linux-kernel - Re: [PATCH] power: supply: qcom_battmgr: remove bogus do

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Date:   Wed, 1 Mar 2023 11:16:34 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] power: supply: qcom_battmgr: remove bogus do_div()

Hi Linus,

On Tue, Feb 14, 2023 at 02:20:42PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The argument to do_div() is a 32-bit integer, and it was read from a
> 32-bit register so there is no point in doing a 64-bit division on it.
> 
> On 32-bit arm, do_div() causes a compile-time warning here:
> 
> include/asm-generic/div64.h:238:22: error: passing argument 1 of '__div64_32' from incompatible pointer type [-Werror=incompatible-pointer-types]
>   238 |   __rem = __div64_32(&(n), __base); \
>       |                      ^~~~
>       |                      |
>       |                      unsigned int *
> drivers/power/supply/qcom_battmgr.c:1130:4: note: in expansion of macro 'do_div'
>  1130 |    do_div(battmgr->status.percent, 100);
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/power/supply/qcom_battmgr.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/power/supply/qcom_battmgr.c b/drivers/power/supply/qcom_battmgr.c
> index ec31f887184f..de77df97b3a4 100644
> --- a/drivers/power/supply/qcom_battmgr.c
> +++ b/drivers/power/supply/qcom_battmgr.c
> @@ -1126,8 +1126,7 @@ static void qcom_battmgr_sm8350_callback(struct qcom_battmgr *battmgr,
>  			battmgr->info.charge_type = le32_to_cpu(resp->intval.value);
>  			break;
>  		case BATT_CAPACITY:
> -			battmgr->status.percent = le32_to_cpu(resp->intval.value);
> -			do_div(battmgr->status.percent, 100);
> +			battmgr->status.percent = le32_to_cpu(resp->intval.value) / 100;
>  			break;
>  		case BATT_VOLT_OCV:
>  			battmgr->status.voltage_ocv = le32_to_cpu(resp->intval.value);
> -- 
> 2.39.1
> 

Would you be able to take this patch directly? It seems obviously
correctTM, has an ack from Sebastian [1], and without it, 32-bit
allmodconfig builds are broken [2] (the other warning in that log has a
fix on the way to you soon).

[1]: https://lore.kernel.org/20230214220210.cpviycsmcppylkgj@mercury.elektranox.org/
[2]: https://storage.tuxsuite.com/public/clangbuiltlinux/continuous-integration2/builds/2MPmxwvmQ7FdpiMhdQN2ZJhcoUP/build.log

Cheers,
Nathan