linux-kernel - Re: [PATCH 1/3] arm64: dts: qcom: sm8450: Add qfprom node

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Date: Wed, 29 May 2024 19:42:19 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Bjorn Andersson <andersson@...nel.org>
CC: Konrad Dybcio <konrad.dybcio@...aro.org>, <robh@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] arm64: dts: qcom: sm8450: Add qfprom node



On 5/28/2024 9:07 PM, Bjorn Andersson wrote:
> On Sun, Mar 17, 2024 at 08:21:58PM GMT, Bjorn Andersson wrote:
>> On Thu, Mar 14, 2024 at 10:13:59PM +0530, Mukesh Ojha wrote:
>>> Sorry for the late reply, was on vacation.
>>>
>>> On 3/6/2024 9:24 PM, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 3/6/24 13:26, Mukesh Ojha wrote:
>>>>> Add the qfprom node for sm8450 SoC.
>>>>>
>>>>> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
>>>>> ---
>>>>>    arch/arm64/boot/dts/qcom/sm8450.dtsi | 7 +++++++
>>>>>    1 file changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi
>>>>> b/arch/arm64/boot/dts/qcom/sm8450.dtsi
>>>>> index b86be34a912b..02089a388d03 100644
>>>>> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
>>>>> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
>>>>> @@ -4575,6 +4575,13 @@
>>>>>                };
>>>>>            };
>>>>> +        qfprom: efuse@...c8000 {
>>>>> +            compatible = "qcom,sm8450-qfprom", "qcom,qfprom";
>>>>> +            reg = <0 0x221c8000 0 0x1000>;
>>>>
>>>> Is is really only 0x1000-long? Also, is the base you put
>>>> here the ECC-corrected part (if that still exists)?
>>>
>>> No, its not.
>>>
>>> Entire fuse space is this.
>>> 0x221C0000-0x221Cbfff
>>>
>>> ECC corrected range is this 0x221C2000-0x221C3fff and High level OS
>>
>> That's 0x2000. Does this then also imply that the ECC-corrected values
>> are no longer mapped 1:1 with non-corrected, or why do they differ in
>> size?
>>
>>> does have a access to ECC range however, they are not recommended for
>>> SW usage.
>>>
>>> Above mentioned SW range(4) in the patch is  one and only accessible range
>>> available out of 0-7 SW ranges(0x221C4000-0x221Cbfff with each
>>> size 0x1000) and does not have ECC fuses.
>>>
>>
>> So you're saying that in contrast to other platforms, the 4th software
>> range, dedicated for HLOS, does not have a matching ECC-corrected
>> shadow? If that's the case, then "not recommended for SW usage" sounds
>> wrong.
>>
>>> All the downstream use cases are getting fulfilled with this.
>>>
>>
>> You only need ECC if you're unlucky...
>>
> 
> The patch is either incorrect or the commit message is lacking answers
> to the questions from Konrad and myself.
> 
> Would have appreciated a reply here, but either way I'm marking this as
> "changes requested" and dropping it from the queue.

Apology for coming late on this., it just skipped from my tracking.. 
Frankly, I don't have convincing answer apart from what reason are 
exposed to kernel to read for SoCs like sm8[456]0 , will try to get
the answer soon.

-Mukesh