linux-kernel - Re: [PATCH v11 2/8] power: reset: reboot-mode: Add support for 64 bit magic

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Message-ID: <1653597d-4d6b-a771-fbd8-c129c630ac0a@oss.qualcomm.com>
Date: Sat, 19 Jul 2025 23:07:47 +0530
From: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Souvik Chakravarty <Souvik.Chakravarty@....com>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Andy Yan <andy.yan@...k-chips.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Konrad Dybcio <konradybcio@...nel.org>,
        cros-qcom-dts-watchers@...omium.org, Vinod Koul <vkoul@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Mukesh Ojha <mukesh.ojha@....qualcomm.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Andre Draszik
 <andre.draszik@...aro.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        Elliot Berman <quic_eberman@...cinc.com>,
        Srinivas Kandagatla <srini@...nel.org>
Subject: Re: [PATCH v11 2/8] power: reset: reboot-mode: Add support for 64 bit
 magic



On 7/19/2025 10:27 PM, Andrew Lunn wrote:
>>>> +static int qcom_pon_reboot_mode_write(struct reboot_mode_driver *reboot, u64 magic)
>>>>  {
>>>>  	struct qcom_pon *pon = container_of
>>>>  			(reboot, struct qcom_pon, reboot_mode);
>>>> @@ -37,7 +36,7 @@ static int qcom_pon_reboot_mode_write(struct reboot_mode_driver *reboot,
>>>>  	ret = regmap_update_bits(pon->regmap,
>>>>  				 pon->baseaddr + PON_SOFT_RB_SPARE,
>>>>  				 GENMASK(7, pon->reason_shift),
>>>> -				 magic << pon->reason_shift);
>>>> +				 ((u32)magic) << pon->reason_shift);
> 
> As a general rule of thumb, code with casts is poor quality code. Try
> to write the code without casts.
> 
> Maybe something like
> 
>       If (magic > MAX_U32)
>       	   return -EINVAL;
> 
>       magic_32 = magic;
sure will update it. And in above, should it be recommended to add a explicit
cast(for any avoiding any compiler complains)?
 like: magic_32 = (u32)magic;
> 
> You might be able to go further, and validate that magic actually fits
> into the field when you consider the << pon->reason_shift.
will add a check to see make sure the value is in range after "<< pon->reason_shift".

- thanks.
> 
> 	Andrew