diff mbox series

[v3,1/3] dt: psci: Add arm,psci-sys-reset2-vendor-param property

Message ID 1583435129-31356-2-git-send-email-eberman@codeaurora.org (mailing list archive)
State New, archived
Headers show
Series ARM PSCI: Add support for vendor-specific SYSTEM_RESET2 | expand

Commit Message

Elliot Berman March 5, 2020, 7:05 p.m. UTC 
Some implementors of PSCI may wish to use a different reset type than
SYSTEM_WARM_RESET. For instance, Qualcomm SoCs support an alternate
reset_type which may be used in more warm reboot scenarios than
SYSTEM_WARM_RESET permits (e.g. to reboot into recovery mode).

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Elliot Berman <eberman@codeaurora.org>
---
 Documentation/devicetree/bindings/arm/psci.yaml | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Mark Rutland March 20, 2020, 12:01 p.m. UTC | #1 
Hi Elliot,

On Thu, Mar 05, 2020 at 11:05:27AM -0800, Elliot Berman wrote:
> Some implementors of PSCI may wish to use a different reset type than
> SYSTEM_WARM_RESET. For instance, Qualcomm SoCs support an alternate
> reset_type which may be used in more warm reboot scenarios than
> SYSTEM_WARM_RESET permits (e.g. to reboot into recovery mode).

To be honest, I'm still confused by this series, and I think that these
patches indicate a larger problem that we cannot solve generally (e.g.
on other platofrms and/or with ACPI).

I think the underlying issue is whether the semantics for:

a) Linux's RESET_WARM and RESET_SOFT
b) PSCI's SYSTEM_RESET2 SYSTEM_WARM_RESET

... actually align in practice, which this series suggests is not the
case.

If those don't align, then I think that commit:

  4302e381a870aafb ("firmware/psci: add support for SYSTEM_RESET2")

... is not actually reliable, and not something we can support by
default, and we should rethink the code introduce in that commit.

If (a) and (b) are supposed to align, and the behaviour on your platform
is an erratum, then I think we should treat it as such rather than
adding a property that is open to abuse.

Thoughts?

Thanks,
Mark.

> 
> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
> Signed-off-by: Elliot Berman <eberman@codeaurora.org>
> ---
>  Documentation/devicetree/bindings/arm/psci.yaml | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/psci.yaml b/Documentation/devicetree/bindings/arm/psci.yaml
> index 8ef8542..1a9d2dd 100644
> --- a/Documentation/devicetree/bindings/arm/psci.yaml
> +++ b/Documentation/devicetree/bindings/arm/psci.yaml
> @@ -102,6 +102,13 @@ properties:
>        [1] Kernel documentation - ARM idle states bindings
>          Documentation/devicetree/bindings/arm/idle-states.txt
>  
> +  arm,psci-sys-reset2-vendor-param:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +        Vendor-specific reset type parameter to use for SYSTEM_RESET2 during
> +        a warm or soft reboot. If no value is provided, then architectural
> +        reset type SYSTEM_WARM_RESET is used.
> +
>    "#power-domain-cells":
>      description:
>        The number of cells in a PM domain specifier as per binding in [3].
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
Elliot Berman June 13, 2023, 8:54 p.m. UTC | #2 
Reviving this very old thread. In case folks don't have in their 
mailbox, here is archive link:

https://lore.kernel.org/all/20200320120105.GA36658@C02TD0UTHF1T.local/

On 3/20/2020 5:01 AM, Mark Rutland wrote:
> Hi Elliot,
> 
> On Thu, Mar 05, 2020 at 11:05:27AM -0800, Elliot Berman wrote:
>> Some implementors of PSCI may wish to use a different reset type than
>> SYSTEM_WARM_RESET. For instance, Qualcomm SoCs support an alternate
>> reset_type which may be used in more warm reboot scenarios than
>> SYSTEM_WARM_RESET permits (e.g. to reboot into recovery mode).
> 
> To be honest, I'm still confused by this series, and I think that these
> patches indicate a larger problem that we cannot solve generally (e.g.
> on other platofrms and/or with ACPI).
> 
> I think the underlying issue is whether the semantics for:
> 
> a) Linux's RESET_WARM and RESET_SOFT
> b) PSCI's SYSTEM_RESET2 SYSTEM_WARM_RESET
> 
> ... actually align in practice, which this series suggests is not the
> case.
> 
> If those don't align, then I think that commit:
> 
>    4302e381a870aafb ("firmware/psci: add support for SYSTEM_RESET2")
> 
> ... is not actually reliable, and not something we can support by
> default, and we should rethink the code introduce in that commit.
> 
> If (a) and (b) are supposed to align, and the behaviour on your platform
> is an erratum, then I think we should treat it as such rather than
> adding a property that is open to abuse.
> 
> Thoughts?
> 
I think it's ok for (a) and (b) to align (that invalidates this series). 
PSCI SYSTEM_RESET2 supports vendor-specific reset types and the PSCI 
driver doesn't have any way for these vendor-specific resets to happen.

