Re: Commit 8ae030c34 breaks USB on the Raspberry Pi 4

From: nicolas saenz julienne <nsaenz@kernel.org>
To: Michael Stapelberg <michael+lkml@stapelberg.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
	 linux-arm-kernel@lists.infradead.org,
	Vinod Koul <vkoul@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Stefan Wahren <stefan.wahren@i2se.com>
Subject: Re: Commit 8ae030c34 breaks USB on the Raspberry Pi 4
Date: Wed, 15 Sep 2021 10:54:41 +0200	[thread overview]
Message-ID: <4a8bea181bd287f8fa394d19f9a68fcd9a955e15.camel@kernel.org> (raw)
In-Reply-To: <CANnVG6mWDubBM6FhzkxxYx3Ff9t6qj1_D-qpoPZTbHYsOwoHow@mail.gmail.com>

On Wed, 2021-09-15 at 09:55 +0200, Michael Stapelberg wrote:
> Hey Nicolas
> 
> On Wed, 15 Sept 2021 at 09:42, nicolas saenz julienne <nsaenz@kernel.org> wrote:
> > 
> > Hi Michael,
> > 
> > On Wed, 2021-09-15 at 08:33 +0200, Michael Stapelberg wrote:
> > > Thanks for your mail.
> > > 
> > > My system does not use any Linux kernel modules (=m), all required
> > > code is compiled into the kernel itself (=y).
> > > The root file system does not contain any .ko files.
> > 
> > Are you building your own kernels? Then I suggest to configure the
> > raspberrypi-reset driver as builtin (=y) so it's available in your kernel
> > image.
> 
> Yes, I have already done that. I was more interested in fixing this
> problem for others, and/or avoiding similar problems in the future.
> 
> > 
> > Could you provide more information on how your system/rootfs is built and
> > setup?
> 
> Please see https://gokrazy.org/, specifically https://gokrazy.org/quickstart/.
> The source for the gokr-packer tool is at
> https://github.com/gokrazy/tools/tree/master/cmd/gokr-packer
> 
> In summary, my tool builds a read-only SquashFS root file system that
> directly starts processes written in Go.
> The boot partition (FAT32 for the Raspberry Pi) contains only the
> Linux kernel and Raspberry Pi firmware files.

Thanks for the info.

IMO the solution is to maintain your own configuration. The decision not to use
kernel modules, even if reasonable given the scope of gokrazy, is a big
deviation from how the kernel is regularly consumed. The majority of the arm64
defconfig users need the kernel image to be as small as possible to avoid
bloating the boot partition, and allowing for reasonable boot speeds (imagine
having to load a 1GB kernel image from the SD card).

Regards,
Nicolas

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