fixups-sdk7786.c

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/*
 * 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/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 __initdata;

char *__init 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);