sh: pci: Support root complex config accesses on SH7786 PCIe.

The SH7786 PCIe is presently unable to enumerate itself in root complex
mode, and has no visibility through either type 0 or type 1 accesses,
despite having a mostly sensible extended config space for each port.
Attempts to generate type 0 or type 1 config cycles result in completer
aborts, so we're ultimately forced to use SuperHyway transactions
instead.

As each port has a single port <-> device mapping that resolves for any
PCI_SLOT definition, we simply hijack devfn 0 for the SuperHyway
transaction and bump up the devfn limit.

With enumeration of the root complex now possible, we also need to insert
an early fixup to hide the BARs from the kernel. With all of that done,
it's now possible to use the pcieport services with all of the PCIe
ports, which is the first step to power management support.

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

1 files changed, 31 insertions, 4 deletions

diff --git a/arch/sh/drivers/pci/ops-sh7786.c b/arch/sh/drivers/pci/ops-sh7786.c
index 4728199f71a6..01cb70fbd803 100644
--- a/arch/sh/drivers/pci/ops-sh7786.c
+++ b/arch/sh/drivers/pci/ops-sh7786.c
@@ -25,23 +25,49 @@ static int sh7786_pcie_config_access(unsigned char access_type,
 		struct pci_bus *bus, unsigned int devfn, int where, u32 *data)
 {
 	struct pci_channel *chan = bus->sysdata;
-	int dev, func, type;
+	int dev, func, type, reg;
 
 	dev = PCI_SLOT(devfn);
 	func = PCI_FUNC(devfn);
 	type = !!bus->parent;
+	reg = where & ~3;
 
 	if (bus->number > 255 || dev > 31 || func > 7)
 		return PCIBIOS_FUNC_NOT_SUPPORTED;
-	if (bus->parent == NULL && dev)
-		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	/*
+	 * While each channel has its own memory-mapped extended config
+	 * space, it's generally only accessible when in endpoint mode.
+	 * When in root complex mode, the controller is unable to target
+	 * itself with either type 0 or type 1 accesses, and indeed, any
+	 * controller initiated target transfer to its own config space
+	 * result in a completer abort.
+	 *
+	 * Each channel effectively only supports a single device, but as
+	 * the same channel <-> device access works for any PCI_SLOT()
+	 * value, we cheat a bit here and bind the controller's config
+	 * space to devfn 0 in order to enable self-enumeration. In this
+	 * case the regular PAR/PDR path is sidelined and the mangled
+	 * config access itself is initiated as a SuperHyway transaction.
+	 */
+	if (pci_is_root_bus(bus)) {
+		if (dev == 0) {
+			if (access_type == PCI_ACCESS_READ)
+				*data = pci_read_reg(chan, PCI_REG(reg));
+			else
+				pci_write_reg(chan, *data, PCI_REG(reg));
+
+			return PCIBIOS_SUCCESSFUL;
+		} else if (dev > 1)
+			return PCIBIOS_DEVICE_NOT_FOUND;
+	}
 
 	/* Clear errors */
 	pci_write_reg(chan, pci_read_reg(chan, SH4A_PCIEERRFR), SH4A_PCIEERRFR);
 
 	/* Set the PIO address */
 	pci_write_reg(chan, (bus->number << 24) | (dev << 19) |
-				(func << 16) | (where & ~3), SH4A_PCIEPAR);
+				(func << 16) | reg, SH4A_PCIEPAR);
 
 	/* Enable the configuration access */
 	pci_write_reg(chan, (1 << 31) | (type << 8), SH4A_PCIEPCTLR);
@@ -49,6 +75,7 @@ static int sh7786_pcie_config_access(unsigned char access_type,
 	/* Check for errors */
 	if (pci_read_reg(chan, SH4A_PCIEERRFR) & 0x10)
 		return PCIBIOS_DEVICE_NOT_FOUND;
+
 	/* Check for master and target aborts */
 	if (pci_read_reg(chan, SH4A_PCIEPCICONF1) & ((1 << 29) | (1 << 28)))
 		return PCIBIOS_DEVICE_NOT_FOUND;