The libata driver will not work with an M5229 set into native IDE
mode (the old drivers/pci one does) if the M5229 does not provide
it's own IRQ.

The M5229 implementation embedded into the ALI M1543 uses the
M1543's ISA PIC to provide the interrupts and thus does not have
an valid PCI IRQ set. This quirk detects the abscence of IRQ and
sets the M5229 back into compatibility mode to use IRQs 14 and 15
so that libata works correctly.

Note, I belive that the check for an valid interrupt line is
correct, I only have an M5229 in an ALI M1543 to check this
on. It would be useful to confirm that a M5229 with an valid IRQ
does not trigger this quirk.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>

Index: linux-2.6.27-rc6-cats1/drivers/pci/quirks.c
===================================================================
--- linux-2.6.27-rc6-cats1.orig/drivers/pci/quirks.c	2008-09-11 11:26:35.000000000 +0100
+++ linux-2.6.27-rc6-cats1/drivers/pci/quirks.c	2008-09-12 12:18:05.000000000 +0100
@@ -905,6 +905,34 @@ static void __devinit quirk_svwks_csb5id
 }
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_CSB5IDE, quirk_svwks_csb5ide);
 
+/* Some systems set the ALI M5229 in the ALI M1543 bridge to native mode,
+ * which cannot be supported by the pata_ali.c driver (the old drivers/ide
+ * makes a compatibility effort to change the IDE interrupts).
+ */
+static void __devinit quirk_ali_ide_compatibility(struct pci_dev *pdev)
+{
+	u8 tmp;
+
+	/* pdev->irq and pdev->pin have yet to be initialised, so check
+	 * by reading from the configuration header to see if we've got
+	 * a valid interrupt line. */
+
+	pci_read_config_byte(pdev, PCI_INTERRUPT_LINE, &tmp);
+	if (tmp != 0xff)
+		return;
+
+	pci_read_config_byte(pdev, PCI_CLASS_PROG, &tmp);
+	if (tmp & 0x5) {
+		dev_info(&pdev->dev, "quirk: changing to IDE compatibility mode\n");
+
+		tmp &= ~0x05;
+		pdev->class &= ~0x05;
+		pci_write_config_byte(pdev, PCI_CLASS_PROG, ...
[ message continues ]

Why does this need to be a quirk rather than something in the libata ALi

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"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."
--

[ message continues ]

The short answer is that "Alan Cox says not in libata", the longer
one can be found:


-- 
-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.

--

[ message continues ]

Thanks for the reference.  I've now read that thread.  I'm not entirely
convinced Alan is right; I think it's preferable to confine this
quirking to the driver and fix up the BARs in the driver as well.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"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."
--

[ message continues ]

I'm not convinced by that, I've no idea how that will affect the system

-- 
-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.

--

[ message continues ]

This is a bit surprising, considering that libata works for all IDE mode 
of other controllers...

	Jeff


--

[ message continues ]

The problem is that when the M5229 is embedded into an M1543, the
PCI IRQ is ignored, and the IRQ is routed directly into the ISA-PIC
in the M1543. This routing is done via a different set of configuration
registers, so that each channel can have its own IRQ.

This means that in pci-native mode, there is no pcidev.irq field set,
as there is no PCI IRQ setup. Alan Cox has stated that this is too
broken to be worked around in libata.

-- 
Ben (ben@fluff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'
--

[ message continues ]