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Message-ID: <978b0335-ae9d-7d7a-ad70-6861d6dfcc43@linaro.org>
Date:   Wed, 18 Jan 2023 18:06:50 +0100
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Subject: Re: [PATCH v6 17/17] soc: qcom: llcc: Do not create EDAC platform
 device on SDM845
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To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc:     andersson@kernel.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, bp@alien8.de,
        tony.luck@intel.com, quic_saipraka@quicinc.com,
        konrad.dybcio@linaro.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org, james.morse@arm.com,
        mchehab@kernel.org, rric@kernel.org, linux-edac@vger.kernel.org,
        quic_ppareek@quicinc.com, luca.weiss@fairphone.com,
        ahalaney@redhat.com, steev@kali.org, stable@vger.kernel.org
References: <20230118150904.26913-1-manivannan.sadhasivam@linaro.org>
 <20230118150904.26913-18-manivannan.sadhasivam@linaro.org>
 <d3cd9b7a-6286-a140-d205-6d4b6ca8092d@linaro.org>
 <20230118155919.GD4690@thinkpad>
 <3ca41414-df2e-4ba0-9dc7-cacea2413fe6@linaro.org>
 <20230118162657.GE4690@thinkpad>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20230118162657.GE4690@thinkpad>
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On 18/01/2023 17:26, Manivannan Sadhasivam wrote:
> On Wed, Jan 18, 2023 at 05:05:28PM +0100, Krzysztof Kozlowski wrote:
>> On 18/01/2023 16:59, Manivannan Sadhasivam wrote:
>>> On Wed, Jan 18, 2023 at 04:37:29PM +0100, Krzysztof Kozlowski wrote:
>>>> On 18/01/2023 16:09, Manivannan Sadhasivam wrote:
>>>>> The platforms based on SDM845 SoC locks the access to EDAC registers in the
>>>>> bootloader. So probing the EDAC driver will result in a crash. Hence,
>>>>> disable the creation of EDAC platform device on all SDM845 devices.
>>>>>
>>>>> The issue has been observed on Lenovo Yoga C630 and DB845c.
>>>>>
>>>>> Cc: <stable@vger.kernel.org> # 5.10
>>>>> Reported-by: Steev Klimaszewski <steev@kali.org>
>>>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>>>>> ---
>>>>>  drivers/soc/qcom/llcc-qcom.c | 17 ++++++++++++-----
>>>>>  1 file changed, 12 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
>>>>> index 7b7c5a38bac6..8d840702df50 100644
>>>>> --- a/drivers/soc/qcom/llcc-qcom.c
>>>>> +++ b/drivers/soc/qcom/llcc-qcom.c
>>>>> @@ -1012,11 +1012,18 @@ static int qcom_llcc_probe(struct platform_device *pdev)
>>>>>  
>>>>>  	drv_data->ecc_irq = platform_get_irq_optional(pdev, 0);
>>>>>  
>>>>> -	llcc_edac = platform_device_register_data(&pdev->dev,
>>>>> -					"qcom_llcc_edac", -1, drv_data,
>>>>> -					sizeof(*drv_data));
>>>>> -	if (IS_ERR(llcc_edac))
>>>>> -		dev_err(dev, "Failed to register llcc edac driver\n");
>>>>> +	/*
>>>>> +	 * The platforms based on SDM845 SoC locks the access to EDAC registers
>>>>> +	 * in bootloader. So probing the EDAC driver will result in a crash.
>>>>> +	 * Hence, disable the creation of EDAC platform device on SDM845.
>>>>> +	 */
>>>>> +	if (!of_device_is_compatible(dev->of_node, "qcom,sdm845-llcc")) {
>>>>
>>>> Don't spread of_device_is_compatible() in driver code. You have driver
>>>> data for this.
>>>>
>>>
>>> Yeah, but there is no ID to in the driver data to identify an SoC. 
>>
>> What do you mean there is no? You use exactly the same compatible as the
>> one in driver data.
>>
> 
> Right, but I was saying that there is no unique field to identify an SoC.
> 
>>
>>> I could add
>>> one but is that really worth doing so? Is using of_device_is_compatible() in
>>> drivers discouraged nowadays?
>>
>> Because it spreads variant matching all over. It does not scale. drv
>> data fields are the way or better quirks/flags.
>>
> 
> The driver quirk/flags are usually beneficial if it applies to multiple
> platforms, otherwise they are a bit overkill IMO just like in this case.
> 
> One can argue that this matching could spread to other SoCs in the future, but
> I don't think that could happen for this case.

That's the argument for every flag/quirk/field. Driver already uses it -
see need_llcc_cfg being set for only one (!!!) variant. Now you add
orthogonal field just as of_device_is_compatible(). No, that's why we
have driver data and as I said - it is already used.

Best regards,
Krzysztof