linux-kernel - Re: [PATCH v6 17/17] soc: qcom: llcc: Do not create EDAC platform device on SDM845

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Message-ID: <20230118162657.GE4690@thinkpad>
Date:   Wed, 18 Jan 2023 21:56:57 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, bp@...en8.de,
        tony.luck@...el.com, quic_saipraka@...cinc.com,
        konrad.dybcio@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, james.morse@....com,
        mchehab@...nel.org, rric@...nel.org, linux-edac@...r.kernel.org,
        quic_ppareek@...cinc.com, luca.weiss@...rphone.com,
        ahalaney@...hat.com, steev@...i.org, stable@...r.kernel.org
Subject: Re: [PATCH v6 17/17] soc: qcom: llcc: Do not create EDAC platform
 device on SDM845

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@...r.kernel.org> # 5.10
> >>> Reported-by: Steev Klimaszewski <steev@...i.org>
> >>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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.

Thanks,
Mani

> Best regards,
> Krzysztof
> 

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