1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * SDK7786 FPGA PCIe mux handling
4 *
5 * Copyright (C) 2010 Paul Mundt
6 */
7 #define pr_fmt(fmt) "PCI: " fmt
8
9 #include <linux/init.h>
10 #include <linux/kernel.h>
11 #include <linux/pci.h>
12 #include <mach/fpga.h>
13
14 /*
15 * The SDK7786 FPGA supports mangling of most of the slots in some way or
16 * another. Slots 3/4 are special in that only one can be supported at a
17 * time, and both appear on port 3 to the PCI bus scan. Enabling slot 4
18 * (the horizontal edge connector) will disable slot 3 entirely.
19 *
20 * Misconfigurations can be detected through the FPGA via the slot
21 * resistors to determine card presence. Hotplug remains unsupported.
22 */
23 static unsigned int slot4en __initdata;
24
25 char *__init pcibios_setup(char *str)
26 {
27 if (strcmp(str, "slot4en") == 0) {
28 slot4en = 1;
29 return NULL;
30 }
31
32 return str;
33 }
34
35 static int __init sdk7786_pci_init(void)
36 {
37 u16 data = fpga_read_reg(PCIECR);
38
39 /*
40 * Enable slot #4 if it's been specified on the command line.
41 *
42 * Optionally reroute if slot #4 has a card present while slot #3
43 * does not, regardless of command line value.
44 *
45 * Card presence is logically inverted.
46 */
47 slot4en ?: (!(data & PCIECR_PRST4) && (data & PCIECR_PRST3));
48 if (slot4en) {
49 pr_info("Activating PCIe slot#4 (disabling slot#3)\n");
50
51 data &= ~PCIECR_PCIEMUX1;
52 fpga_write_reg(data, PCIECR);
53
54 /* Warn about forced rerouting if slot#3 is occupied */
55 if ((data & PCIECR_PRST3) == 0) {
56 pr_warning("Unreachable card detected in slot#3\n");
57 return -EBUSY;
58 }
59 } else
60 pr_info("PCIe slot#4 disabled\n");
61
62 return 0;
63 }
64 postcore_initcall(sdk7786_pci_init);