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

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Message-ID: <20221219135046.GA126558@thinkpad>
Date:   Mon, 19 Dec 2022 19:20:46 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...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 Tue, Dec 13, 2022 at 07:47:17PM +0100, Krzysztof Kozlowski wrote:
> 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?
> 

Right, for module it is not enough and that's why we need id_table/alias.

> > 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...
> 

Are you referring to OF/ACPI ID table? Or something else?

Thanks,
Mani

> Best regards,
> Krzysztof
> 

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