Linux Kernel  3.7.1
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virtex.c
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1 /*
2  * The platform specific code for virtex devices since a boot loader is not
3  * always used.
4  *
5  * (C) Copyright 2008 Xilinx, Inc.
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License version 2 as published
9  * by the Free Software Foundation.
10  */
11 
12 #include "ops.h"
13 #include "io.h"
14 #include "stdio.h"
15 
16 #define UART_DLL 0 /* Out: Divisor Latch Low */
17 #define UART_DLM 1 /* Out: Divisor Latch High */
18 #define UART_FCR 2 /* Out: FIFO Control Register */
19 #define UART_FCR_CLEAR_RCVR 0x02 /* Clear the RCVR FIFO */
20 #define UART_FCR_CLEAR_XMIT 0x04 /* Clear the XMIT FIFO */
21 #define UART_LCR 3 /* Out: Line Control Register */
22 #define UART_MCR 4 /* Out: Modem Control Register */
23 #define UART_MCR_RTS 0x02 /* RTS complement */
24 #define UART_MCR_DTR 0x01 /* DTR complement */
25 #define UART_LCR_DLAB 0x80 /* Divisor latch access bit */
26 #define UART_LCR_WLEN8 0x03 /* Wordlength: 8 bits */
27 
28 static int virtex_ns16550_console_init(void *devp)
29 {
30  unsigned char *reg_base;
31  u32 reg_shift, reg_offset, clk, spd;
32  u16 divisor;
33  int n;
34 
35  if (dt_get_virtual_reg(devp, (void **)&reg_base, 1) < 1)
36  return -1;
37 
38  n = getprop(devp, "reg-offset", &reg_offset, sizeof(reg_offset));
39  if (n == sizeof(reg_offset))
40  reg_base += reg_offset;
41 
42  n = getprop(devp, "reg-shift", &reg_shift, sizeof(reg_shift));
43  if (n != sizeof(reg_shift))
44  reg_shift = 0;
45 
46  n = getprop(devp, "current-speed", (void *)&spd, sizeof(spd));
47  if (n != sizeof(spd))
48  spd = 9600;
49 
50  /* should there be a default clock rate?*/
51  n = getprop(devp, "clock-frequency", (void *)&clk, sizeof(clk));
52  if (n != sizeof(clk))
53  return -1;
54 
55  divisor = clk / (16 * spd);
56 
57  /* Access baud rate */
58  out_8(reg_base + (UART_LCR << reg_shift), UART_LCR_DLAB);
59 
60  /* Baud rate based on input clock */
61  out_8(reg_base + (UART_DLL << reg_shift), divisor & 0xFF);
62  out_8(reg_base + (UART_DLM << reg_shift), divisor >> 8);
63 
64  /* 8 data, 1 stop, no parity */
65  out_8(reg_base + (UART_LCR << reg_shift), UART_LCR_WLEN8);
66 
67  /* RTS/DTR */
68  out_8(reg_base + (UART_MCR << reg_shift), UART_MCR_RTS | UART_MCR_DTR);
69 
70  /* Clear transmitter and receiver */
71  out_8(reg_base + (UART_FCR << reg_shift),
73  return 0;
74 }
75 
76 /* For virtex, the kernel may be loaded without using a bootloader and if so
77  some UARTs need more setup than is provided in the normal console init
78 */
80 {
81  void *devp;
82  char devtype[MAX_PROP_LEN];
83  char path[MAX_PATH_LEN];
84 
85  devp = finddevice("/chosen");
86  if (devp == NULL)
87  return -1;
88 
89  if (getprop(devp, "linux,stdout-path", path, MAX_PATH_LEN) > 0) {
90  devp = finddevice(path);
91  if (devp == NULL)
92  return -1;
93 
94  if ((getprop(devp, "device_type", devtype, sizeof(devtype)) > 0)
95  && !strcmp(devtype, "serial")
96  && (dt_is_compatible(devp, "ns16550")))
97  virtex_ns16550_console_init(devp);
98  }
99  return 0;
100 }