linux-kernel - Re: [PATCH] PCI: Always set prefetchable base/limit upper32 registers

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Date:	Mon, 30 Nov 2009 14:43:01 -0700
From:	Alex Williamson <alex.williamson@...com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: Always set prefetchable base/limit upper32
 registers

On Mon, 2009-11-30 at 13:36 -0800, Yinghai Lu wrote:
> Alex Williamson wrote:
> > Prior to 1f82de10 we always initialized the upper 32bits of the
> > prefetchable memory window, regardless of the address range used.
> > Now we only touch it for a >32bit address, which means the upper32
> > registers remain whatever the BIOS initialized them too.
> > 
> > It's valid for the BIOS to set the upper32 base/limit to
> > 0xffffffff/0x00000000, which makes us program prefetchable ranges
> > like 0xffffffffabc00000 - 0x00000000abc00000
> > 
> > Revert the chunk of 1f82de10 that made this conditional so we always
> > write the upper32 registers.
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@...com>
> > ---
> > 
> >  drivers/pci/setup-bus.c |    8 +++-----
> >  1 files changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index cb1a027..127d759 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -221,11 +221,9 @@ static void pci_setup_bridge(struct pci_bus *bus)
> >  	}
> >  	pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, l);
> >  
> > -	if (pref_mem64) {
> > -		/* Set the upper 32 bits of PREF base & limit. */
> > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, bu);
> > -		pci_write_config_dword(bridge, PCI_PREF_LIMIT_UPPER32, lu);
> > -	}
> > +	/* Set the upper 32 bits of PREF base & limit. */
> > +	pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, bu);
> > +	pci_write_config_dword(bridge, PCI_PREF_LIMIT_UPPER32, lu);
> >  
> >  	pci_write_config_word(bridge, PCI_BRIDGE_CONTROL, bus->bridge_ctl);
> >  }
> 
> when pref_mem64=0 it means that pref register is only 32 bit, we should not touch upper 32bits.

Did you read my patch description?  In that case bu = lu = 0 and we
clear whatever state the BIOS left for those registers.

Alex

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