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 */
23static unsigned int slot4en __initdata;
24
25char *__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
35static 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_warn("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}
64postcore_initcall(sdk7786_pci_init);
65