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Date: Tue, 13 Jun 2023 13:54:51 -0700
From: Elliot Berman <quic_eberman@...cinc.com>
To: Mark Rutland <mark.rutland@....com>
CC: Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Sudeep Holla <sudeep.holla@....com>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
Trilok Soni <quic_tsoni@...cinc.com>,
"Prasad Sodagudi (QUIC)" <quic_psodagud@...cinc.com>,
<quic_collinsd@...cinc.com>,
Melody Olvera <quic_molvera@...cinc.com>
Subject: Re: [PATCH v3 1/3] dt: psci: Add arm,psci-sys-reset2-vendor-param
property
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@....com>
>> Signed-off-by: Elliot Berman <eberman@...eaurora.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@....com>
> To: Elliot Berman <eberman@...eaurora.org>
> Subject: Re: [PATCH v3 1/3] dt: psci: Add arm,psci-sys-reset2-vendor-param
> property
> Message-ID: <20200320120105.GA36658@...TD0UTHF1T.local>
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> Cc: Trilok Soni <tsoni@...eaurora.org>,
> Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
> David Collins <collinsd@...eaurora.org>, linux-arm-msm@...r.kernel.org,
> linux-kernel@...r.kernel.org, Bjorn Andersson <bjorn.andersson@...aro.org>,
> Sudeep Holla <sudeep.holla@....com>, Prasad Sodagudi <psodagud@...eaurora.org>,
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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@....com>
>> Signed-off-by: Elliot Berman <eberman@...eaurora.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@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
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