linux-kernel - Re: [RFT][PATCH 1/2] regulator: as3722: Fix equation to calculate max_uV in regulator_lin

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Date:	Wed, 2 Oct 2013 19:56:59 +0800
From:	Axel Lin <axel.lin@...ics.com>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	Mark Brown <broonie@...nel.org>,
	Florian Lobmaier <florian.lobmaier@....com>,
	Liam Girdwood <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFT][PATCH 1/2] regulator: as3722: Fix equation to calculate
 max_uV in regulator_lin_range macro

2013/10/2 Laxman Dewangan <ldewangan@...dia.com>:
> On Tuesday 01 October 2013 09:03 PM, Axel Lin wrote:
>>
>> Fix off-by-one in the equation to calculate max_uV.
>>
>> Signed-off-by: Axel Lin <axel.lin@...ics.com>
>> ---
>> Hi,
>> I don't have the datasheet and h/w.
>> Just found this issue while reading the code. (Only compile test).
>>
>> Axel
>>   drivers/regulator/as3722-regulator.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/regulator/as3722-regulator.c
>> b/drivers/regulator/as3722-regulator.c
>> index 16a5d26..c6a1fc6 100644
>> --- a/drivers/regulator/as3722-regulator.c
>> +++ b/drivers/regulator/as3722-regulator.c
>> @@ -441,7 +441,7 @@ static struct regulator_ops as3722_ldo3_extcntrl_ops =
>> {
>>                 .max_sel = _max_sel,                                    \
>>                 .uV_step = _step_uV,                                    \
>>                 .min_uV = _min_uV,                                      \
>> -               .max_uV = _min_uV + (_max_sel - _min_sel + 1) * _step_uV,
>> \
>> +               .max_uV = _min_uV + (_max_sel - _min_sel) * _step_uV,   \
>>         }
>>     static const struct regulator_linear_range as3722_ldo_ranges[] = {
>
> The datasheet says:
>
> The voltage select bits set the LDO output voltage 0.825V...3.3V, 25mV steps
>   ....00h : LDO off
>   01h-24h : V_LDO4=0.8V+ldo4_vsel*25mV
>   25h-3Fh : do not use
>   40h-7Fh : V_LDO4=1.725V+(ldo4_vsel-40h)*25mV
>
> And put the linear range as
> regulator_lin_range(0x01, 0x24,  800000, 25000),
> regulator_lin_range(0x40, 0x7F, 1725000, 25000),
>
>
> So as per datasheet, value 0x24 is equal to 1700mV.
>                                      and 0x7F equal to 3300
>
> I created equation based on first entry which is wrong for second entry and
> your equation is correct for second entry but break first one.
>
> I think your equation is correct with following change:
> regulator_lin_range(0x01, 0x24,  825000, 25000),

Hi Laxman,
Thanks for the review.
And how about the setting for as3722_sd2345_ranges?
How the datasheet says for sd2345?

e.g. Should I change
regulator_lin_range(0x01, 0x40,  600000, 12500),
to
regulator_lin_range(0x01, 0x40,  612500, 12500),


Thanks,
Axel.
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