1 files changed, 257 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
new file mode 100644
index 000000000..4f4502fb5
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Serial port driver for BCM2835AUX UART
+ *
+ * Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org>
+ *
+ * Based on 8250_lpc18xx.c:
+ * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
+ *
+ * The bcm2835aux is capable of RTS auto flow-control, but this driver doesn't
+ * take advantage of it yet.  When adding support, be sure not to enable it
+ * simultaneously to rs485.
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#include "8250.h"
+
+#define BCM2835_AUX_UART_CNTL		8
+#define BCM2835_AUX_UART_CNTL_RXEN	0x01 /* Receiver enable */
+#define BCM2835_AUX_UART_CNTL_TXEN	0x02 /* Transmitter enable */
+#define BCM2835_AUX_UART_CNTL_AUTORTS	0x04 /* RTS set by RX fill level */
+#define BCM2835_AUX_UART_CNTL_AUTOCTS	0x08 /* CTS stops transmitter */
+#define BCM2835_AUX_UART_CNTL_RTS3	0x00 /* RTS set until 3 chars left */
+#define BCM2835_AUX_UART_CNTL_RTS2	0x10 /* RTS set until 2 chars left */
+#define BCM2835_AUX_UART_CNTL_RTS1	0x20 /* RTS set until 1 chars left */
+#define BCM2835_AUX_UART_CNTL_RTS4	0x30 /* RTS set until 4 chars left */
+#define BCM2835_AUX_UART_CNTL_RTSINV	0x40 /* Invert auto RTS polarity */
+#define BCM2835_AUX_UART_CNTL_CTSINV	0x80 /* Invert auto CTS polarity */
+
+/**
+ * struct bcm2835aux_data - driver private data of BCM2835 auxiliary UART
+ * @clk: clock producer of the port's uartclk
+ * @line: index of the port's serial8250_ports[] entry
+ * @cntl: cached copy of CNTL register
+ */
+struct bcm2835aux_data {
+	struct clk *clk;
+	int line;
+	u32 cntl;
+};
+
+struct bcm2835_aux_serial_driver_data {
+	resource_size_t offset;
+};
+
+static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up)
+{
+	if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
+		struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev);
+
+		data->cntl &= ~BCM2835_AUX_UART_CNTL_RXEN;
+		serial_out(up, BCM2835_AUX_UART_CNTL, data->cntl);
+	}
+
+	/*
+	 * On the bcm2835aux, the MCR register contains no other
+	 * flags besides RTS.  So no need for a read-modify-write.
+	 */
+	if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND)
+		serial8250_out_MCR(up, 0);
+	else
+		serial8250_out_MCR(up, UART_MCR_RTS);
+}
+
+static void bcm2835aux_rs485_stop_tx(struct uart_8250_port *up)
+{
+	if (up->port.rs485.flags & SER_RS485_RTS_AFTER_SEND)
+		serial8250_out_MCR(up, 0);
+	else
+		serial8250_out_MCR(up, UART_MCR_RTS);
+
+	if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
+		struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev);
+
+		data->cntl |= BCM2835_AUX_UART_CNTL_RXEN;
+		serial_out(up, BCM2835_AUX_UART_CNTL, data->cntl);
+	}
+}
+
+static int bcm2835aux_serial_probe(struct platform_device *pdev)
+{
+	const struct bcm2835_aux_serial_driver_data *bcm_data;
+	struct uart_8250_port up = { };
+	struct bcm2835aux_data *data;
+	resource_size_t offset = 0;
+	struct resource *res;
+	unsigned int uartclk;
+	int ret;
+
+	/* allocate the custom structure */
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* initialize data */
+	up.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
+	up.port.dev = &pdev->dev;
+	up.port.regshift = 2;
+	up.port.type = PORT_16550;
+	up.port.iotype = UPIO_MEM;
+	up.port.fifosize = 8;
+	up.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE |
+			UPF_SKIP_TEST | UPF_IOREMAP;
+	up.port.rs485_config = serial8250_em485_config;
+	up.port.rs485_supported = serial8250_em485_supported;
+	up.rs485_start_tx = bcm2835aux_rs485_start_tx;
+	up.rs485_stop_tx = bcm2835aux_rs485_stop_tx;
+
+	/* initialize cached copy with power-on reset value */
+	data->cntl = BCM2835_AUX_UART_CNTL_RXEN | BCM2835_AUX_UART_CNTL_TXEN;
+
+	platform_set_drvdata(pdev, data);
+
+	/* get the clock - this also enables the HW */
+	data->clk = devm_clk_get_optional(&pdev->dev, NULL);
+	if (IS_ERR(data->clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->clk), "could not get clk\n");
+
+	/* get the interrupt */
+	ret = platform_get_irq(pdev, 0);
+	if (ret < 0)
+		return ret;
+	up.port.irq = ret;
+
+	/* map the main registers */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "memory resource not found");
+		return -EINVAL;
+	}
+
+	bcm_data = device_get_match_data(&pdev->dev);
+
+	/* Some UEFI implementations (e.g. tianocore/edk2 for the Raspberry Pi)
+	 * describe the miniuart with a base address that encompasses the auxiliary
+	 * registers shared between the miniuart and spi.
