linux-kernel - Re: [PATCH v14 03/10] power: reset: reboot-mode: Add support for 64 bit magic

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Message-ID: <b4e26633-b892-fda1-4738-5c8aa85d71d1@oss.qualcomm.com>
Date: Tue, 2 Sep 2025 15:25:53 +0530
From: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
To: Casey Connolly <casey.connolly@...aro.org>,
        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>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.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 v14 03/10] power: reset: reboot-mode: Add support for 64
 bit magic



On 8/28/2025 6:52 PM, Casey Connolly wrote:
> Hi Shivendra,
> 
> On 15/08/2025 16:35, Shivendra Pratap wrote:
>> Current reboot-mode supports a single 32-bit argument for any
>> supported mode. Some reboot-mode based drivers may require
>> passing two independent 32-bit arguments during a reboot
>> sequence, for uses-cases, where a mode requires an additional
>> argument. Such drivers may not be able to use the reboot-mode
>> driver. For example, ARM PSCI vendor-specific resets, need two
>> arguments for its operation – reset_type and cookie, to complete
>> the reset operation. If a driver wants to implement this
>> firmware-based reset, it cannot use reboot-mode framework.
>>
>> Introduce 64-bit magic values in reboot-mode driver to
>> accommodate dual 32-bit arguments when specified via device tree.
>> In cases, where no second argument is passed from device tree,
>> keep the upper 32-bit of magic un-changed(0) to maintain backward
>> compatibility.
> 
> How about adding a n_magic_args property to struct reboot_mode_driver?
> Then in struct mode_info change magic to be a u32 array of a fixed
> length (currently two in-keeping with the DT bindings).
> 
> Parsing the DT values then gets simpler (u32_array) and the magic value
> can be passed into the ->write() cb as a pointer since all the
> reboot_mode drivers already know how big the array is. Unpopulated DT
> values would just be 0.


sure. Will convert it to u32 magic[2] and ->write can now pass
"u32*" and can be de-referenced by the using driver.

Could not understand that how we want to use n_magic_args and who shall
set it? Do we statically define it to two for now? or should we skip
n_magic_args for now?

thanks,
Shivendra