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 static const struct x86_cpu_id p2sb_cpu_ids[] = { 23 X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT, PCI_DEVFN(13, 0)), 24 X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT_D, PCI_DEVFN(31, 1)), 25 X86_MATCH_INTEL_FAM6_MODEL(ATOM_SILVERMONT_D, PCI_DEVFN(31, 1)), 26 X86_MATCH_INTEL_FAM6_MODEL(KABYLAKE, PCI_DEVFN(31, 1)), 27 X86_MATCH_INTEL_FAM6_MODEL(KABYLAKE_L, PCI_DEVFN(31, 1)), 28 X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE, PCI_DEVFN(31, 1)), 29 X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE_L, PCI_DEVFN(31, 1)), 30 {} 31 }; 32 33 static int p2sb_get_devfn(unsigned int *devfn) 34 { 35 const struct x86_cpu_id *id; 36 37 id = x86_match_cpu(p2sb_cpu_ids); 38 if (!id) 39 return -ENODEV; 40 41 *devfn = (unsigned int)id->driver_data; 42 return 0; 43 } 44 45 /* Copy resource from the first BAR of the device in question */ 46 static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem) 47 { 48 struct resource *bar0 = &pdev->resource[0]; 49 50 /* Make sure we have no dangling pointers in the output */ 51 memset(mem, 0, sizeof(*mem)); 52 53 /* 54 * We copy only selected fields from the original resource. 55 * Because a PCI device will be removed soon, we may not use 56 * any allocated data, hence we may not copy any pointers. 57 */ 58 mem->start = bar0->start; 59 mem->end = bar0->end; 60 mem->flags = bar0->flags; 61 mem->desc = bar0->desc; 62 63 return 0; 64 } 65 66 static int p2sb_scan_and_read(struct pci_bus *bus, unsigned int devfn, struct resource *mem) 67 { 68 struct pci_dev *pdev; 69 int ret; 70 71 pdev = pci_scan_single_device(bus, devfn); 72 if (!pdev) 73 return -ENODEV; 74 75 ret = p2sb_read_bar0(pdev, mem); 76 77 pci_stop_and_remove_bus_device(pdev); 78 return ret; 79 } 80 81 /** 82 * p2sb_bar - Get Primary to Sideband (P2SB) bridge device BAR 83 * @bus: PCI bus to communicate with 84 * @devfn: PCI slot and function to communicate with 85 * @mem: memory resource to be filled in 86 * 87 * The BIOS prevents the P2SB device from being enumerated by the PCI 88 * subsystem, so we need to unhide and hide it back to lookup the BAR. 89 * 90 * if @bus is NULL, the bus 0 in domain 0 will be used. 91 * If @devfn is 0, it will be replaced by devfn of the P2SB device. 92 * 93 * Caller must provide a valid pointer to @mem. 94 * 95 * Locking is handled by pci_rescan_remove_lock mutex. 96 * 97 * Return: 98 * 0 on success or appropriate errno value on error. 99 */ 100 int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem) 101 { 102 struct pci_dev *pdev_p2sb; 103 unsigned int devfn_p2sb; 104 u32 value = P2SBC_HIDE; 105 int ret; 106 107 /* Get devfn for P2SB device itself */ 108 ret = p2sb_get_devfn(&devfn_p2sb); 109 if (ret) 110 return ret; 111 112 /* if @bus is NULL, use bus 0 in domain 0 */ 113 bus = bus ?: pci_find_bus(0, 0); 114 115 /* 116 * Prevent concurrent PCI bus scan from seeing the P2SB device and 117 * removing via sysfs while it is temporarily exposed. 118 */ 119 pci_lock_rescan_remove(); 120 121 /* Unhide the P2SB device, if needed */ 122 pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value); 123 if (value & P2SBC_HIDE) 124 pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0); 125 126 pdev_p2sb = pci_scan_single_device(bus, devfn_p2sb); 127 if (devfn) 128 ret = p2sb_scan_and_read(bus, devfn, mem); 129 else 130 ret = p2sb_read_bar0(pdev_p2sb, mem); 131 pci_stop_and_remove_bus_device(pdev_p2sb); 132 133 /* Hide the P2SB device, if it was hidden */ 134 if (value & P2SBC_HIDE) 135 pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE); 136 137 pci_unlock_rescan_remove(); 138 139 if (ret) 140 return ret; 141 142 if (mem->flags == 0) 143 return -ENODEV; 144 145 return 0; 146 } 147 EXPORT_SYMBOL_GPL(p2sb_bar); 148