linux-kernel - Re: [RFT][PATCH 2/2] regulator: lm363x: Fix n

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Date:   Wed, 26 Jun 2019 23:20:28 +0800
From:   Axel Lin <axel.lin@...ics.com>
To:     Dan Murphy <dmurphy@...com>
Cc:     Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFT][PATCH 2/2] regulator: lm363x: Fix n_voltages setting for lm36274

Dan Murphy <dmurphy@...com> 於 2019年6月26日 週三 下午11:07寫道：
>
> Hello
>
> On 6/26/19 8:26 AM, Axel Lin wrote:
> > According to the datasheet http://www.ti.com/lit/ds/symlink/lm36274.pdf:
> > Table 23. VPOS Bias Register Field Descriptions VPOS[5:0]:
> > VPOS voltage (50-mV steps): VPOS = 4 V + (Code × 50 mV), 6.5 V max
> > 000000 = 4 V
> > 000001 = 4.05 V
> > :
> > 011110 = 5.5 V (Default)
> > :
> > 110010 = 6.5 V
> > 110011 to 111111 map to 6.5 V
> >
> > So the LM36274_LDO_VSEL_MAX should be 0b110010 (0x32).
> > The valid selectors are 0 ... LM36274_LDO_VSEL_MAX, n_voltages should be
> > LM36274_LDO_VSEL_MAX + 1. Similarly, the n_voltages should be
> > LM36274_BOOST_VSEL_MAX + 1 for LM36274_BOOST.
> >
> > Fixes: bff5e8071533 ("regulator: lm363x: Add support for LM36274")
> > Signed-off-by: Axel Lin <axel.lin@...ics.com>
> > ---
> >   drivers/regulator/lm363x-regulator.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/regulator/lm363x-regulator.c b/drivers/regulator/lm363x-regulator.c
> > index e4a27d63bf90..4b9f618b07e9 100644
> > --- a/drivers/regulator/lm363x-regulator.c
> > +++ b/drivers/regulator/lm363x-regulator.c
> > @@ -36,7 +36,7 @@
> >
> >   /* LM36274 */
> >   #define LM36274_BOOST_VSEL_MAX              0x3f
> > -#define LM36274_LDO_VSEL_MAX         0x34
> > +#define LM36274_LDO_VSEL_MAX         0x32
>
> This does not seem correct the max number of voltages are 0x34.
>
> The register is zero based so you can have 33 voltage select levels and
> + 1 is 34 total selectors
>
> Liam/Mark correct me if I am incorrect.

>From the datasheet, the maximum voltage 110010 = 6.5 V, the 0b110010 is 0x32.
I know it is 0 based, so .n_voltages     = LM36274_LDO_VSEL_MAX + 1,
(And that coding style is to match the original code.)

With your current code where LM36274_LDO_VSEL_MAX and n_voltages is 0x34,
the maximum voltage will become 400000 + 50000 * 0x34 = 6.6V which
does not match the datasheet.

Would you mind double check again?