linux-kernel - Re: [PATCH] arm64: defconfig: Enable Qualcomm interconnects as built-in

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Message-ID: <CACr-zFAMa3Awx16avbXNMRhkELFkEZedZfHVCFuFc4fitWFL4w@mail.gmail.com>
Date: Wed, 12 Mar 2025 16:28:49 +0100
From: Christopher Obbard <christopher.obbard@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Dmitry Baryshkov <lumag@...nel.org>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@....qualcomm.com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] arm64: defconfig: Enable Qualcomm interconnects as built-in

Hi Krzysztof,

On Wed, 12 Mar 2025 at 12:34, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 12/03/2025 12:10, Christopher Obbard wrote:
> > Hi Krzysztof,
> >
> > On Wed, 12 Mar 2025 at 09:56, Krzysztof Kozlowski <krzk@...nel.org> wrote:
> >>
> >> On 11/03/2025 20:15, Christopher Obbard wrote:
> >>> Hi Dmitry,
> >>>
> >>> On Tue, 11 Mar 2025 at 19:58, Dmitry Baryshkov <lumag@...nel.org> wrote:
> >>>>
> >>>> On Tue, Mar 11, 2025 at 07:10:06PM +0100, Christopher Obbard wrote:
> >>>>> I sent this patch to start the discussion, some things I found:
> >>>>>
> >>>>> 1) Some interconnects are missing from arm defconfig. Should they be =y too ?
> >>>>
> >>>> No, unless those are required for the UART console.
> >>>
> >>> OK, that makes sense. FWIW the cryptic (to me, at least) commit log on
> >>> https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6eee808134ecf1c1093ff1ddfc056dc5e469d0c3
> >>> made me think that the interconnects should be built-in on all devices.
> >>>
> >>> Of course, the real problem here is RB3gen2 not actually finding the
> >>> UFS/eMMC device due to no interconnect driver.
> >>> Until now, I have been building that into the kernel. I will
> >>> investigate instead shoving into the initrd (in both debian and
> >>> fedora) which should solve my issue and render this patchset useless.
> >>
> >> For Qualcomm platforms you are expected to always have initramfs, thus
> >> you will have the modules for UFS/eMMC mounts. I don't understand the
> >> problem which you were trying to solve.
> >>
> >> The interconnects were built in *only* because of need for serial
> >> console. Only.
> >
> > Thanks for confirming. It is all clear now.
> >
> > Consider this patch dropped from my side.
> >
> > For reference, I am working on updating initramfs generation tools in
> > Debian/Fedora to include the required interconnect modules. Currently
> > the interconnect drivers are built as modules in these distros, but
> > are not included in the initrd. That is where my confusion initially
> > stemmed from.
>
> Sure. This defconfig is anyway for us - developers, not for the distros
> to use directly. Distros have much bigger configs and use almost
> everything as module.

Completely agree - my usual workflow is to build with the kernel's
defconfig (disto config is generally huge) and install the resulting
kernel into my Debian image.

Installing a kernel built with `make bindeb-pkg` then calls
update-initramfs to create the initrd - which then should pack the
RIGHT modules needed for loading storage/network boot/etc into the
initrd. In this case it simply didn't yet copy that module into the
initrd in Debian, so I will sort it out in the distro space ;-).

We can likely stop this discussion now as it's clear to everyone
what's going on I think.

Thanks,

Chris