1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Primary to Sideband (P2SB) bridge access support 4 * 5 * Copyright (c) 2017, 2021-2022 Intel Corporation. 6 * 7 * Authors: Andy Shevchenko <andriy.shevchenko@linux.intel.com> 8 * Jonathan Yong <jonathan.yong@intel.com> 9 */ 10 11 #include <linux/bits.h> 12 #include <linux/export.h> 13 #include <linux/pci.h> 14 #include <linux/platform_data/x86/p2sb.h> 15 16 #include <asm/cpu_device_id.h> 17 #include <asm/intel-family.h> 18 19 #define P2SBC 0xe0 20 #define P2SBC_HIDE BIT(8) 21 22 #define P2SB_DEVFN_DEFAULT PCI_DEVFN(31, 1) 23 24 static const struct x86_cpu_id p2sb_cpu_ids[] = { 25 X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT, PCI_DEVFN(13, 0)), 26 {} 27 }; 28 29 static int p2sb_get_devfn(unsigned int *devfn) 30 { 31 unsigned int fn = P2SB_DEVFN_DEFAULT; 32 const struct x86_cpu_id *id; 33 34 id = x86_match_cpu(p2sb_cpu_ids); 35 if (id) 36 fn = (unsigned int)id->driver_data; 37 38 *devfn = fn; 39 return 0; 40 } 41 42 /* Copy resource from the first BAR of the device in question */ 43 static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem) 44 { 45 struct resource *bar0 = &pdev->resource[0]; 46 47 /* Make sure we have no dangling pointers in the output */ 48 memset(mem, 0, sizeof(*mem)); 49 50 /* 51 * We copy only selected fields from the original resource. 52 * Because a PCI device will be removed soon, we may not use 53 * any allocated data, hence we may not copy any pointers. 54 */ 55 mem->start = bar0->start; 56 mem->end = bar0->end; 57 mem->flags = bar0->flags; 58 mem->desc = bar0->desc; 59 60 return 0; 61 } 62 63 static int p2sb_scan_and_read(struct pci_bus *bus, unsigned int devfn, struct resource *mem) 64 { 65 struct pci_dev *pdev; 66 int ret; 67 68 pdev = pci_scan_single_device(bus, devfn); 69 if (!pdev) 70 return -ENODEV; 71 72 ret = p2sb_read_bar0(pdev, mem); 73 74 pci_stop_and_remove_bus_device(pdev); 75 return ret; 76 } 77 78 /** 79 * p2sb_bar - Get Primary to Sideband (P2SB) bridge device BAR 80 * @bus: PCI bus to communicate with 81 * @devfn: PCI slot and function to communicate with 82 * @mem: memory resource to be filled in 83 * 84 * The BIOS prevents the P2SB device from being enumerated by the PCI 85 * subsystem, so we need to unhide and hide it back to lookup the BAR. 86 * 87 * if @bus is NULL, the bus 0 in domain 0 will be used. 88 * If @devfn is 0, it will be replaced by devfn of the P2SB device. 89 * 90 * Caller must provide a valid pointer to @mem. 91 * 92 * Locking is handled by pci_rescan_remove_lock mutex. 93 * 94 * Return: 95 * 0 on success or appropriate errno value on error. 96 */ 97 int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem) 98 { 99 struct pci_dev *pdev_p2sb; 100 unsigned int devfn_p2sb; 101 u32 value = P2SBC_HIDE; 102 int ret; 103 104 /* Get devfn for P2SB device itself */ 105 ret = p2sb_get_devfn(&devfn_p2sb); 106 if (ret) 107 return ret; 108 109 /* if @bus is NULL, use bus 0 in domain 0 */ 110 bus = bus ?: pci_find_bus(0, 0); 111 112 /* 113 * Prevent concurrent PCI bus scan from seeing the P2SB device and 114 * removing via sysfs while it is temporarily exposed. 115 */ 116 pci_lock_rescan_remove(); 117 118 /* Unhide the P2SB device, if needed */ 119 pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value); 120 if (value & P2SBC_HIDE) 121 pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0); 122 123 pdev_p2sb = pci_scan_single_device(bus, devfn_p2sb); 124 if (devfn) 125 ret = p2sb_scan_and_read(bus, devfn, mem); 126 else 127 ret = p2sb_read_bar0(pdev_p2sb, mem); 128 pci_stop_and_remove_bus_device(pdev_p2sb); 129 130 /* Hide the P2SB device, if it was hidden */ 131 if (value & P2SBC_HIDE) 132 pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE); 133 134 pci_unlock_rescan_remove(); 135 136 if (ret) 137 return ret; 138 139 if (mem->flags == 0) 140 return -ENODEV; 141 142 return 0; 143 } 144 EXPORT_SYMBOL_GPL(p2sb_bar); 145