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From: Lars-Peter Clausen <lars@metafoo.de>
To: Grazvydas Ignotas <notasas@gmail.com>
Cc: Anton Vorontsov <cbouatmailru@gmail.com>,
	Pali Rohar <pali.rohar@gmail.com>,
	Rodolfo Giometti <giometti@linux.it>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 07/14 v3] bq27x00: Cache battery registers
Date: Mon, 14 Feb 2011 23:14:18 +0100	[thread overview]
Message-ID: <4D59A93A.7090800@metafoo.de> (raw)
In-Reply-To: <AANLkTimn2JYtUSUrJBQKzXrw+URD5n0Y2h7QMaFzKFdY@mail.gmail.com>

On 02/14/2011 10:58 PM, Grazvydas Ignotas wrote:
> On Mon, Feb 14, 2011 at 5:01 AM, Lars-Peter Clausen <lars@metafoo.de> wrote:
>> This patch adds a register cache to the bq27x00 battery driver.
>> Usually multiple, if not all, power_supply properties are queried at once,
>> for example when an uevent is generated. Since some registers are used by
>> multiple properties caching the registers should reduce the number of
>> reads.
>>
>> The cache is valid for 5 seconds this roughly matches the internal update
>> interval of the current register for the bq27000/bq27200.
>>
>> Fast changing properties(*_NOW) which can be obtained by reading a single
>> register are not cached.
>>
>> It will also be used in the follow up patch to check if the battery status
>> has been changed since the last update to emit power_supply_changed events.
>>
>> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
>> ---
>>  drivers/power/bq27x00_battery.c |  271 +++++++++++++++++++++-----------------
>>  1 files changed, 150 insertions(+), 121 deletions(-)
>>
>> diff --git a/drivers/power/bq27x00_battery.c b/drivers/power/bq27x00_battery.c
>> index 44bc76b..dbe3fcb 100644
>> --- a/drivers/power/bq27x00_battery.c
>> +++ b/drivers/power/bq27x00_battery.c
> 
> <snip>
> 
>> -static int bq27x00_battery_current(struct bq27x00_device_info *di)
>> +static int bq27x00_battery_current(struct bq27x00_device_info *di,
>> +       union power_supply_propval *val)
>>  {
>> -       int ret;
>> -       int curr = 0;
>> -       int flags = 0;
>> +       int curr;
>>
>> -       ret = bq27x00_read(di, BQ27x00_REG_AI, &curr, false);
>> -       if (ret) {
>> -               dev_err(di->dev, "error reading current\n");
>> -               return 0;
>> -       }
>> +       if (di->chip == BQ27500)
>> +           curr = bq27x00_read(di, BQ27x00_REG_AI, false);
>> +       else
>> +           curr = di->cache.current_now;
>> +
>> +       if (curr < 0)
>> +               return curr;
> 
> This is wrong, as read function returns negative values for bq27500
> when discharging. That's why read function used to pass value through
> argument before your series (return value was for error code).

I don't think so. The register is 16bit wide and it is read as a unsigned. So
in the non error case bq27x00_read will always return >= 0.
The value is later reinterpreted as a signed 16bit.(See the other lines you
quoted underneath).

Did you experience any actual problem with current being wrong?

> 
> Sorry for not noticing this earlier, I only found this now during testing.
> 
>>
>>        if (di->chip == BQ27500) {
>>                /* bq27500 returns signed value */
>> -               curr = (int)((s16)curr) * 1000;
>> +               val->intval = (int)((s16)curr) * 1000;

- Lars

  reply	other threads:[~2011-02-14 22:14 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-12 19:38 [PATCH v2 00/14] POWER: BQ27x00: New Properties, fixes, bq27000 support Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 01/14] bq27x00: Add type property Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 02/14] bq27x00: Improve temperature property precession Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 03/14] bq27x00: Fix CURRENT_NOW property Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 04/14] bq27x00: Return -ENODEV for properties if the battery is not present Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 05/14] bq27x00: Prepare code for addition of bq27000 platform driver Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 06/14] bq27x00: Add bq27000 support Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 07/14] bq27x00: Cache battery registers Lars-Peter Clausen
2011-02-13 15:14   ` Grazvydas Ignotas
2011-02-13 18:56     ` Lars-Peter Clausen
2011-02-14  3:01   ` [PATCH 07/14 v3] " Lars-Peter Clausen
2011-02-14 21:58     ` Grazvydas Ignotas
2011-02-14 22:14       ` Lars-Peter Clausen [this message]
2011-02-15 11:48         ` Grazvydas Ignotas
2011-02-15 22:39           ` Grazvydas Ignotas
2011-02-21  8:28             ` Lars-Peter Clausen
2011-02-21 14:00               ` Grazvydas Ignotas
2011-02-21 14:49                 ` Lars-Peter Clausen
2011-02-21 21:23                   ` Grazvydas Ignotas
2011-02-12 19:39 ` [PATCH v2 07/14] bq27X00: " Lars-Peter Clausen
2011-02-12 19:52   ` Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 08/14] bq27x00: Poll battery state Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 09/14] bq27x00: Add new properties Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 10/14] bq27x00: Add MODULE_DEVICE_TABLE Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 11/14] bq27x00: Give more specific reports on battery status Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 12/14] bq27x00: Minor cleanups Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 13/14] bq27x00: Cleanup bq27x00_i2c_read Lars-Peter Clausen
2011-02-12 19:39 ` [PATCH 14/14] Ignore -ENODATA errors when generating a uevent Lars-Peter Clausen

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