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/clk.h>
14 #include <linux/kernel.h>
15 #include <linux/pci.h>
16 #include <mach/fpga.h>
17 
18 /*
19  * The SDK7786 FPGA supports mangling of most of the slots in some way or
20  * another. Slots 3/4 are special in that only one can be supported at a
21  * time, and both appear on port 3 to the PCI bus scan. Enabling slot 4
22  * (the horizontal edge connector) will disable slot 3 entirely.
23  *
24  * Misconfigurations can be detected through the FPGA via the slot
25  * resistors to determine card presence. Hotplug remains unsupported.
26  */
27 static unsigned int slot4en __devinitdata;
28 
29 char *__devinit pcibios_setup(char *str)
30 {
31 	if (strcmp(str, "slot4en") == 0) {
32 		slot4en = 1;
33 		return NULL;
34 	}
35 
36 	return str;
37 }
38 
39 static int __init sdk7786_pci_init(void)
40 {
41 	u16 data = fpga_read_reg(PCIECR);
42 
43 	/*
44 	 * Enable slot #4 if it's been specified on the command line.
45 	 *
46 	 * Optionally reroute if slot #4 has a card present while slot #3
47 	 * does not, regardless of command line value.
48 	 *
49 	 * Card presence is logically inverted.
50 	 */
51 	slot4en ?: (!(data & PCIECR_PRST4) && (data & PCIECR_PRST3));
52 	if (slot4en) {
53 		pr_info("Activating PCIe slot#4 (disabling slot#3)\n");
54 
55 		data &= ~PCIECR_PCIEMUX1;
56 		fpga_write_reg(data, PCIECR);
57 
58 		/* Warn about forced rerouting if slot#3 is occupied */
59 		if ((data & PCIECR_PRST3) == 0) {
60 			pr_warning("Unreachable card detected in slot#3\n");
61 			return -EBUSY;
62 		}
63 	} else
64 		pr_info("PCIe slot#4 disabled\n");
65 
66 	return 0;
67 }
68 postcore_initcall(sdk7786_pci_init);
69