sh: Enable PCI66 support for SH7780 host controller.

This adds some helper glue for scanning the bus and determining if all
of the devices are 66MHz capable or not before flipping on 66MHz mode.
This isn't quite to spec, but it's fairly consistent with what other
embedded controllers end up having to do.

Scanning code cribbed from the MIPS txx9 PCI code.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/arch/sh/drivers/pci/common.c b/arch/sh/drivers/pci/common.c
new file mode 100644
index 000000000000..f67c946a8612
--- /dev/null
+++ b/arch/sh/drivers/pci/common.c
@@ -0,0 +1,64 @@
+#include <linux/pci.h>
+#include <linux/kernel.h>
+
+static int __init
+early_read_config_word(struct pci_channel *hose,
+		       int top_bus, int bus, int devfn, int offset, u16 *value)
+{
+	struct pci_dev fake_dev;
+	struct pci_bus fake_bus;
+
+	fake_dev.bus = &fake_bus;
+	fake_dev.sysdata = hose;
+	fake_dev.devfn = devfn;
+	fake_bus.number = bus;
+	fake_bus.sysdata = hose;
+	fake_bus.ops = hose->pci_ops;
+
+	if (bus != top_bus)
+		/* Fake a parent bus structure. */
+		fake_bus.parent = &fake_bus;
+	else
+		fake_bus.parent = NULL;
+
+	return pci_read_config_word(&fake_dev, offset, value);
+}
+
+int __init pci_is_66mhz_capable(struct pci_channel *hose,
+				int top_bus, int current_bus)
+{
+	u32 pci_devfn;
+	unsigned short vid;
+	int cap66 = -1;
+	u16 stat;
+
+	printk(KERN_INFO "PCI: Checking 66MHz capabilities...\n");
+
+	for (pci_devfn = 0; pci_devfn < 0xff; pci_devfn++) {
+		if (PCI_FUNC(pci_devfn))
+			continue;
+		if (early_read_config_word(hose, top_bus, current_bus,
+					   pci_devfn, PCI_VENDOR_ID, &vid) !=
+		    PCIBIOS_SUCCESSFUL)
+			continue;
+		if (vid == 0xffff)
+			continue;
+
+		/* check 66MHz capability */
+		if (cap66 < 0)
+			cap66 = 1;
+		if (cap66) {
+			early_read_config_word(hose, top_bus, current_bus,
+					       pci_devfn, PCI_STATUS, &stat);
+			if (!(stat & PCI_STATUS_66MHZ)) {
+				printk(KERN_DEBUG
+				       "PCI: %02x:%02x not 66MHz capable.\n",
+				       current_bus, pci_devfn);
+				cap66 = 0;
+				break;
+			}
+		}
+	}
+
+	return cap66 > 0;
+}