drivers/tty/serial/8250/8250_bcm2835aux.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Serial port driver for BCM2835AUX UART
   4  *
   5  * Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org>
   6  *
   7  * Based on 8250_lpc18xx.c:
   8  * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
   9  */
  10
  11 #include <linux/clk.h>
  12 #include <linux/io.h>
  13 #include <linux/module.h>
  14 #include <linux/of.h>
  15 #include <linux/platform_device.h>
  16
  17 #include "8250.h"
  18
  19 struct bcm2835aux_data {
  20         struct uart_8250_port uart;
  21         struct clk *clk;
  22         int line;
  23 };
  24
  25 static int bcm2835aux_serial_probe(struct platform_device *pdev)
  26 {
  27         struct bcm2835aux_data *data;
  28         struct resource *res;
  29         int ret;
  30
  31         /* allocate the custom structure */
  32         data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
  33         if (!data)
  34                 return -ENOMEM;
  35
  36         /* initialize data */
  37         spin_lock_init(&data->uart.port.lock);
  38         data->uart.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
  39         data->uart.port.dev = &pdev->dev;
  40         data->uart.port.regshift = 2;
  41         data->uart.port.type = PORT_16550;
  42         data->uart.port.iotype = UPIO_MEM;
  43         data->uart.port.fifosize = 8;
  44         data->uart.port.flags = UPF_SHARE_IRQ |
  45                                 UPF_FIXED_PORT |
  46                                 UPF_FIXED_TYPE |
  47                                 UPF_SKIP_TEST;
  48
  49         /* get the clock - this also enables the HW */
  50         data->clk = devm_clk_get(&pdev->dev, NULL);
  51         ret = PTR_ERR_OR_ZERO(data->clk);
  52         if (ret) {
  53                 dev_err(&pdev->dev, "could not get clk: %d\n", ret);
  54                 return ret;
  55         }
  56
  57         /* get the interrupt */
  58         ret = platform_get_irq(pdev, 0);
  59         if (ret < 0) {
  60                 dev_err(&pdev->dev, "irq not found - %i", ret);
  61                 return ret;
  62         }
  63         data->uart.port.irq = ret;
  64
  65         /* map the main registers */
  66         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  67         if (!res) {
  68                 dev_err(&pdev->dev, "memory resource not found");
  69                 return -EINVAL;
  70         }
  71         data->uart.port.membase = devm_ioremap_resource(&pdev->dev, res);
  72         ret = PTR_ERR_OR_ZERO(data->uart.port.membase);
  73         if (ret)
  74                 return ret;
  75
  76         /* Check for a fixed line number */
  77         ret = of_alias_get_id(pdev->dev.of_node, "serial");
  78         if (ret >= 0)
  79                 data->uart.port.line = ret;
  80
  81         /* enable the clock as a last step */
  82         ret = clk_prepare_enable(data->clk);
  83         if (ret) {
  84                 dev_err(&pdev->dev, "unable to enable uart clock - %d\n",
  85                         ret);
  86                 return ret;
  87         }
  88
  89         /* the HW-clock divider for bcm2835aux is 8,
  90          * but 8250 expects a divider of 16,
  91          * so we have to multiply the actual clock by 2
  92          * to get identical baudrates.
  93          */
  94         data->uart.port.uartclk = clk_get_rate(data->clk) * 2;
  95
  96         /* register the port */
  97         ret = serial8250_register_8250_port(&data->uart);
  98         if (ret < 0) {
  99                 dev_err(&pdev->dev, "unable to register 8250 port - %d\n",
 100                         ret);
 101                 goto dis_clk;
 102         }
 103         data->line = ret;
 104
 105         platform_set_drvdata(pdev, data);
 106
 107         return 0;
 108
 109 dis_clk:
 110         clk_disable_unprepare(data->clk);
 111         return ret;
 112 }
 113
 114 static int bcm2835aux_serial_remove(struct platform_device *pdev)
 115 {
 116         struct bcm2835aux_data *data = platform_get_drvdata(pdev);
 117
 118         serial8250_unregister_port(data->uart.port.line);
 119         clk_disable_unprepare(data->clk);
 120
 121         return 0;
 122 }
 123
 124 static const struct of_device_id bcm2835aux_serial_match[] = {
 125         { .compatible = "brcm,bcm2835-aux-uart" },
 126         { },
 127 };
 128 MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match);
 129
 130 static struct platform_driver bcm2835aux_serial_driver = {
 131         .driver = {
 132                 .name = "bcm2835-aux-uart",
 133                 .of_match_table = bcm2835aux_serial_match,
 134         },
 135         .probe  = bcm2835aux_serial_probe,
 136         .remove = bcm2835aux_serial_remove,
 137 };
 138 module_platform_driver(bcm2835aux_serial_driver);
 139
 140 MODULE_DESCRIPTION("BCM2835 auxiliar UART driver");
 141 MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
 142 MODULE_LICENSE("GPL v2");