From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: "Pali Rohár" <pali.rohar@gmail.com>
Cc: Anton Vorontsov <anton@enomsg.org>,
linux-kernel@vger.kernel.org,
David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH] bq2415x_charger: fix max battery regulation voltage
Date: Tue, 15 Oct 2013 16:54:14 +0200 [thread overview]
Message-ID: <525D5716.2000109@free-electrons.com> (raw)
In-Reply-To: <201310151556.23557@pali>
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On 15/10/2013 15:56, Pali Rohár wrote:
> On Wednesday 02 October 2013 12:24:22 Alexandre Belloni wrote:
>> As per the datasheets, maximum battery regulation voltage is
>> 4440mV.
>>
>> The formula is (voltage - offset) / step, so the maximum value
>> is: (4440 - 3500) / 20 = 47
>>
>> Signed-off-by: Alexandre Belloni
>> <alexandre.belloni@free-electrons.com> ---
>> drivers/power/bq2415x_charger.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/power/bq2415x_charger.c
>> b/drivers/power/bq2415x_charger.c index 0727f92..0aa643e
>> 100644
>> --- a/drivers/power/bq2415x_charger.c
>> +++ b/drivers/power/bq2415x_charger.c
>> @@ -607,7 +607,7 @@ static int
>> bq2415x_set_battery_regulation_voltage(struct bq2415x_device
>> *bq,
>>
>> if (val < 0)
>> val = 0;
>> - else if (val > 94) /* FIXME: Max is 94 or 122 ? Set max
>> value ? */ + else if (val > 47)
>> return -EINVAL;
>>
>> return bq2415x_i2c_write_mask(bq, BQ2415X_REG_VOLTAGE, val,
>
> Right, max is 47 (101111) and not 94 (1011110). But if you set
> all six registers to 1 then you get 63 (111111) and not 122.
>
> I do not know from where I got above bad values, but you should
> add comment to code that according to datasheet max value is
> 4440mV (101111) and not 4760mV (111111).
>
You probably missed the division by 2. BTW, I much prefer int val = (mV
- 3500) / 20;
which is clearer: offset is 3500mV and step is 20mV. I find your
calculation quite weird ;)
I'll send V2 with a comment then. Thank you for your review.
- --
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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next prev parent reply other threads:[~2013-10-15 14:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-02 10:24 Alexandre Belloni
2013-10-15 13:56 ` Pali Rohár
2013-10-15 14:54 ` Alexandre Belloni [this message]
2013-10-16 14:08 Alexandre Belloni
2013-10-16 14:09 ` Alexandre Belloni
2013-10-25 23:25 ` Anton Vorontsov
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