linux-kernel - Re: [PATCH v2 1/3] soc: qcom: llcc: Pass SoC specific EDAC register offsets to EDAC driver

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Date:   Wed, 24 Aug 2022 18:27:59 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Sai Prakash Ranjan <quic_saipraka@...cinc.com>
Cc:     bjorn.andersson@...aro.org, bp@...en8.de, mchehab@...nel.org,
        james.morse@....com, rric@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_tsoni@...cinc.com
Subject: Re: [PATCH v2 1/3] soc: qcom: llcc: Pass SoC specific EDAC register
 offsets to EDAC driver

On Wed, Aug 24, 2022 at 10:43:51AM +0530, Sai Prakash Ranjan wrote:
> On 8/23/2022 9:01 PM, Manivannan Sadhasivam wrote:
> > On Mon, Aug 22, 2022 at 05:29:13PM +0530, Sai Prakash Ranjan wrote:
> > > Hi Mani,
> > > 
> > > On 8/12/2022 11:36 AM, Manivannan Sadhasivam wrote:
> > > > The LLCC EDAC register offsets varies between each SoCs. Until now, the
> > > > EDAC driver used the hardcoded register offsets. But this caused crash
> > > > on SM8450 SoC where the register offsets has been changed.
> > > > 
> > > > So to avoid this crash and also to make it easy to accomodate changes for
> > > > new SoCs, let's pass the SoC specific register offsets to the EDAC driver.
> > > > 
> > > > Currently, two set of offsets are used. One is SM8450 specific and another
> > > > one is common to all SoCs.
> > > > 
> > > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > <snip> ...
> > > 
> > > >    static const struct qcom_llcc_config sm8350_cfg = {
> > > > @@ -309,6 +370,7 @@ static const struct qcom_llcc_config sm8350_cfg = {
> > > >    	.size           = ARRAY_SIZE(sm8350_data),
> > > >    	.need_llcc_cfg	= true,
> > > >    	.reg_offset	= llcc_v1_2_reg_offset,
> > > > +	.edac_reg	= &common_edac_reg,
> > > >    };
> > > >    static const struct qcom_llcc_config sm8450_cfg = {
> > > > @@ -316,6 +378,7 @@ static const struct qcom_llcc_config sm8450_cfg = {
> > > >    	.size           = ARRAY_SIZE(sm8450_data),
> > > >    	.need_llcc_cfg	= true,
> > > >    	.reg_offset	= llcc_v21_reg_offset,
> > > > +	.edac_reg	= &sm8450_edac_reg,
> > > >    };
> > > > 
> > > Can we have LLCC version specific register offsets instead of SoC specific similar to reg_offset callbacks?
> > > For SM8450, it would be llcc_v21_edac_reg and for others llcc_v1_2_edac_reg instead of common_edac_reg.
> > > common_edac_reg is very general and is not exactly common for all, its just common for SoCs with same LLCC.
> > > 
> > I thought about it but I was not sure if rest of the SoCs are using version
> > v1.2. I know that reg_offset uses v1.2 but I was skeptical and hence used the
> > SoC specific offsets.
> > 
> > Can you confirm if rest of the SoCs are using v1.2?
> 
> LLCC versioning follows w.x.y.z format and w and y are major and minor versions based
> on which the naming for reg_offsets is chosen.
> 
> Now in above reg_offsets, llcc_v1_2 is not v1.2, it means v1.0 or v2.0 where 1, 2 is a major version
> and 0 is a minor version. llcc_v21 is actually v2.1 where 2 is a major and 1 is a minor version.
> I know the naming is pretty bad, should probably replace llcc_v1_2 with llcc_v1_0_v2_0 and
> llcc_v21 with llcc_v2_1? Note here minor version is important because SM8350 is v2.0 and uses
> old reg offsets.
> 

Yeah it is confusing. I think we should just use the base LLCC version
that got changed with the previous one and add a comment on top of the
definition. For instance, all of the SoCs before SM8450 should use
llcc_v1_reg_offset since the LLCC version starts from v1.0.0 and SM8450 should
use llcc_v2_1_reg_offset since it supports the LLCC reg offset that got changed
since v2.1.0. Thoughts?

Thanks,
Mani

> So coming to your query now, all other SoCs except SM8450(which uses v2.1) are using LLCC v1.0
> or v2.0, so it is valid to use the same logic as reg_offsets for edac_reg.
> 
> Thanks,
> Sai
> 
> > Thanks,
> > Mani
> > 
> > > Version based is more applicable as multiple SoCs might use same LLCC versions and would reduce SoC specific data
> > > which would be needed for every SoC in case some newer LLCC comes out. I know you could just call sm8450_edac_reg
> > > for lets say sm8550 or so on to reduce duplication but that won't look good.
> > > 
> > > 
> > > Thanks,
> > > Sai
> 

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