1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (c) 2017 Intel Corporation
4 */
5
6 #include <common.h>
7 #include <dm.h>
8 #include <ns16550.h>
9 #include <serial.h>
10
11 /*
12 * The UART clock is calculated as
13 *
14 * UART clock = XTAL * UART_MUL / UART_DIV
15 *
16 * The baudrate is calculated as
17 *
18 * baud rate = UART clock / UART_PS / DLAB
19 */
20 #define UART_PS 0x30
21 #define UART_MUL 0x34
22 #define UART_DIV 0x38
23
mid_writel(struct ns16550_plat * plat,int offset,int value)24 static void mid_writel(struct ns16550_plat *plat, int offset, int value)
25 {
26 unsigned char *addr;
27
28 offset *= 1 << plat->reg_shift;
29 addr = (unsigned char *)plat->base + offset;
30
31 writel(value, addr + plat->reg_offset);
32 }
33
mid_serial_probe(struct udevice * dev)34 static int mid_serial_probe(struct udevice *dev)
35 {
36 struct ns16550_plat *plat = dev_get_plat(dev);
37
38 /*
39 * Initialize fractional divider correctly for Intel Edison
40 * platform.
41 *
42 * For backward compatibility we have to set initial DLAB value
43 * to 16 and speed to 115200 baud, where initial frequency is
44 * 29491200Hz, and XTAL frequency is 38.4MHz.
45 */
46 mid_writel(plat, UART_MUL, 96);
47 mid_writel(plat, UART_DIV, 125);
48 mid_writel(plat, UART_PS, 16);
49
50 return ns16550_serial_probe(dev);
51 }
52
53 static const struct udevice_id mid_serial_ids[] = {
54 { .compatible = "intel,mid-uart" },
55 {}
56 };
57
58 U_BOOT_DRIVER(serial_intel_mid) = {
59 .name = "serial_intel_mid",
60 .id = UCLASS_SERIAL,
61 .of_match = mid_serial_ids,
62 .of_to_plat = ns16550_serial_of_to_plat,
63 .plat_auto = sizeof(struct ns16550_plat),
64 .priv_auto = sizeof(struct ns16550),
65 .probe = mid_serial_probe,
66 .ops = &ns16550_serial_ops,
67 };
68