linux-kernel - Re: [PATCH v2 03/13] arm64: dts: qcom: sdm845: Fix the base addresses of LLCC banks

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Message-ID: <20221213171356.GD4862@thinkpad>
Date:   Tue, 13 Dec 2022 22:43:56 +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,
        stable@...r.kernel.org
Subject: Re: [PATCH v2 03/13] arm64: dts: qcom: sdm845: Fix the base
 addresses of LLCC banks

On Tue, Dec 13, 2022 at 05:27:45PM +0100, Krzysztof Kozlowski wrote:
> On 12/12/2022 13:33, Manivannan Sadhasivam wrote:
> > The LLCC block has several banks each with a different base address
> > and holes in between. So it is not a correct approach to cover these
> > banks with a single offset/size. Instead, the individual bank's base
> > address needs to be specified in devicetree with the exact size.
> > 
> > Also, let's get rid of reg-names property as it is not needed anymore.
> > The driver is expected to parse the reg field based on index to get the
> > addresses of each LLCC banks.
> > 
> > Cc: <stable@...r.kernel.org> # 5.4
> 
> No, you cannot backport it. You will break users.
> 

If the driver change gets backported, it will break users, isn't it?

> > Fixes: ba0411ddd133 ("arm64: dts: sdm845: Add device node for Last level cache controller")
> > Reported-by: Parikshit Pareek <quic_ppareek@...cinc.com>
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/sdm845.dtsi | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > index 65032b94b46d..683b861e060d 100644
> > --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > @@ -2132,8 +2132,9 @@ uart15: serial@...000 {
> >  
> >  		llcc: system-cache-controller@...0000 {
> >  			compatible = "qcom,sdm845-llcc";
> > -			reg = <0 0x01100000 0 0x31000>, <0 0x01300000 0 0x50000>;
> > -			reg-names = "llcc_base", "llcc_broadcast_base";
> 
> Once property was made required, you cannot remove it. What if other
> bindings user depends on it?
> 
> Please instead keep/update the reg-names and/or mark it as deprecated.
> It must stay in DTS for some time.
> 

Fair enough. I will mark it as deprecated in binding and will keep it in dts.

Thanks,
Mani

> Best regards,
> Krzysztof
> 

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