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

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Message-ID: <d604104f-837d-34e2-ac62-261a8ccecfed@oss.qualcomm.com>
Date: Sun, 20 Jul 2025 20:54:02 +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 7/20/2025 8:46 PM, Andrew Lunn wrote:
> On Sat, Jul 19, 2025 at 11:07:47PM +0530, Shivendra Pratap wrote:
>>
>>
>> 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;
> 
> I would hope the compiler/optimiser can figure out from the test the
> line before that this is a safe conversion. So i don't think you need
> a cast.
sure, thanks.
> 
> 	Andrew