linux-kernel - Re: [PATCH] x86-64: disable the GART in shutdown

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Date:	Sun, 24 Jun 2007 17:22:30 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	ak@...e.de, alan@...rguk.ukuu.org.uk, ebiederm@...ssion.com,
	muli@...ibm.com, vgoyal@...ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86-64: disable the GART in shutdown

On 6/23/07, Andrew Morton <akpm@...ux-foundation.org> wrote:
> >  void __init gart_iommu_init(void)
> >  {
> >       struct agp_kern_info info;
> > diff --git a/arch/x86_64/kernel/pci-dma.c b/arch/x86_64/kernel/pci-dma.c
> > index 9f80aad..64f2ab3 100644
> > --- a/arch/x86_64/kernel/pci-dma.c
> > +++ b/arch/x86_64/kernel/pci-dma.c
> > @@ -322,6 +322,13 @@ static int __init pci_iommu_init(void)
> >       return 0;
> >  }
> >
> > +void pci_iommu_shutdown(void)
> > +{
> > +#ifdef CONFIG_IOMMU
> > +     gart_iommu_shutdown();
> > +#endif
> > +}
>
> It'd be better to avoid the ifdef-in-C by providing a stub function in a
> header file if !CONFIG_IOMMU.  That's quite standard kernel practice and
> might help avoid some other problems...

move ifdef into gart_iommu_shudown()?

>
> >  #ifdef CONFIG_PCI
> >  /* Many VIA bridges seem to corrupt data for DAC. Disable it here */
> >
> > diff --git a/arch/x86_64/kernel/reboot.c b/arch/x86_64/kernel/reboot.c
> > index 7503068..e6e65c2 100644
> > --- a/arch/x86_64/kernel/reboot.c
> > +++ b/arch/x86_64/kernel/reboot.c
> > @@ -16,6 +16,7 @@
> >  #include <asm/pgtable.h>
> >  #include <asm/tlbflush.h>
> >  #include <asm/apic.h>
> > +#include <asm/proto.h>
> >
> >  /*
> >   * Power off function, if any
> > @@ -81,6 +82,7 @@ static inline void kb_wait(void)
> >  void machine_shutdown(void)
> >  {
> >       unsigned long flags;
> > +
> >       /* Stop the cpus and apics */
> >  #ifdef CONFIG_SMP
> >       int reboot_cpu_id;
> > @@ -111,6 +113,8 @@ void machine_shutdown(void)
> >       disable_IO_APIC();
> >
> >       local_irq_restore(flags);
> > +
> > +     pci_iommu_shutdown();
> >  }
>
> And does the kernel work OK if CONFIG_PCI=n?  I think so from inspection,
> by luck.

x86_64 always have that PCI enabled?

>
> >  void machine_emergency_restart(void)
> > diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
> > index 85255db..fb9f73e 100644
> > --- a/include/asm-x86_64/proto.h
> > +++ b/include/asm-x86_64/proto.h
> > @@ -85,11 +85,13 @@ extern int exception_trace;
> >  extern unsigned cpu_khz;
> >  extern unsigned tsc_khz;
> >
> > +extern void pci_iommu_shutdown(void);
>
> This is the only pci-related function which is declared in proto.h.  I
> suspect you chose the wrong header file for this declaration.
i tried to put that into dma_mapping.h, but htat will need more header
files before that to make the compiler happy, may need to find another
header file for it.

YH
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