sh: pci: Support slot 4 routing on SDK7786.

SDK7786 supports connecting either slot3 or 4 to the same PCIe port by
way of FPGA muxing. By default the vertical slot 3 on the baseboard is
enabled, so this adds in a command line option for forcibly enabling the
slot 4 edge connector.

If nothing has been specified on the command line, we fall back to
reading the resistor values for card presence to figure out where to
route the port to.

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

1 files changed, 68 insertions, 0 deletions

diff --git a/arch/sh/drivers/pci/fixups-sdk7786.c b/arch/sh/drivers/pci/fixups-sdk7786.c
new file mode 100644
index 000000000000..058a65a1aa20
--- /dev/null
+++ b/arch/sh/drivers/pci/fixups-sdk7786.c
@@ -0,0 +1,68 @@
+/*
+ * SDK7786 FPGA PCIe mux handling
+ *
+ * Copyright (C) 2010  Paul Mundt
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#define pr_fmt(fmt) "PCI: " fmt
+
+#include <linux/init.h>
+#include <linux/clk.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <mach/fpga.h>
+
+/*
+ * The SDK7786 FPGA supports mangling of most of the slots in some way or
+ * another. Slots 3/4 are special in that only one can be supported at a
+ * time, and both appear on port 3 to the PCI bus scan. Enabling slot 4
+ * (the horizontal edge connector) will disable slot 3 entirely.
+ *
+ * Misconfigurations can be detected through the FPGA via the slot
+ * resistors to determine card presence. Hotplug remains unsupported.
+ */
+static unsigned int slot4en __devinitdata;
+
+char *__devinit pcibios_setup(char *str)
+{
+	if (strcmp(str, "slot4en") == 0) {
+		slot4en = 1;
+		return NULL;
+	}
+
+	return str;
+}
+
+static int __init sdk7786_pci_init(void)
+{
+	u16 data = fpga_read_reg(PCIECR);
+
+	/*
+	 * Enable slot #4 if it's been specified on the command line.
+	 *
+	 * Optionally reroute if slot #4 has a card present while slot #3
+	 * does not, regardless of command line value.
+	 *
+	 * Card presence is logically inverted.
+	 */
+	slot4en ?: (!(data & PCIECR_PRST4) && (data & PCIECR_PRST3));
+	if (slot4en) {
+		pr_info("Activating PCIe slot#4 (disabling slot#3)\n");
+
+		data &= ~PCIECR_PCIEMUX1;
+		fpga_write_reg(data, PCIECR);
+
+		/* Warn about forced rerouting if slot#3 is occupied */
+		if ((data & PCIECR_PRST3) == 0) {
+			pr_warning("Unreachable card detected in slot#3\n");
+			return -EBUSY;
+		}
+	} else
+		pr_info("PCIe slot#4 disabled\n");
+
+	return 0;
+}
+postcore_initcall(sdk7786_pci_init);