linux-kernel - Re: Current git very broken on the Dreamcast

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Date:	Mon, 18 Feb 2008 17:57:05 +0900
From:	"Magnus Damm" <magnus.damm@...il.com>
To:	"Adrian McMenamin" <adrian@...golddream.dyndns.info>
Cc:	linux-sh@...r.kernel.org,
	"Paul Mundt" <lethal@...rs.sourceforge.net>, matsu@...l.co.jp,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Current git very broken on the Dreamcast

Hi Adrian,

[fixed up Matsubara-sans address]

On Feb 17, 2008 4:48 AM, Adrian McMenamin
<adrian@...golddream.dyndns.info> wrote:
> On Sat, 2008-02-16 at 18:38 +0000, Adrian McMenamin wrote:
> > Will seek to bisect this, but I have just updated my sources to the
> > latest git and it is not booting at all on the Dreamcast.
> >
> > With early printk on, I get nothing more than this before an instant
> > reboot:
> >
> > [    0.000000] Linux version 2.6.25-rc2-10953-g52065cd
> > (adrian@...sclass) (gcc version 3.4.6) #511 PREEMPT Sat Feb 16 18:31:43
> > GMT 2008
> > [    0.000000] console [sercon0] enabled
> > [    0.000000] Booting machvec: Sega Dreamcast
>
>
> adrian@...sclass:~/gdrom-dev$ git bisect good
> e036eaa681a17f71b64f6d9040fe605555623919 is first bad commit
> commit e036eaa681a17f71b64f6d9040fe605555623919
> Author: Magnus Damm <magnus.damm@...il.com>
> Date:   Thu Feb 14 13:52:43 2008 +0900
>
>     sh: use ctrl_in/out for on chip pci access
>
>     This patch makes sure ctrl_inN/outN are used instead of inN/outN for
> on chip
>     pci registers. Without this patch addresses may be adjusted using
> the value
>     in generic_io_base. This patch makes it possible to set
> generic_io_base and
>     have pci without reading and writing all over the place.
>
>     Signed-off-by: Magnus Damm <damm@...l.co.jp>
>     Acked-by: Katsuya MATSUBARA <matsu@...l.co.jp>
>     Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
>
> :040000 040000 17a9f8181301e3a082d8a1a2fdef9b13ff1185e4
> 87e4a2e912be56b0d12e8a92db9489d6615c31f7 M      arch

Thanks for tracking this down and sorry for breaking the dreamcast pci driver.

Most code for the dreamcast currently do direct register access using
ctrl_inN/outN or readN/writeN. Only a few places use inN/outN and
depend on the value of generic_io_base. Doing inN/outN is ok (but
outdated, use ioreadN/iowriteN instead) in a portable pci/isa driver,
but it doesn't make sense for any dreamcast specific code to rely on
generic_io_base. For the dreamcast we already know the address at
compile time so doing adjustment during runtime is just unnecessary
overhead.

It is of course possible to revert the dreamcast-specific bits of the
commit you pointed out, but I think the change for the dreamcast makes
sense since it makes the code both faster and more uniform.

However, at this point it is broken. Sorry about that. I just looked
through all upstream dreamcast-specific code I could find and irq.c is
now the only file that does inN/outN. I've attached a patch that makes
the irq code independent of generic_io_base. There is also another
patch attached that adjusts the addresses of the pci register.
Together they should solve the problem you are seeing. Please try them
on top of 2.6.25-rc2.

With these patches io ports count from 0 -> 8k-1 instead of being a
pointer. We currently rely on generic_io_base logic but that will be
changed in the future.

Please let me know the results. Thank you.

/ magnus

Download attachment "linux-2.6.25-rc2-sh-dreamcast-irq-20080218.patch" of type "application/octet-stream" (2260 bytes)

Download attachment "linux-2.6.25-rc2-sh-dreamcast-pci-20080218b.patch" of type "application/octet-stream" (1668 bytes)