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"Das U-Boot" Source Tree
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * UART support for U-Boot when launched from Coreboot
4 *
5 * Copyright 2019 Google LLC
6 */
7
8#define LOG_CATGEGORY UCLASS_SERIAL
9
10#include <dm.h>
11#include <log.h>
12#include <ns16550.h>
13#include <serial.h>
14#include <acpi/acpi_table.h>
15#include <asm/cb_sysinfo.h>
16
17DECLARE_GLOBAL_DATA_PTR;
18
19static int read_dbg2(struct ns16550_plat *plat)
20{
21 struct acpi_table_header *tab;
22 struct acpi_dbg2_header *hdr;
23 struct acpi_dbg2_device *dbg;
24 struct acpi_gen_regaddr *addr;
25 u32 *addr_size;
26
27 log_debug("Looking for DBG2 in ACPI tables\n");
28 if (!gd->acpi_start) {
29 log_debug("No ACPI tables\n");
30 return -ENOENT;
31 }
32
33 tab = acpi_find_table("DBG2");
34 if (!tab) {
35 log_debug("No DBG2 table\n");
36 return -ENOENT;
37 }
38 hdr = container_of(tab, struct acpi_dbg2_header, header);
39
40 /* We only use the first device, but check that there is at least one */
41 if (!hdr->devices_count) {
42 log_debug("No devices\n");
43 return -ENOENT;
44 }
45 if (hdr->devices_offset >= tab->length) {
46 log_debug("Invalid offset\n");
47 return -EINVAL;
48 }
49 dbg = (void *)hdr + hdr->devices_offset;
50 if (dbg->revision) {
51 log_debug("Invalid revision %d\n", dbg->revision);
52 return -EINVAL;
53 }
54 if (!dbg->address_count) {
55 log_debug("No addresses\n");
56 return -EINVAL;
57 }
58 if (dbg->port_type != ACPI_DBG2_SERIAL_PORT) {
59 log_debug("Not a serial port\n");
60 return -EPROTOTYPE;
61 }
62 if (dbg->port_subtype != ACPI_DBG2_16550_COMPATIBLE) {
63 log_debug("Incompatible serial port\n");
64 return -EPROTOTYPE;
65 }
66 if (dbg->base_address_offset >= dbg->length ||
67 dbg->address_size_offset >= dbg->length) {
68 log_debug("Invalid base address/size offsets %d, %d\n",
69 dbg->base_address_offset, dbg->address_size_offset);
70 return -EINVAL;
71 }
72 addr_size = (void *)dbg + dbg->address_size_offset;
73 if (!*addr_size) {
74 log_debug("Zero address size\n");
75 return -EINVAL;
76 }
77 addr = (void *)dbg + dbg->base_address_offset;
78 if (addr->space_id != ACPI_ADDRESS_SPACE_MEMORY) {
79 log_debug("Incompatible space %d\n", addr->space_id);
80 return -EPROTOTYPE;
81 }
82
83 plat->base = addr->addrl;
84
85 /* ACPI_ACCESS_SIZE_DWORD_ACCESS is 3; we want 2 */
86 plat->reg_shift = addr->access_size - 1;
87 plat->reg_width = 4; /* coreboot sets bit_width to 0 */
88 plat->clock = 1843200;
89 plat->fcr = UART_FCR_DEFVAL;
90 plat->flags = 0;
91 log_debug("Collected UART from ACPI DBG2 table\n");
92
93 return 0;
94}
95
96static int coreboot_of_to_plat(struct udevice *dev)
97{
98 struct ns16550_plat *plat = dev_get_plat(dev);
99 struct cb_serial *cb_info = lib_sysinfo.serial;
100 int ret = -ENOENT;
101
102 if (cb_info) {
103 plat->base = cb_info->baseaddr;
104 plat->reg_shift = cb_info->regwidth == 4 ? 2 : 0;
105 plat->reg_width = cb_info->regwidth;
106 plat->clock = cb_info->input_hertz;
107 plat->fcr = UART_FCR_DEFVAL;
108 plat->flags = 0;
109 if (cb_info->type == CB_SERIAL_TYPE_IO_MAPPED)
110 plat->flags |= NS16550_FLAG_IO;
111 ret = 0;
112 } else if (IS_ENABLED(CONFIG_COREBOOT_SERIAL_FROM_DBG2)) {
113 ret = read_dbg2(plat);
114 }
115
116 if (ret) {
117 /*
118 * Returning an error will cause U-Boot to complain that
119 * there is no UART, which may panic. So stay silent and
120 * pray that the video console will work.
121 */
122 log_debug("Cannot detect UART\n");
123 }
124
125 return 0;
126}
127
128static const struct udevice_id coreboot_serial_ids[] = {
129 { .compatible = "coreboot-serial" },
130 { },
131};
132
133U_BOOT_DRIVER(coreboot_uart) = {
134 .name = "coreboot_uart",
135 .id = UCLASS_SERIAL,
136 .of_match = coreboot_serial_ids,
137 .priv_auto = sizeof(struct ns16550),
138 .plat_auto = sizeof(struct ns16550_plat),
139 .of_to_plat = coreboot_of_to_plat,
140 .probe = ns16550_serial_probe,
141 .ops = &ns16550_serial_ops,
142 .flags = DM_FLAG_PRE_RELOC,
143};