LXR uboot/drivers/serial/serial_intel

   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
  24static void mid_writel(struct ns16550_platdata *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
  34static int mid_serial_probe(struct udevice *dev)
  35{
  36        struct ns16550_platdata *plat = dev_get_platdata(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
  53static const struct udevice_id mid_serial_ids[] = {
  54        { .compatible = "intel,mid-uart" },
  55        {}
  56};
  57
  58U_BOOT_DRIVER(serial_intel_mid) = {
  59        .name   = "serial_intel_mid",
  60        .id     = UCLASS_SERIAL,
  61        .of_match = mid_serial_ids,
  62        .ofdata_to_platdata = ns16550_serial_ofdata_to_platdata,
  63        .platdata_auto_alloc_size = sizeof(struct ns16550_platdata),
  64        .priv_auto_alloc_size = sizeof(struct NS16550),
  65        .probe  = mid_serial_probe,
  66        .ops    = &ns16550_serial_ops,
  67};
  68