Re: [RFT][PATCH 2/2] regulator: lm363x: Fix n_voltages setting for lm36274

[Dan Murphy]

Axel

On 6/26/19 10:20 AM, Axel Lin wrote:
> Dan Murphy <dmurphy@xxxxxx> æ 2019å6æ26æ éä äå11:07åéï
> > 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 à 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 Li
> > >
> > > 6.5 V
> > > DISPLAY BIAS POSITIVE OUTPUT (VPOS)
> > > Programmable output voltage
> > > range
> > >
> > >
> > > n <axel.lin@xxxxxxxxxx>
> > > ---
> > >    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
> > >
> > > 6.5 V
> > > DISPLAY BIAS POSITIVE OUTPUT (VPOS)
> > > Programmable output voltage
> > > range
> > 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.

Not sure how you get 6.6v the LDO max is 6.5v.

After 0x32->0x7f maps to 6.5v

000000 = 4 V
000001 = 4.05 V
:
011110 = 5.5 V (Default)
:
110010 = 6.5 V

110011 to 111111 map to 6.5 V <- Should never see 6.6v from LDO

Page 7 of the Datasheet says range is 4v->6.5v

Dan

> Would you mind double check again?