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Date:   Sun, 04 Sep 2022 23:47:32 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Marc Zyngier" <maz@kernel.org>,
        "Russell King" <linux@armlinux.org.uk>
Cc:     "Arnd Bergmann" <arnd@kernel.org>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        "Christoph Hellwig" <hch@lst.de>,
        "Linus Walleij" <linus.walleij@linaro.org>
Subject: Re: [PATCH 0/4] ARM: footbridge: cleanups
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On Sun, Sep 4, 2022, at 6:10 PM, Marc Zyngier wrote:
> On Sun, 04 Sep 2022 13:09:42 +0100,
> "Russell King (Oracle)" <linux@armlinux.org.uk> wrote:
>> > > Cc: Russell King <linux@armlinux.org.uk>
>> > > Cc: Christoph Hellwig <hch@lst.de>
>> > > Cc: Linus Walleij <linus.walleij@linaro.org>
>> > > Cc: Marc Zyngier <maz@kernel.org>
>> > 
>> > I finally managed to give this a go on my netwinder using v2 of patch
>> > 5/4 (!), and the box booted nicely.

Excellent, thanks for testing!

>> > Note that apart from the serial console, everything I'm using on this
>> > box is PCI (I tried to enable sound and failed, probably because I
>> > can't select CONFIG_ISA anymore on this machine).

There are a couple of ISA-style devices on the superIO chip,
and I had checked this one to see what actually uses the
ISA DMA. As far as I can tell, the ECP parallel port and floppy
should still fully work in DMA mode, but these don't depend on
CONFIG_ISA. Irda and waveartist are gone, and the keyboard/mouse,
RTC, uart etc are neither DMA capable not based on CONFIG_ISA.

>> That tends to mean, therefore, that the statement "CONFIG_ISA is for
>> add-in cards" is wrong, because it's caused a user-visible regression
>> by killing sound support on Netwinders!
>
> To some extent, yes. Adding this allows me to peek at some of the ISA
> soundcards:
>
> diff --git a/arch/arm/mach-footbridge/Kconfig b/arch/arm/mach-footbridge/Kconfig
> index f452663576d1..f4c4222fa7c0 100644
> --- a/arch/arm/mach-footbridge/Kconfig
> +++ b/arch/arm/mach-footbridge/Kconfig
> @@ -31,6 +31,7 @@ config ARCH_NETWINDER
>  	select CLKEVT_I8253
>  	select CLKSRC_I8253
>  	select FORCE_PCI
> +	select ISA
>  	help
>  	  Say Y here if you intend to run this kernel on the Rebel.COM
>  	  NetWinder.  Information about this machine can be found at:
>
> However, the Waveartist driver has gone the way of the dodo (together
> with the rest of the OSS support in 4.15), and it isn't obvious to me
> whether one of the several SoundBlaster drivers is appropriate on this
> machine.
>
> I also cannot say I deeply care, to be honest.

I already made sure that there are no devices in the defconfig
that get disabled when turning off CONFIG_ISA, so at least for
anyone using the defconfig, my change made no difference.

It's possible that the sb16 ISA driver works in non-PNP mode,
but it appears to look for the wrong IRQ number and mixer,
the other SB16 compatible drivers all assume ISAPNP or PCI.

My guess is that to use this properly, one would have
to turn take the mixer bits from the OSS waveartist
driver and turn that into an ALSA driver along with a
simple platform driver frontend for sb16-common.ko.

      Arnd