arch/sh/drivers/pci/fixups-sdk7786.c

   1 /*
   2  * SDK7786 FPGA PCIe mux handling
   3  *
   4  * Copyright (C) 2010  Paul Mundt
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  */
  10 #define pr_fmt(fmt) "PCI: " fmt
  11
  12 #include <linux/init.h>
  13 #include <linux/kernel.h>
  14 #include <linux/pci.h>
  15 #include <mach/fpga.h>
  16
  17 /*
  18  * The SDK7786 FPGA supports mangling of most of the slots in some way or
  19  * another. Slots 3/4 are special in that only one can be supported at a
  20  * time, and both appear on port 3 to the PCI bus scan. Enabling slot 4
  21  * (the horizontal edge connector) will disable slot 3 entirely.
  22  *
  23  * Misconfigurations can be detected through the FPGA via the slot
  24  * resistors to determine card presence. Hotplug remains unsupported.
  25  */
  26 static unsigned int slot4en __initdata;
  27
  28 char *__init pcibios_setup(char *str)
  29 {
  30         if (strcmp(str, "slot4en") == 0) {
  31                 slot4en = 1;
  32                 return NULL;
  33         }
  34
  35         return str;
  36 }
  37
  38 static int __init sdk7786_pci_init(void)
  39 {
  40         u16 data = fpga_read_reg(PCIECR);
  41
  42         /*
  43          * Enable slot #4 if it's been specified on the command line.
  44          *
  45          * Optionally reroute if slot #4 has a card present while slot #3
  46          * does not, regardless of command line value.
  47          *
  48          * Card presence is logically inverted.
  49          */
  50         slot4en ?: (!(data & PCIECR_PRST4) && (data & PCIECR_PRST3));
  51         if (slot4en) {
  52                 pr_info("Activating PCIe slot#4 (disabling slot#3)\n");
  53
  54                 data &= ~PCIECR_PCIEMUX1;
  55                 fpga_write_reg(data, PCIECR);
  56
  57                 /* Warn about forced rerouting if slot#3 is occupied */
  58                 if ((data & PCIECR_PRST3) == 0) {
  59                         pr_warning("Unreachable card detected in slot#3\n");
  60                         return -EBUSY;
  61                 }
  62         } else
  63                 pr_info("PCIe slot#4 disabled\n");
  64
  65         return 0;
  66 }
  67 postcore_initcall(sdk7786_pci_init);