linux-kernel - Re: [PATCH 18/18] arm64: apple: Add initial Mac Mini 2020 (M1) devicetree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3d61ca6d-98a1-b78a-07da-cd20834de5a1@marcan.st>
Date:   Wed, 10 Feb 2021 21:56:08 +0900
From:   Hector Martin <marcan@...can.st>
To:     Daniel Palmer <daniel@...f.com>
Cc:     Tony Lindgren <tony@...mide.com>, Arnd Bergmann <arnd@...nel.org>,
        DTML <devicetree@...r.kernel.org>, Marc Zyngier <maz@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        SoC Team <soc@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Olof Johansson <olof@...om.net>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 18/18] arm64: apple: Add initial Mac Mini 2020 (M1)
 devicetree

On 10/02/2021 21.24, Daniel Palmer wrote:
> This exact problem exists for MStar/SigmaStar too.
> As it stands there is no documentation to show what the actual clock
> tree looks like so everything is guess and I need to come up with numbers.
> I'm interested to see what the solution to this is as it will come up again
> when mainlining chips without documentation.

So far the answer seems to be to take the best guess available, and then 
we get to fix it until we have real users and breaking DT compatibility 
is no longer an option... :-)

>> The purpose of the clock in this particular case is just to make the
>> uart driver work, since it wants to know its reference clock; there is
>> work to be done here to figure out the real clock tree
> 
> FWIW arm/boot/dts/mstar-v7.dtsi has the same issue: Needs uart,
> has no uart clock. In that instance the uart clock setup by u-boot
> is passed to the uart driver as a property instead of creating a fake
> clock.

In our case it's an existing driver (with patches) that is already 
integrated with the clock infrastructure, so it makes sense to use a 
fixed-clock instead of just an ad-hoc property.

-- 
Hector Martin (marcan@...can.st)
Public Key: https://mrcn.st/pub