linux-kernel - Re: [Letux-kernel] [PATCH v2 2/2] power: supply: bq27xxx: restrict no-battery detection to bq27000

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Message-Id: <2CE9A923-2205-425D-81D0-DAFF8527C498@goldelico.com>
Date: Thu, 28 Aug 2025 13:45:47 +0200
From: "H. Nikolaus Schaller" <hns@...delico.com>
To: Discussions about the Letux Kernel <letux-kernel@...nphoenux.org>
Cc: Sebastian Reichel <sre@...nel.org>,
 Jerry Lv <Jerry.Lv@...s.com>,
 linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 stable@...r.kernel.org,
 kernel@...a-handheld.com,
 Pali Rohár <pali@...nel.org>,
 Discussions about the Letux Kernel <letux-kernel@...nphoenux.org>,
 Andreas Kemnade <andreas@...nade.info>
Subject: Re: [Letux-kernel] [PATCH v2 2/2] power: supply: bq27xxx: restrict
 no-battery detection to bq27000



> Am 28.08.2025 um 09:33 schrieb Jerry Lv <jerrylv@...s.com>:
> 
> On 8/23/2025 6:34 PM, H. Nikolaus Schaller wrote:
>> There are fuel gauges in the bq27xxx series (e.g. bq27z561) which may in some
>> cases report 0xff as the value of BQ27XXX_REG_FLAGS that should not be
>> interpreted as "no battery" like for a disconnected battery with some built
>> in bq27000 chip.
>> 
>> So restrict the no-battery detection originally introduced by
>> 
>>     commit 3dd843e1c26a ("bq27000: report missing device better.")
>> 
>> to the bq27000.
>> 
>> There is no need to backport further because this was hidden before
>> 
>> 	commit f16d9fb6cf03 ("power: supply: bq27xxx: Retrieve again when busy")
>> 
>> Fixes: f16d9fb6cf03 ("power: supply: bq27xxx: Retrieve again when busy")
>> Suggested-by: Jerry Lv <Jerry.Lv@...s.com>
>> Cc: stable@...r.kernel.org
>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>> ---
>>  drivers/power/supply/bq27xxx_battery.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/power/supply/bq27xxx_battery.c b/drivers/power/supply/bq27xxx_battery.c
>> index dadd8754a73a8..3363af24017ae 100644
>> --- a/drivers/power/supply/bq27xxx_battery.c
>> +++ b/drivers/power/supply/bq27xxx_battery.c
>> @@ -1944,8 +1944,8 @@ static void bq27xxx_battery_update_unlocked(struct bq27xxx_device_info *di)
>>  	bool has_singe_flag = di->opts & BQ27XXX_O_ZERO;
>>    	cache.flags = bq27xxx_read(di, BQ27XXX_REG_FLAGS, has_singe_flag);
>> -	if ((cache.flags & 0xff) == 0xff)
>> -		cache.flags = -ENODEV; /* read error */
>> +	if (di->chip == BQ27000 && (cache.flags & 0xff) == 0xff)
>> +		cache.flags = -ENODEV; /* bq27000 hdq read error */
>>  	if (cache.flags >= 0) {
>>  		cache.capacity = bq27xxx_battery_read_soc(di);
>>  
> 
> This change works fine for BQ27z561

Thanks for testing!

So it appears we need a maintainer to pick up these patches...

BR,
Nikolaus