linux-kernel - Re: [PATCH 0/3] Implement vendor resets for PSCI SYSTEM

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Message-ID: <e8670fdb-aa7d-4dc4-ba46-53967f1fe7fb@linaro.org>
Date:   Mon, 20 Nov 2023 18:27:47 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Elliot Berman <quic_eberman@...cinc.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>,
        Melody Olvera <quic_molvera@...cinc.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Florian Fainelli <florian.fainelli@...adcom.com>
Subject: Re: [PATCH 0/3] Implement vendor resets for PSCI SYSTEM_RESET2

On 20/11/2023 17:03, Elliot Berman wrote:
> 
> 
> On 11/20/2023 2:55 AM, Krzysztof Kozlowski wrote:
>> On 17/11/2023 22:18, Elliot Berman wrote:
>>> The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional
>>> reset types which could be mapped to the reboot argument.
>>>
>>> Setting up reboot on Qualcomm devices can be inconsistent from chipset
>>> to chipset.  Generally, there is a PMIC register that gets written to
>>> decide the reboot type. There is also sometimes a cookie that can be
>>> written to indicate that the bootloader should behave differently than a
>>> regular boot. These knobs evolve over product generations and require 
>>> more drivers. Qualcomm firmwares are beginning to expose vendor
>>> SYSTEM_RESET2 types to simplify driver requirements from Linux.
>>>
>>> Add support in PSCI to statically wire reboot mode commands from
>>> userspace to a vendor reset and cookie value using the device tree. The
>>> DT bindings are similar to reboot mode framework except that 2
>>> integers are accepted (the type and cookie). Also, reboot mode framework
>>> is intended to program, but not reboot, the host. PSCI SYSTEM_RESET2
>>> does both. I've not added support for reading ACPI tables since I don't
>>> have any device which provides them + firmware that supports vendor
>>> SYSTEM_RESET2 types.
>>>
>>> Previous discussions around SYSTEM_RESET2:
>>> - https://lore.kernel.org/lkml/20230724223057.1208122-2-quic_eberman@quicinc.com/T/
>>> - https://lore.kernel.org/all/4a679542-b48d-7e11-f33a-63535a5c68cb@quicinc.com/
>>
>> Please link here upstream DTS user for this.
> 
> The changes are applicable for SM8650, but hasn't yet landed in arm64/for-next/core.
> 
> I'll include it in the v2 with note.

It's enough if you link to lore or any other upstream-oriented tree with
that user. Does not have to be merged.

Best regards,
Krzysztof