linux-kernel - Re: [RFC PATCH v2 7/7] arm64: dts: qcom: Add the Inline Crypto Engine nodes

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Message-ID: <ZAr5v/jbd18K5Lug@linaro.org>
Date:   Fri, 10 Mar 2023 11:34:55 +0200
From:   Abel Vesa <abel.vesa@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Eric Biggers <ebiggers@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Bart Van Assche <bvanassche@....org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [RFC PATCH v2 7/7] arm64: dts: qcom: Add the Inline Crypto
 Engine nodes

On 23-03-10 10:27:12, Krzysztof Kozlowski wrote:
> On 10/03/2023 10:21, Abel Vesa wrote:
> >>>>>  			compatible = "qcom,sdm630-sdhci", "qcom,sdhci-msm-v5";
> >>>>>  			reg = <0x0c0c4000 0x1000>,
> >>>>> -			      <0x0c0c5000 0x1000>,
> >>>>> -			      <0x0c0c8000 0x8000>;
> >>>>> -			reg-names = "hc", "cqhci", "ice";
> >>>>> +			      <0x0c0c5000 0x1000>;
> >>>>> +			reg-names = "hc", "cqhci";
> >>>>
> >>>> I believe this will break the ICE on these platforms without valid
> >>>> reason. The commit msg does not explain why you do it or why this is
> >>>> necessary.
> >>>>
> >>>> We already we received comment that we keep breaking Qualcomm platforms
> >>>> all the time and need to keep them in some shape.
> >>>>
> >>>> Also, patchset is non-applicable in current set (breaks users) and
> >>>> neither commit nor cover letter mentions it.
> >>>>
> >>>
> >>> FWIW, I tested this patchset on SDA845, and ICE continues to work fine.
> >>
> >> Really? I clearly see of_find_device_by_node -> "return NULL" and all
> >> old code gone, so ABI is broken. Are you sure you applied patch 1-6 and
> >> ICE was working?
> > 
> > of_qcom_ice_get will return the ICE instance if the consumer node has a
> > qcom,ice property with a phandle for the ICE devicetree node.
> 
> When patches 1-6 are applied, there is no qcom,ice property in DTS. Thus
> I don't consider the test as correct... Even if we skip entire ABI
> discussion the patchset is non-bisectable thus the test was failing to
> detect even that.

Yeah, but that could've been solved easily like I explained yesterday on
irc. But that's not worth getting into anymore as I'll keep legacy working as
I explained.

> 
> > It will
> > return NULL otherwise. SDA845 has such ICE node added by this patch,
> > therefore, it will work. All platforms that have such node will work
> > functionally like before. But I'll take care of the legacy approach as
> > well in v3 (see below).
> 
> At point of patch 6 none of nodes have it. That's the entire point of
> bisectability.
> 
> What's more, if you reverse code and makes DTS patches before driver
> hoping to fix bisectability - do you see ICE working on existing
> platforms? I don't think it so...
> 
> > 
> >>
> >>>
> >>> (Though if I understand the patchset correctly, the ICE clock is no longer
> >>> turned off when the UFS host controller is suspended.  That isn't ideal as it
> >>> wastes power.  I would like that to be fixed.)
> >>>
> >>> Anyway, when you say "break the ICE", do you really mean "make an incompatible
> >>> change to the device-tree bindings"?
> >>
> >> It breaks existing users of DTS and kernel.
> > 
> > I assume you mean it breaks if someone is using old approach DTS with a
> > kernel that would have ICE driver merged. Yes, that it does. And for
> > that, in the v3, I'll make of_qcom_ice_get check if there is a reg entry
> > with name "ice" and create an ICE instance but for the same dev as the
> > consumer driver. OTOH, if there is no reg entry called "ice", it will
> > look up a device based on phande of qcom,ice property. This will allow
> > legacy style DTS to work fine, while using the unified driver as a
> > library, in that case. For newer platforms, the recommended approach
> > will be to add a new ICE node and use qcom,ice property.
> 
> For the driver this sounds good. I still think that existing (older) DTS
> should not have regs removed, because this affects other users of kernel
> DTS.

Yes, that's what I meant, the already supported platforms will remain
with ice reg in the consumer node.

> 
> 
> Best regards,
> Krzysztof
>