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

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Message-ID: <6162e560-1b60-4e30-8d1e-210ba9e132cd@axis.com>
Date: Thu, 28 Aug 2025 15:33:32 +0800
From: Jerry Lv <jerrylv@...s.com>
To: "H. Nikolaus Schaller" <hns@...delico.com>,
 Sebastian Reichel <sre@...nel.org>, Jerry Lv <Jerry.Lv@...s.com>
Cc: Pali Rohár <pali@...nel.org>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, letux-kernel@...nphoenux.org,
 stable@...r.kernel.org, kernel@...a-handheld.com, andreas@...nade.info
Subject: Re: [PATCH v2 2/2] power: supply: bq27xxx: restrict no-battery
 detection to bq27000

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