linux-kernel - RE: [PATCH 03/10] PCI: AMD SATA IDE mode quirk

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Date:	Fri, 22 Feb 2008 13:49:20 +0800
From:	"Cai, Crane" <Crane.Cai@....com>
To:	"Matthew Wilcox" <matthew@....cx>,
	"Greg Kroah-Hartman" <gregkh@...e.de>
Cc:	<linux-pci@...ey.karlin.mff.cuni.cz>,
	<linux-kernel@...r.kernel.org>,
	"Linus Torvalds" <torvalds@...l.org>,
	"Andrew Morton" <akpm@...l.org>
Subject: RE: [PATCH 03/10] PCI: AMD SATA IDE mode quirk

> On Thu, Feb 21, 2008 at 03:47:33PM -0800, Greg Kroah-Hartman wrote:
> > +static void __devinit quirk_amd_ide_mode(struct pci_dev *pdev)
> >  {
> > -	/* set sb600 sata to ahci mode */
> > -	if ((pdev->class >> 8) == PCI_CLASS_STORAGE_IDE) {
> > -		u8 tmp;
> > +	/* set sb600/sb700/sb800 sata to ahci mode */
> > +	u8 tmp;
> >  
> > +	pci_read_config_byte(pdev, PCI_CLASS_DEVICE, &tmp);
> > +	if (tmp == 0x01) {
> >  		pci_read_config_byte(pdev, 0x40, &tmp);
> 
> This seems like a dis-improvement.  Why are we reading a 
> config byte for something we already have in the pci_dev?  
> Why are we now checking against 0x01 instead of a symbolic 
> constant?  Why are we no longer checking that this is 
> PCI_BASE_CLASS_STORAGE?
It is a quirk. In pci_ids.h did have PCI_CLASS_STORAGE_IDE 
and PCI_BASE_CLASS_STORAGE, these can not represent 
the right situation we want to check. 0x01 represents 
PCI_CLASS_STORAGE_IDE last 2 bit. Also because it 
is a quirk, I do not think we need to change pci_ids.h. So 0x01 
used. 
> > -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, 
> > PCI_DEVICE_ID_ATI_IXP600_SATA, quirk_sb600_sata); 
> > -DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, 
> > PCI_DEVICE_ID_ATI_IXP700_SATA, quirk_sb600_sata);
> > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, 
> > +PCI_DEVICE_ID_ATI_IXP600_SATA, quirk_amd_ide_mode); 
> > +DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_ATI, 
> > +PCI_DEVICE_ID_ATI_IXP600_SATA, quirk_amd_ide_mode); 
> > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, 
> > +PCI_DEVICE_ID_ATI_IXP700_SATA, quirk_amd_ide_mode); 
> > +DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_ATI, 
> > +PCI_DEVICE_ID_ATI_IXP700_SATA, quirk_amd_ide_mode);
> 
> Nothing in the changelog entry suggests why we now need 
> FIXUP_RESUME entries when we didn't before.
> 
PCI configuration space will be changed by BIOS and then in pci
init and restore. So resume also needed.
> --
> Intel are signing my paycheques ... these opinions are still 
> mine "Bill, look, we understand that you're interested in 
> selling us this operating system, but compare it to ours.  We 
> can't possibly take such a retrograde step."
> 
> 

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