linux-kernel - Re: [PATCH 17/24] arm64: dts: qcom: glymur-crd: Avoid RTC probe failure

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Message-ID: <49004d3e-7914-48ee-8705-ee86d1944166@oss.qualcomm.com>
Date: Tue, 14 Oct 2025 12:23:23 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
        Pankaj Patil <pankaj.patil@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 17/24] arm64: dts: qcom: glymur-crd: Avoid RTC probe
 failure

On 10/13/25 1:04 PM, Kamal Wadhwa wrote:
> On Mon, Oct 06, 2025 at 04:28:59PM +0200, Konrad Dybcio wrote:
>> On 10/1/25 2:23 PM, Kamal Wadhwa wrote:
>>> Hi Krzysztof,
>>>
>>> On Thu, Sep 25, 2025 at 1:41 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>>>
>>>> On Thu, 25 Sept 2025 at 15:34, Pankaj Patil
>>>> <pankaj.patil@....qualcomm.com> wrote:
>>>>>
>>>>> From: Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>
>>>>>
>>>>> On Glymur boards, the RTC alarm interrupts are routed to SOCCP
>>>>> subsystems and are not available to APPS. This can cause the
>>>>> RTC probe failure as the RTC IRQ registration will fail in
>>>>> probe.
>>>>>
>>>>> Fix this issue by adding `no-alarm` property in the RTC DT
>>>>> node. This will skip the RTC alarm irq registration and
>>>>> the RTC probe will return success.
>>>>
>>>>
>>>> This is ridiculous. You just added glymur CRD and you claim now that
>>>> it's broken and you need to fix it. So just fix that commit!
>>>
>>> I'm afraid, but this is an actual limitation we have for Glymur
>>> (compared to Kaanapali).
>>> The RTC is part of the pmk8850.dtsi that is common between Kaanapali and
>>> Glymur. On Glymur (unlike Kaanapali) the APPS processor does *not* have the RTC
>>> IRQ permission for the RTC peripheral.
>>
>> This is interesting.. is that a physical limitation, or some sort of
>> a software security policy?
> 
> This is mostly a limitation for all compute targets(like Glymur). On compute
> targets we need to support ACPI TAD feature[1] this feature uses the RTC alarm.
> In a nutshell, this feature implements 2 times - AC ( adaptor power) and
> DC (battery power) timers, and based on active power source(AC or DC?) at the
> time of timer expiry device will either go for a full bootup or stay in power
> down.
> 
> This feature is implemented on a different subsystem (SoCCP subsystem), and
> since the SPMI `IRQ` permissions can only be assigned to only one subsystem,
> so we can't use the alarms on APPS. This is why we use no-alarms DT to register
> RTC device without alarm-irq support.
> 
> [1] TAD specification - https://uefi.org/sites/default/files/resources/ACPI_5.pdf
> section 9.18

Hm, is there maybe some sort of an interface to talk to the SoCCP
and set the RTC as we wish, from the OS?

Konrad