linux-kernel - Re: [PATCH v2 12/15] arm64: dts: rockchip: Enable dmc and dfi nodes on gru

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Date:   Fri, 4 Mar 2022 12:47:25 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Peter Geis <pgwipeout@...il.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Lin Huang <hl@...k-chips.com>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        Derek Basehore <dbasehore@...omium.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-pm <linux-pm@...r.kernel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Gaël PORTAY <gael.portay@...labora.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v2 12/15] arm64: dts: rockchip: Enable dmc and dfi nodes
 on gru

Hi Peter,

On Fri, Mar 4, 2022 at 6:47 AM Peter Geis <pgwipeout@...il.com> wrote:
> I'm trying to bring this series over to rockpro64 (and eventually the
> pinephone-pro) and am running into some snags.

Dumb question: is DDR DVFS supported on these systems in the
"production" (vendor kernel? I'm not really familiar with these
devices) software? I partly ask, because while I didn't do some of
this first-hand, I'm aware that it was a real ordeal to get things
stabilized (e.g., getting all the timings right; communicating the
right details from bootloader to ATF; etc.), so if no one did these
things in the first place, it's probably difficult to get working now
just by guessing.

But if it works on a customized kernel, then that's a different story.

> Essentially, anytime a transition happens, the board locks up.
> I've disabled the extra power save disable flags and adjusted the OPPs
> for rockpro64's power.
> Transitions anywhere from the default 800mhz cause a lock.
>
> I'm digging deeper, but I'm hoping you can answer some questions in
> the meantime:
> 1. Does this require something from firmware that isn't available on
> Mainline ATF? (AKA special firmware to the Chromebook line)

I don't know precisely. Chromebooks track mainline ATF, but somewhere
before initial product launch, each platform gets its own firmware
branch. On that firmware branch, we still try to stay in sync with
mainline to some extent (e.g., submit to mainline and cherry-pick to
branch), but it's not guaranteed.

Anyway, you can inspect our code here:
https://chromium.googlesource.com/chromiumos/third_party/arm-trusted-firmware/+log/refs/heads/firmware-gru-8785.B
https://chromium.googlesource.com/chromiumos/third_party/coreboot/+log/refs/heads/firmware-gru-8785.B

Brian