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 19:47:17 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Andrew Halaney <ahalaney@...hat.com>, 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 18:57, Manivannan Sadhasivam wrote:
> On Tue, Dec 13, 2022 at 05:54:56PM +0100, Krzysztof Kozlowski wrote:
>> 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.
>>
> 
> I'm not sure how you'd fix it with a _correct_ name here. 

Hm, I assumed that it would be enough if driver name would match device
name. Currently these two are not in sync. Maybe it's not enough when
built as module?

> Also, the id table is
> an overkill since there is only one driver that is making use of it. And
> moreover, there is no definite ID to use.

Every driver with a single device support has usually ID table and it's
not a problem...

Best regards,
Krzysztof