linux-kernel - Re: [RFC PATCH 3/4] dt-bindings: power: reset: Document arm,psci-vendor-reset

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Date:   Tue, 25 Jul 2023 13:26:46 -0700
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Rob Herring <robh@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Sebastian Reichel <sre@...nel.org>
CC:     Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <kernel@...cinc.com>,
        Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>,
        Melody Olvera <quic_molvera@...cinc.com>,
        "Prasad Sodagudi" <quic_psodagud@...cinc.com>,
        Mukesh Ojha <quic_mojha@...cinc.com>
Subject: Re: [RFC PATCH 3/4] dt-bindings: power: reset: Document
 arm,psci-vendor-reset



On 7/25/2023 11:01 AM, Elliot Berman wrote:
> 
> 
> On 7/24/2023 4:23 PM, Rob Herring wrote:
>> On Mon, Jul 24, 2023 at 03:30:53PM -0700, Elliot Berman wrote:
>>> Add devicetree bindings for using PSCI SYSTEM_RESET2 with vendor 
>>> reset  types.
>>>
>>> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
>>> ---
>>>   .../power/reset/arm,psci-vendor-reset.yaml    | 35 +++++++++++++++++++
>>>   MAINTAINERS                                   |  1 +
>>>   2 files changed, 36 insertions(+)
>>>   create mode 100644 
>>> Documentation/devicetree/bindings/power/reset/arm,psci-vendor-reset.yaml
>>>
>>> diff --git 
>>> a/Documentation/devicetree/bindings/power/reset/arm,psci-vendor-reset.yaml b/Documentation/devicetree/bindings/power/reset/arm,psci-vendor-reset.yaml
>>> new file mode 100644
>>> index 000000000000..18b0b8c167a1
>>> --- /dev/null
>>> +++ 
>>> b/Documentation/devicetree/bindings/power/reset/arm,psci-vendor-reset.yaml
>>> @@ -0,0 +1,35 @@
>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>> +# Copyright 2023 Qualcomm Innovation Center, Inc. All Rights Reserved.
>>> +%YAML 1.2
>>> +---
>>> +$id: 
>>> http://devicetree.org/schemas/power/reset/arm,psci-vendor-reset.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: PSCI SYSTEM_RESET2 Vendor Resets
>>> +
>>> +maintainers:
>>> +  - Elliot Berman <quic_eberman@...cinc.com>
>>> +
>>> +description: |
>>> +  PSCI SYSTEM_RESET2 supports vendor-defined reset types. This 
>>> describes
>>> +  the conversion of reboot modes to the reset types.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: arm,psci-vendor-reset
>>> +
>>> +allOf:
>>> +  - $ref: reboot-mode.yaml#
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    firmware {
>>> +      psci-vendor-resets {
>>> +        compatible = "arm,psci-vendor-reset";
>>
>> We already have a node for PSCI, we don't need a second one. You can
>> have a separate driver without a separate node.
>>
> 
> I could also place the reboot-mode functionality straight into 
> drivers/firwmare/psci/? I thought that might be more controversial than 
> separate driver, but maybe not?
> 
> Mark/Loreno, do you have any concerns to add the reboot-mode driver 
> functionality directly in drivers/firmware/psci/psci.c?
> 
> Sebastian, do you have any concerns to have this reboot-mode driver 
> outside drivers/power/reset/?
> 

Sebastian, please disregard this question.

Mukesh pointed out that reboot-mode framework isn't the right option 
here since this driver does the actual reset and, as I understand, 
reboot-mode isn't intended to do actual reset. I'm going to implement 
something similar to what reboot-mode framework does but register 
against the restart_handler_list instead of reboot_notifier_list.

>>> +        reboot-normal = <0x100>;
>>
>> Wouldn't 'normal' be the normal PSCI reset?
>>
> 
> Ah, right. I had my head buried in the reboot-mode code when creating 
> the example. I can remove from the example.
> 
>>> +        reboot-bootloader = <0x101>;
>>> +        reboot-fastboot = <0x102>;
>>> +      };
>>> +    };
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index d516295978a4..2da4c5f1917b 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -16982,6 +16982,7 @@ M:    Mark Rutland <mark.rutland@....com>
>>>   M:    Lorenzo Pieralisi <lpieralisi@...nel.org>
>>>   L:    linux-arm-kernel@...ts.infradead.org (moderated for 
>>> non-subscribers)
>>>   S:    Maintained
>>> +F:    
>>> Documentation/devicetree/bindings/power/reset/arm,psci-vendor-reset.yaml
>>>   F:    drivers/firmware/psci/
>>>   F:    include/linux/psci.h
>>>   F:    include/uapi/linux/psci.h
>>> -- 
>>> 2.41.0
>>>