linux-kernel - Re: [PATCH v4] powerpc: Use shared font data

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Message-ID: <aQp3Ve1C-aZ8BhXa@gallifrey>
Date: Tue, 4 Nov 2025 21:59:49 +0000
From: "Dr. David Alan Gilbert" <linux@...blig.org>
To: Stan Johnson <userm57@...oo.com>
Cc: mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
	sam@...nborg.org, benh@...nel.crashing.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	rdunlap@...radead.org, Cedar Maxwell <cedarmaxwell@....com>,
	Finn Thain <fthain@...ux-m68k.org>
Subject: Re: [PATCH v4] powerpc: Use shared font data

* Stan Johnson (userm57@...oo.com) wrote:
> Please see the attached config file that Finn sent to me along with his
> patch. The relevant line is "CONFIG_BOOTX_TEXT=y"; without that, the kernel
> boots on the Wallstreet.

Thanks - I'll have a play.

Dave

> On 11/4/25 10:59 AM, Dr. David Alan Gilbert wrote:
> > * Finn Thain (fthain@...ux-m68k.org) wrote:
> > > 
> > > On Mon, 3 Nov 2025, Dr. David Alan Gilbert wrote:
> > > 
> > > > 
> > > > > Anyway, I imagine that the problem with your patch was that it relies
> > > > > on font data from a different (read only) section, which is
> > > > > unavailable for some reason (MMU not fully configured yet?)
> > > > > 
> > > > > So I've asked Stan to test a patch that simply removes the relevant
> > > > > 'const' keywords. It's not a solution, but might narrow-down the
> > > > > search.
> > > > 
> > > 
> > > Stan tested my patch to remove 'const' from the font_desc and font_data
> > > structs but it did not help. (There goes that theory.)
> > > 
> > > > I wonder if this is a compiler-flag-ism;  I see
> > > > arch/powerpc/kernel/Makefile has a pile of special flags, and for
> > > > btext.o it has a -fPIC (as well as turning off some other flags). I
> > > > wonder if bodging those in lib/fonts/Makefile for
> > > > lib/fonts/font_sun8x16.c fixes it? But... this is data - there's no code
> > > > is there - are any of those flags relevant for data only?
> > > > 
> > > 
> > > I don't know. But I'm sure Stan would be willing to test a patch for you.
> > 
> > Can one of you point me at the config you're testing with so I can
> > try some builds with it.
> > 
> > Dave
> > 
> > > > > 
> > > > > The BootX bootloader doesn't work on New World systems, which is
> > > > > probably why we don't see this regression on anything newer than a
> > > > > Wallstreet.
> > > > > 
> > > > > It's likely that other Old World systems are also affected, if they
> > > > > are using BootX. We don't yet know whether the regression also affects
> > > > > Old World systems using the iQUIK bootloader instead of BootX.
> > > > 
> > > > OK, remember I don't think I've ever tried PPC via MacOS booting, so not
> > > > familiar with it.
> > > > 
> > > 
> > > I will try to set up a MacOS guest in QEMU, to see if the hang can be
> > > reproduced that way.
> > > 


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