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

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Message-ID: <524C124C.5050102@nvidia.com>
Date:	Wed, 2 Oct 2013 18:02:12 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Axel Lin <axel.lin@...ics.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

On Wednesday 02 October 2013 05:26 PM, Axel Lin wrote:
> 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),
>

For this, it need to change for all entry:

The voltage select bits set the DC/DC output voltage level and power the 
DC/DC converter down.
   ....00h : DC/DC powered down
   01h-40h : V_SD2=0.6V+sd2_vsel*12.5mV
   41h-70h : V_SD2=1.4V+(sd2_vsel-40h)*25mV
   71h-7Fh : V_SD2=2.6V+(sd2_vsel-70h)*50mV

Again second and third entry need to be taken care.
Third entry min_uV is completely wrong here. Did not get caught in my 
testing as I did not have requirement of the third range in my board.

static const struct regulator_linear_range as3722_sd2345_ranges[] = {
         regulator_lin_range(0x01, 0x40,  600000, 12500),
         regulator_lin_range(0x41, 0x70, 1400000, 25000),
         regulator_lin_range(0x71, 0x7F, 1725000, 50000),
};


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