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

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Message-ID: <39b694e9-3275-43b0-a1af-4e2ef7facda3@quicinc.com>
Date:   Mon, 20 Nov 2023 08:03:01 -0800
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 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.