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_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 } 64 postcore_initcall(sdk7786_pci_init); 65