14:21:46 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     "guido.gunther@...i.sm" <guido.gunther@...i.sm>
CC:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        linux-power <linux-power@...rohmeurope.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "angus.ainslie@...i.sm" <angus.ainslie@...i.sm>
Subject: Re: [PATCH 1/1] regulators: bd718x7: Add enable times


On Wed, 2020-12-16 at 13:41 +0100, Guido Günther wrote:
> Hi Matti,
> On Wed, Dec 16, 2020 at 12:29:20PM +0000, Vaittinen, Matti wrote:
> > Hello Guido,
> > 
> > Thanks for looking at this!
> > 
> > On Wed, 2020-12-16 at 12:05 +0100, Guido Günther wrote:
> > > Use the typical startup times from the data sheet so boards get a
> > > reasonable default. Not setting any enable time can lead to board
> > > hangs
> > > when e.g. clocks are enabled too soon afterwards.
> > > 
> > > This fixes gpu power domain resume on the Librem 5.
> > > 
> > > Signed-off-by: Guido Günther <agx@...xcpu.org>
> > > ---
> > >  drivers/regulator/bd718x7-regulator.c | 27
> > > +++++++++++++++++++++++++++
> > >  1 file changed, 27 insertions(+)
> > > 
> > > diff --git a/drivers/regulator/bd718x7-regulator.c
> > > b/drivers/regulator/bd718x7-regulator.c
> > > index e6d5d98c3cea..d6d34aa4ee2e 100644
> > > --- a/drivers/regulator/bd718x7-regulator.c
> > > +++ b/drivers/regulator/bd718x7-regulator.c
> > > @@ -613,6 +613,7 @@ static struct bd718xx_regulator_data
> > > bd71847_regulators[] = {
> > >  			.vsel_mask = DVS_BUCK_RUN_MASK,
> > >  			.enable_reg = BD718XX_REG_BUCK1_CTRL,
> > >  			.enable_mask = BD718XX_BUCK_EN,
> > > +			.enable_time = 144,
> > 
> > Where are these values obtained from? I have a feeling they might
> > be
> > board / load specific. If this is the case - can the "regulator-
> > enable-
> > ramp-delay" from device-tree be used instead to avoid hard-coding
> > board
> > specific values in the driver? Although, sane defaults would
> > probably
> > not be a bad idea - if I read code correctly then the constrains
> > from
> > DT can be used to override these values.
> 
> They're the 'typical values' from the data sheet and it's basically
> all
> about setting a default for "regulator-enable-ramp-delay" to avoid
> having every board do the same. If that's not the right thing todo
> let
> me know and i add these to each of our boards (which is where i
> basically started from but then figured that this would be busywork
> and every board would hit that problem).
> 
> > I'd prefer well named defines over raw numeric values though.
> 
> So s.th. like
> 
> BD71837_BUCK1_STARTUP_TIME 144
> 
> (using the terminology from the datasheet)? If that works I'll send a
> v2.

Just noticed I never replied. Sorry. This looks good to me!

Best Regards
  --Matti