Re: [PATCH v1 0/6] x86/boot: Enable earlyprintk on MMIO (8-bit)

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Fri, May 02, 2025 at 10:33:49AM -0700, David Woodhouse wrote:
> On Fri, 2025-05-02 at 15:29 +0300, Andy Shevchenko wrote:
> > Some of the platforms may have no legacy COM ports and only provide
> > an MMIO accessible UART. Add support for such to earlyprintk for the
> > boot phase of the kernel.
> 
> Shiny. I had to hack QEMU's PCI serial port to do unnatural things, in
> order to test the mmio32 variant which was the only thing the
> earlyprintk code used to support. But I *did* so, and it works with the
> kexec debugging.
> 
> Can you add support for this mode to the kexec debugging too, please?

Do you mean to add MMIO 8-bit to kexec assembly code and other parts like you
did in the below mentioned change?

I can try it at some point, but have no time right now for this.
I would appreciate if you can give a try for this patch series
functionality to see if it helps for the initial messages (as
far as I understand you also want to have this in the second
kernel, right?).

> I believe it's currently in tip/asm. This should be a simple example to
> work from:
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=x86/asm&id=7516e7216bdfb9e2fab0a0ca3bd23cb2e61e46ed



-- 
With Best Regards,
Andy Shevchenko