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The AUX/mini-UART in the BCM2835 family of procesors is a cut-down 8250 clone. In particular it is lacking support for the following features: CSTOPB PARENB PARODD CMSPAR CS5 CS6 Add a new capability (UART_CAP_MINI) that exposes the restrictions to the user of the termios API by turning off the unsupported features in the request. N.B. It is almost possible to automatically discover the missing features by reading back the LCR register, but the CSIZE bits don't cooperate (contrary to the documentation, both bits are significant, but CS5 and CS6 are mapped to CS7) and the code is much longer. See: https://github.com/raspberrypi/linux/issues/1561 Signed-off-by: Phil Elwell <phil@raspberrypi.org> Acked-by: Eric Anholt <eric@anholt.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
147 lines
3.6 KiB
C
147 lines
3.6 KiB
C
/*
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* Serial port driver for BCM2835AUX UART
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*
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* Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org>
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*
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* Based on 8250_lpc18xx.c:
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* Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/clk.h>
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#include <linux/io.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include "8250.h"
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struct bcm2835aux_data {
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struct uart_8250_port uart;
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struct clk *clk;
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int line;
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};
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static int bcm2835aux_serial_probe(struct platform_device *pdev)
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{
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struct bcm2835aux_data *data;
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struct resource *res;
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int ret;
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/* allocate the custom structure */
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data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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/* initialize data */
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spin_lock_init(&data->uart.port.lock);
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data->uart.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
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data->uart.port.dev = &pdev->dev;
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data->uart.port.regshift = 2;
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data->uart.port.type = PORT_16550;
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data->uart.port.iotype = UPIO_MEM;
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data->uart.port.fifosize = 8;
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data->uart.port.flags = UPF_SHARE_IRQ |
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UPF_FIXED_PORT |
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UPF_FIXED_TYPE |
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UPF_SKIP_TEST;
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/* get the clock - this also enables the HW */
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data->clk = devm_clk_get(&pdev->dev, NULL);
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ret = PTR_ERR_OR_ZERO(data->clk);
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if (ret) {
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dev_err(&pdev->dev, "could not get clk: %d\n", ret);
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return ret;
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}
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/* get the interrupt */
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ret = platform_get_irq(pdev, 0);
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if (ret < 0) {
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dev_err(&pdev->dev, "irq not found - %i", ret);
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return ret;
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}
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data->uart.port.irq = ret;
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/* map the main registers */
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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if (!res) {
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dev_err(&pdev->dev, "memory resource not found");
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return -EINVAL;
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}
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data->uart.port.membase = devm_ioremap_resource(&pdev->dev, res);
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ret = PTR_ERR_OR_ZERO(data->uart.port.membase);
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if (ret)
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return ret;
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/* Check for a fixed line number */
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ret = of_alias_get_id(pdev->dev.of_node, "serial");
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if (ret >= 0)
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data->uart.port.line = ret;
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/* enable the clock as a last step */
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ret = clk_prepare_enable(data->clk);
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if (ret) {
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dev_err(&pdev->dev, "unable to enable uart clock - %d\n",
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ret);
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return ret;
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}
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/* the HW-clock divider for bcm2835aux is 8,
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* but 8250 expects a divider of 16,
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* so we have to multiply the actual clock by 2
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* to get identical baudrates.
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*/
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data->uart.port.uartclk = clk_get_rate(data->clk) * 2;
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/* register the port */
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ret = serial8250_register_8250_port(&data->uart);
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if (ret < 0) {
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dev_err(&pdev->dev, "unable to register 8250 port - %d\n",
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ret);
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goto dis_clk;
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}
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data->line = ret;
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platform_set_drvdata(pdev, data);
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return 0;
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dis_clk:
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clk_disable_unprepare(data->clk);
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return ret;
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}
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static int bcm2835aux_serial_remove(struct platform_device *pdev)
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{
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struct bcm2835aux_data *data = platform_get_drvdata(pdev);
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serial8250_unregister_port(data->uart.port.line);
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clk_disable_unprepare(data->clk);
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return 0;
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}
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static const struct of_device_id bcm2835aux_serial_match[] = {
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{ .compatible = "brcm,bcm2835-aux-uart" },
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{ },
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};
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MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match);
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static struct platform_driver bcm2835aux_serial_driver = {
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.driver = {
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.name = "bcm2835-aux-uart",
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.of_match_table = bcm2835aux_serial_match,
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},
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.probe = bcm2835aux_serial_probe,
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.remove = bcm2835aux_serial_remove,
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};
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module_platform_driver(bcm2835aux_serial_driver);
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MODULE_DESCRIPTION("BCM2835 auxiliar UART driver");
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MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
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MODULE_LICENSE("GPL v2");
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