+	 *
+	 * This is due to historical reasons, see discussion here :
+	 * https://edk2.groups.io/g/devel/topic/87501357#84349
+	 *
+	 * We need to add the offset between the miniuart and auxiliary
+	 * registers to get the real miniuart base address.
+	 */
+	if (bcm_data)
+		offset = bcm_data->offset;
+
+	up.port.mapbase = res->start + offset;
+	up.port.mapsize = resource_size(res) - offset;
+
+	/* Check for a fixed line number */
+	ret = of_alias_get_id(pdev->dev.of_node, "serial");
+	if (ret >= 0)
+		up.port.line = ret;
+
+	/* enable the clock as a last step */
+	ret = clk_prepare_enable(data->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable uart clock - %d\n",
+			ret);
+		return ret;
+	}
+
+	uartclk = clk_get_rate(data->clk);
+	if (!uartclk) {
+		ret = device_property_read_u32(&pdev->dev, "clock-frequency", &uartclk);
+		if (ret) {
+			dev_err_probe(&pdev->dev, ret, "could not get clk rate\n");
+			goto dis_clk;
+		}
+	}
+
+	/* the HW-clock divider for bcm2835aux is 8,
+	 * but 8250 expects a divider of 16,
+	 * so we have to multiply the actual clock by 2
+	 * to get identical baudrates.
+	 */
+	up.port.uartclk = uartclk * 2;
+
+	/* register the port */
+	ret = serial8250_register_8250_port(&up);
+	if (ret < 0) {
+		dev_err_probe(&pdev->dev, ret, "unable to register 8250 port\n");
+		goto dis_clk;
+	}
+	data->line = ret;
+
+	return 0;
+
+dis_clk:
+	clk_disable_unprepare(data->clk);
+	return ret;
+}
+
+static int bcm2835aux_serial_remove(struct platform_device *pdev)
+{
+	struct bcm2835aux_data *data = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(data->line);
+	clk_disable_unprepare(data->clk);
+
+	return 0;
+}
+
+static const struct bcm2835_aux_serial_driver_data bcm2835_acpi_data = {
+	.offset = 0x40,
+};
+
+static const struct of_device_id bcm2835aux_serial_match[] = {
+	{ .compatible = "brcm,bcm2835-aux-uart" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match);
+
+static const struct acpi_device_id bcm2835aux_serial_acpi_match[] = {
+	{ "BCM2836", (kernel_ulong_t)&bcm2835_acpi_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, bcm2835aux_serial_acpi_match);
+
+static struct platform_driver bcm2835aux_serial_driver = {
+	.driver = {
+		.name = "bcm2835-aux-uart",
+		.of_match_table = bcm2835aux_serial_match,
+		.acpi_match_table = bcm2835aux_serial_acpi_match,
+	},
+	.probe  = bcm2835aux_serial_probe,
+	.remove = bcm2835aux_serial_remove,
+};
+module_platform_driver(bcm2835aux_serial_driver);
+
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+
+static int __init early_bcm2835aux_setup(struct earlycon_device *device,
+					const char *options)
+{
+	if (!device->port.membase)
+		return -ENODEV;
+
+	device->port.iotype = UPIO_MEM32;
+	device->port.regshift = 2;
+
+	return early_serial8250_setup(device, NULL);
+}
+
+OF_EARLYCON_DECLARE(bcm2835aux, "brcm,bcm2835-aux-uart",
+		    early_bcm2835aux_setup);
+#endif
+
+MODULE_DESCRIPTION("BCM2835 auxiliar UART driver");
+MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
+MODULE_LICENSE("GPL v2");