Re: [PATCH 12/12] arm64: dts: exynos: Add Exynos850 SoC support

[Sam Protsenko <semen.protsenko@xxxxxxxxxx>]

On Fri, 6 Aug 2021 at 15:48, Krzysztof Kozlowski
<krzysztof.kozlowski@xxxxxxxxxxxxx> wrote:
>
> On 06/08/2021 14:32, Krzysztof Kozlowski wrote:
> > On 06/08/2021 14:07, Sam Protsenko wrote:
> >> On Fri, 6 Aug 2021 at 10:49, Krzysztof Kozlowski
> >> <krzysztof.kozlowski@xxxxxxxxxxxxx> wrote:
> >>>
> >>> On 06/08/2021 01:06, Sam Protsenko wrote:
> >>>> On Sat, 31 Jul 2021 at 12:03, Krzysztof Kozlowski
> >>>> <krzysztof.kozlowski@xxxxxxxxxxxxx> wrote:
> >>>>
> >>>>>>
> >>>>>> This patch adds minimal SoC support. Particular board device tree files
> >>>>>> can include exynos850.dtsi file to get SoC related nodes, and then
> >>>>>> reference those nodes further as needed.
> >>>>>>
> >>>>>> Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> >>>>>> ---
> >>>>>>  .../boot/dts/exynos/exynos850-pinctrl.dtsi    | 782 ++++++++++++++++++
> >>>>>>  arch/arm64/boot/dts/exynos/exynos850-usi.dtsi |  30 +
> >>>>>>  arch/arm64/boot/dts/exynos/exynos850.dtsi     | 245 ++++++
> >>>>>
> >>>>> Not buildable. Missing Makefile, missing DTS. Please submit with initial
> >>>>> DTS, otherwise no one is able to verify it even compiles.
> >>>>>
> >>>>
> >>>> This device is not available for purchase yet. I'll send the patch for
> >>>> board dts once it's announced. I can do all the testing for now, if
> >>>> you have any specific requests. Would it be possible for us to review
> >>>> and apply only SoC support for now? Will send v2 soon...
> >>>
> >>> What you propose is equal to adding a driver (C source code) without
> >>> ability to compile it. What's the point of having it in the kernel? It's
> >>> unverifiable, unbuildable and unusable.
> >>>
> >>
> >> Yes, I understand. That's adding code with no users, and it's not a
> >> good practice.
> >>
> >>> We can review the DTSI however merging has to be with a DTS. Usually the
> >>> SoC vendor adds first an evalkit (e.g. SMDK board). Maybe you have one
> >>> for Exynos850? Otherwise if you cannot disclose the actual board, the
> >>> DTSI will have to wait. You can submit drivers, though.
> >>>
> >>
> >> Sure, let's go this way. I'll send v2 soon. Improving patches and
> >> having Reviewed-by tag for those would good enough for me at this
> >> point. I'll continue to prepare another Exynos850 related patches
> >> until the actual board is announced, like proper clock driver, reset,
> >> MMC, etc. Is it ok if I send those for a review too (so I can fix all
> >> issues ahead)?
> >
> > Sure, prepare all necessary drivers earlier. I suspect clocks will be a
> > real pain because of significant changes modeled in vendor kernel. I
> > remember Paweł Chmiel (+Cc) was doing something for these:
> > https://github.com/PabloPL/linux/tree/exynos7420
> >
> > I mentioned before - you should also modify the chipid driver. Check
> > also other drivers in drivers/soc/samsung, although some are needed only
> > for suspend&resume.
> >

Yes, in due course... There won't be much problems with chip-id
driver. But pretty much all platform drivers depend on clk, and that
one I'm afraid I'll have to implement from scratch. Will take me a
while, as vendor's codebase for clk driver is huge and depend on
another huge non-upstreamable abstraction layer framework they have,
and also they have kind of strange home brewed composite clocks...
Anyway, that's what I'm going to look into next.

Btw, I just sent v2 :)

>
> You can also take a look at Exynos8895 efforts:
> https://github.com/ivoszbg/linux/commits/for-upstream/exynos8895
>
> Since knowledge, datasheets and efforts are quite spread all over, I
> keep track of some work here:
> https://exynos.wiki.kernel.org/community
>

Thanks, Krzysztof! I'm sure that info will help a lot with further
work, like clock driver.

>
> Best regards,
> Krzysztof