linux-kernel - Re: [PATCH v2 00/13] Qcom: LLCC/EDAC: Fix base address used for LLCC banks

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Date:   Tue, 13 Dec 2022 17:54:56 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Andrew Halaney <ahalaney@...hat.com>
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
Subject: Re: [PATCH v2 00/13] Qcom: LLCC/EDAC: Fix base address used for LLCC
 banks

On 13/12/2022 06:28, Manivannan Sadhasivam wrote:
> On Mon, Dec 12, 2022 at 01:23:40PM -0600, Andrew Halaney wrote:
>> On Mon, Dec 12, 2022 at 06:02:58PM +0530, Manivannan Sadhasivam wrote:
>>> The Qualcomm LLCC/EDAC drivers were using a fixed register stride for
>>> accessing the (Control and Status Regsiters) CSRs of each LLCC bank.
>>> This offset only works for some SoCs like SDM845 for which driver support
>>> was initially added.
>>>
>>> But the later SoCs use different register stride that vary between the
>>> banks with holes in-between. So it is not possible to use a single register
>>> stride for accessing the CSRs of each bank. By doing so could result in a
>>> crash with the current drivers. So far this crash is not reported since
>>> EDAC_QCOM driver is not enabled in ARM64 defconfig and no one tested the
>>> driver extensively by triggering the EDAC IRQ (that's where each bank
>>> CSRs are accessed).
>>>
>>> For fixing this issue, let's obtain the base address of each LLCC bank from
>>> devicetree and get rid of the fixed stride.
>>>
>>> This series affects multiple platforms but I have only tested this on
>>> SM8250 and SM8450. Testing on other platforms is welcomed.
>>>
>>
>> Tested-by: Andrew Halaney <ahalaney@...hat.com> # sa8540p-ride
>>
> 
> Thanks!
> 
>> I took this for a quick spin on the qdrive3 I've got access to without
>> any issue:
>>
>>     [root@...alhost ~]# modprobe qcom_edac
>>     [root@...alhost ~]# dmesg | grep -i edac
>>     [    0.620723] EDAC MC: Ver: 3.0.0
>>     [    1.165417] ghes_edac: GHES probing device list is empty
>>     [  594.688103] EDAC DEVICE0: Giving out device to module qcom_llcc_edac controller llcc: DEV qcom_llcc_edac (INTERRUPT)
>>     [root@...alhost ~]# cat /proc/interrupts | grep ecc
>>     174:          0          0          0          0          0          0          0          0     GICv3 614 Level     llcc_ecc
>>     [root@...alhost ~]#
>>
>> Potentially stupid question, but are users expected to manually load the
>> driver as I did? I don't see how it would be loaded automatically in the
>> current state, but thought it was funny that I needed to modprobe
>> myself.
>>
>> Please let me know if you want me to do any more further testing!
>>
> 
> Well, I always ended up using the driver as a built-in. I do make it module for
> build test but never really used it as a module, so didn't catch this issue.
> 
> This is due to the module alias not exported by the qcom_edac driver. Below
> diff allows kernel to autoload it:
> 
> diff --git a/drivers/edac/qcom_edac.c b/drivers/edac/qcom_edac.c
> index f7afb5375293..13919d01c22d 100644
> --- a/drivers/edac/qcom_edac.c
> +++ b/drivers/edac/qcom_edac.c
> @@ -419,3 +419,4 @@ module_platform_driver(qcom_llcc_edac_driver);
>  
>  MODULE_DESCRIPTION("QCOM EDAC driver");
>  MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:qcom_llcc_edac");

While this is a way to fix it, but instead of creating aliases for wrong
names, either a correct name should be used or driver should receive ID
table.

Best regards,
Krzysztof