linux-kernel - Re: [PATCH v3 1/1] arm64: dts: qcom: Add Lenovo Yoga C630

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Date:   Wed, 4 Sep 2019 18:07:01 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     agross@...nel.org, robh+dt@...nel.org, mark.rutland@....com,
        bjorn.andersson@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/1] arm64: dts: qcom: Add Lenovo Yoga C630

On Wed, 04 Sep 2019, Sudeep Holla wrote:

> On Wed, Sep 04, 2019 at 05:12:47PM +0100, Lee Jones wrote:
> > On Wed, 04 Sep 2019, Sudeep Holla wrote:
> >
> > > On Wed, Sep 04, 2019 at 01:16:06PM +0100, Lee Jones wrote:
> > > > From: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > >
> > > > The Lenovo Yoga C630 is built on the SDM850 from Qualcomm, but this seem
> > > > to be similar enough to the SDM845 that we can reuse the sdm845.dtsi.
> > > >
> > > > Supported by this patch is: keyboard, battery monitoring, UFS storage,
> > > > USB host and Bluetooth.
> > > >
> > >
> > > Just curious to know if the idea of booting using ACPI is completely
> > > dropped as it's extremely difficult(because the firmware is so hacked
> > > up and may violate spec, just my opinion) for whatever reasons.
> >
> > Once [0] is applied, we can boot Mainline using ACPI.
> >
> 
> Good to know.
> 
> > > We just made ACPI table version checking more lenient for this platform
> > > and would be good to know if we continue to run ACPI on that or will
> > > abandon and just use DT.
> >
> > Which patch are you referring to?  If you mean the ACPI v5.0 vs v5.1
> > patch authored by Ard, then yes I know, I instigated it's existence
> > due to these devices.
> >
> 
> Yes exactly that one.
> 
> > DT will *always* be more enabled than ACPI, so it's advised that you
> > use DT for anything useful.  ACPI booting is ideal for things like
> > installing distros however, since they do not tend to provide DTBs in
> > their installers.
> 
> OK, as along as it gets tested/used in some form, that's fine. I do agree
> that DT will be more useful on that platform as it was derived from mobile
> based SoC SDM845 rather than solely designed for Laptops and with more
> alignment with ACPI spec. The way whole power/clock management is done
> with ACPI on this pulls me towards DT ;)

Exactly.  For Power Management on ACPI, we need to re-implement the
"Windows-compatible System Power Management Controller" (PEP), which
considering there isn't any documentation and/or source, would be a
mammoth challenge, if at all possible.

Feel free to provide your {Ack,Review)ed-by for this patch. :)

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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