src/superio/smsc/lpc47n207/early_serial.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <arch/io.h>
   4 #include <device/pnp.h>
   5 #include <stdint.h>
   6
   7 #include "lpc47n207.h"
   8
   9 /*
  10  * This code tries to discover the SMSC LPC47N207 superio chip which can be
  11  * connected over an LPC dongle. The chip could be bootstrap mapped to one of
  12  * four LPC addresses: 0x2e, 0x4e, 0x162e, and 0x164e.
  13  *
  14  * Initializing the UART requires accesses to a few control registers. This
  15  * structure includes the register offset and the value to write (along with
  16  * the mask).
  17  */
  18 typedef struct {
  19         u8 conf_reg;
  20         u8 value;
  21         u8 mask;
  22 } uart_conf;
  23
  24 /* All regs/values to write to initialize the LPC47N207 UART */
  25 static const uart_conf uart_conf_data [] = {
  26         {2, (1 << 3), (1 << 3)},    /* cr02, enable Primary UART power */
  27         {0xc, (1 << 6), (1 << 6)},  /* cr0c, enable Primary UART high speed */
  28         {0x24, (CONFIG_TTYS0_BASE >> 3) << 1, 0xff},  /* cr24, base addr */
  29 };
  30
  31 void try_enabling_LPC47N207_uart(void)
  32 {
  33         u8 reg_value;
  34         const uart_conf* conf_item;
  35         u16 lpc_ports[] = {0x2e, 0x4e, 0x162e, 0x164e};
  36         u16 lpc_port;
  37         int i, j;
  38
  39 #define CONF_ENABLE    0x55
  40 #define CONF_DISABLE   0xaa
  41
  42         for (j = 0; j < ARRAY_SIZE(lpc_ports); j++) {
  43                 lpc_port = lpc_ports[j];
  44
  45                 /* enable CONFIG mode */
  46                 outb(CONF_ENABLE, lpc_port);
  47                 reg_value = inb(lpc_port);
  48                 if (reg_value != CONF_ENABLE) {
  49                         continue; /* There is no LPC device at this address */
  50                 }
  51
  52                 do {
  53                         /*
  54                          * Registers 12 and 13 hold config address, look for a
  55                          * match.
  56                          */
  57                         outb(0x12, lpc_port);
  58                         reg_value = inb(lpc_port + 1);
  59                         if (reg_value != (lpc_port & 0xff))
  60                                 break;
  61
  62                         outb(0x13, lpc_port);
  63                         reg_value = inb(lpc_port + 1);
  64                         if (reg_value != (lpc_port >> 8))
  65                                 break;
  66
  67                         /* This must be the SMSC LPC 47N207, enable the UART. */
  68                         for (i = 0; i < ARRAY_SIZE(uart_conf_data); i++) {
  69                                 u8 reg, value, mask;
  70
  71                                 conf_item = uart_conf_data + i;
  72
  73                                 reg = conf_item->conf_reg;
  74                                 value = conf_item->value;
  75                                 mask = conf_item->mask;
  76
  77                                 outb(reg, lpc_port);
  78                                 reg_value = inb(lpc_port + 1);
  79                                 reg_value &= ~mask;
  80                                 reg_value |= (value & mask);
  81                                 outb(reg_value, lpc_port + 1);
  82                         }
  83                 } while (0);
  84                 outb(CONF_DISABLE, lpc_port);
  85         }
  86 }