Would a better way be to export a psci_system_reset2 function? I can 
implement a reboot-mode driver for PSCI system_reset2 for DT-based 
platforms.

Thanks,
Elliot

> Thanks,
> Mark.
> 
>>
>> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
>> Signed-off-by: Elliot Berman <eberman@codeaurora.org>
>> ---
>>   Documentation/devicetree/bindings/arm/psci.yaml | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/psci.yaml b/Documentation/devicetree/bindings/arm/psci.yaml
>> index 8ef8542..1a9d2dd 100644
>> --- a/Documentation/devicetree/bindings/arm/psci.yaml
>> +++ b/Documentation/devicetree/bindings/arm/psci.yaml
>> @@ -102,6 +102,13 @@ properties:
>>         [1] Kernel documentation - ARM idle states bindings
>>           Documentation/devicetree/bindings/arm/idle-states.txt
>>   
>> +  arm,psci-sys-reset2-vendor-param:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description: |
>> +        Vendor-specific reset type parameter to use for SYSTEM_RESET2 during
>> +        a warm or soft reboot. If no value is provided, then architectural
>> +        reset type SYSTEM_WARM_RESET is used.
>> +
>>     "#power-domain-cells":
>>       description:
>>         The number of cells in a PM domain specifier as per binding in [3].
>> -- 
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
> 
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> Date: Fri, 20 Mar 2020 12:01:05 +0000
> From: Mark Rutland <mark.rutland@arm.com>
> To: Elliot Berman <eberman@codeaurora.org>
> Subject: Re: [PATCH v3 1/3] dt: psci: Add arm,psci-sys-reset2-vendor-param
>   property
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> 
> Hi Elliot,
> 
> On Thu, Mar 05, 2020 at 11:05:27AM -0800, Elliot Berman wrote:
>> Some implementors of PSCI may wish to use a different reset type than
>> SYSTEM_WARM_RESET. For instance, Qualcomm SoCs support an alternate
>> reset_type which may be used in more warm reboot scenarios than
>> SYSTEM_WARM_RESET permits (e.g. to reboot into recovery mode).
> 
> To be honest, I'm still confused by this series, and I think that these
> patches indicate a larger problem that we cannot solve generally (e.g.
> on other platofrms and/or with ACPI).
> 
> I think the underlying issue is whether the semantics for:
> 
> a) Linux's RESET_WARM and RESET_SOFT
> b) PSCI's SYSTEM_RESET2 SYSTEM_WARM_RESET
> 
> ... actually align in practice, which this series suggests is not the
> case.
> 
> If those don't align, then I think that commit:
> 
>    4302e381a870aafb ("firmware/psci: add support for SYSTEM_RESET2")
> 
> ... is not actually reliable, and not something we can support by
> default, and we should rethink the code introduce in that commit.
> 
> If (a) and (b) are supposed to align, and the behaviour on your platform
> is an erratum, then I think we should treat it as such rather than
> adding a property that is open to abuse.
> 
> Thoughts?
> 
> Thanks,
> Mark.
> 
>>
>> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
>> Signed-off-by: Elliot Berman <eberman@codeaurora.org>
>> ---
>>   Documentation/devicetree/bindings/arm/psci.yaml | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/psci.yaml b/Documentation/devicetree/bindings/arm/psci.yaml
>> index 8ef8542..1a9d2dd 100644
>> --- a/Documentation/devicetree/bindings/arm/psci.yaml
>> +++ b/Documentation/devicetree/bindings/arm/psci.yaml
>> @@ -102,6 +102,13 @@ properties:
>>         [1] Kernel documentation - ARM idle states bindings
>>           Documentation/devicetree/bindings/arm/idle-states.txt
>>   
>> +  arm,psci-sys-reset2-vendor-param:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description: |
>> +        Vendor-specific reset type parameter to use for SYSTEM_RESET2 during
>> +        a warm or soft reboot. If no value is provided, then architectural
>> +        reset type SYSTEM_WARM_RESET is used.
>> +
>>     "#power-domain-cells":
>>       description:
>>         The number of cells in a PM domain specifier as per binding in [3].
>> -- 
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/arm/psci.yaml b/Documentation/devicetree/bindings/arm/psci.yaml
index 8ef8542..1a9d2dd 100644
--- a/Documentation/devicetree/bindings/arm/psci.yaml
+++ b/Documentation/devicetree/bindings/arm/psci.yaml
@@ -102,6 +102,13 @@  properties:
       [1] Kernel documentation - ARM idle states bindings
         Documentation/devicetree/bindings/arm/idle-states.txt
 
+  arm,psci-sys-reset2-vendor-param:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+        Vendor-specific reset type parameter to use for SYSTEM_RESET2 during
+        a warm or soft reboot. If no value is provided, then architectural
+        reset type SYSTEM_WARM_RESET is used.
+
   "#power-domain-cells":
     description:
       The number of cells in a PM domain specifier as per binding in [3].