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 __devinitdata;
27 
28 char *__devinit 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);
68