[PATCH 2/2] tty: serial: 8250: Add MediaTek BTIF controller on MT7622 and MT7623 SoC

[sean.wang]

From: Sean Wang <sean.wang@xxxxxxxxxxxx>

MediaTek BTIF controller is the serial interface similar to UART but it
works only as the digital device which is mainly used to communicate with
the connectivity module also called CONNSYS inside the SoC which could be
mostly found on those MediaTek SoCs with Bluetooth feature.

And the controller is made as being compatible with the 8250 register
layout so it tends to be integrated with existing 8250 core driver and
have no requirement for the modem configuration additionally such as the
baud rate calculation and assignment.

Signed-off-by: Sean Wang <sean.wang@xxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_btif.c | 224 ++++++++++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig     |   9 ++
 drivers/tty/serial/8250/Makefile    |   1 +
 3 files changed, 234 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_btif.c

diff --git a/drivers/tty/serial/8250/8250_btif.c b/drivers/tty/serial/8250/8250_btif.c
new file mode 100644
index 0000000..06433e9
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_btif.c
@@ -0,0 +1,224 @@
+/*
+ * Driver for MediaTek BTIF Controller
+ *
+ * Copyright (C) 2017 Sean Wang <sean.wang@xxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_reg.h>
+
+#include "8250.h"
+
+#define MTK_BTIF_TRI_LVL	0x60
+#define BTIF_LOOP		BIT(7)
+
+struct mtk_btif_data {
+	int			line;
+	struct clk		*main_clk;
+};
+
+static void
+mtk_btif_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
+{
+	if (!state)
+		pm_runtime_get_sync(port->dev);
+
+	serial8250_do_pm(port, state, old);
+
+	if (state)
+		pm_runtime_put_sync_suspend(port->dev);
+}
+
+static int mtk_btif_probe_of(struct platform_device *pdev, struct uart_port *p,
+			     struct mtk_btif_data *data)
+{
+	int err;
+
+	data->main_clk = devm_clk_get(&pdev->dev, "main");
+	if (IS_ERR(data->main_clk)) {
+		dev_warn(&pdev->dev, "Can't get main clock\n");
+		return PTR_ERR(data->main_clk);
+	}
+
+	err = clk_prepare_enable(data->main_clk);
+	if (err) {
+		dev_warn(&pdev->dev, "Can't prepare main_clk\n");
+		clk_put(data->main_clk);
+		return err;
+	}
+
+	p->uartclk = clk_get_rate(data->main_clk);
+
+	return 0;
+}
+
+static int mtk_btif_runtime_suspend(struct device *dev)
+{
+	struct mtk_btif_data *data = dev_get_drvdata(dev);
+
+	clk_disable_unprepare(data->main_clk);
+
+	return 0;
+}
+
+static int mtk_btif_runtime_resume(struct device *dev)
+{
+	struct mtk_btif_data *data = dev_get_drvdata(dev);
+	int err;
+
+	err = clk_prepare_enable(data->main_clk);
+	if (err) {
+		dev_warn(dev, "Can't enable main clock\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int mtk_btif_probe(struct platform_device *pdev)
+{
+	struct uart_8250_port uart = {};
+	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	struct mtk_btif_data *data;
+	int err;
+	u32 tmp;
+
+	if (!regs || !irq) {
+		dev_err(&pdev->dev, "no registers/irq defined\n");
+		return -EINVAL;
+	}
+
+	uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
+					 resource_size(regs));
+	if (!uart.port.membase)
+		return -ENOMEM;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (pdev->dev.of_node) {
+		err = mtk_btif_probe_of(pdev, &uart.port, data);
+		if (err)
+			return err;
+	} else {
+		return -ENODEV;
+	}
+
+	spin_lock_init(&uart.port.lock);
+	uart.port.mapbase = regs->start;
+	uart.port.irq = irq->start;
+	uart.port.pm = mtk_btif_do_pm;
+	uart.port.type = PORT_8250;
+	uart.port.flags = UPF_FIXED_TYPE;
+	uart.port.dev = &pdev->dev;
+	uart.port.iotype = UPIO_MEM32;
+	uart.port.regshift = 2;
+	uart.port.private_data = data;
+
+	platform_set_drvdata(pdev, data);
+
+	pm_runtime_enable(&pdev->dev);
+
+	if (!pm_runtime_enabled(&pdev->dev)) {
+		err = mtk_btif_runtime_resume(&pdev->dev);
+		if (err)
+			return err;
+	}
+
+	if (of_property_read_bool(pdev->dev.of_node, "mediatek,loopback")) {
+		dev_info(&pdev->dev, "btif is entering loopback mode\n");
+		tmp = readl(uart.port.membase + MTK_BTIF_TRI_LVL);
+		tmp |= BTIF_LOOP;
+		writel(tmp, uart.port.membase + MTK_BTIF_TRI_LVL);
+	}
+
+	data->line = serial8250_register_8250_port(&uart);
+	if (data->line < 0)
+		return data->line;
+
+	return 0;
+}
+
+static int mtk_btif_remove(struct platform_device *pdev)
+{
+	struct mtk_btif_data *data = platform_get_drvdata(pdev);
+
+	pm_runtime_get_sync(&pdev->dev);
+
+	serial8250_unregister_port(data->line);
+
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
+
+	if (!pm_runtime_status_suspended(&pdev->dev))
+		mtk_btif_runtime_suspend(&pdev->dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int mtk_btif_suspend(struct device *dev)
+{
+	struct mtk_btif_data *data = dev_get_drvdata(dev);
+
+	serial8250_suspend_port(data->line);
+
+	return 0;
+}
+
+static int mtk_btif_resume(struct device *dev)
+{
+	struct mtk_btif_data *data = dev_get_drvdata(dev);
+
+	serial8250_resume_port(data->line);
+
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+static const struct dev_pm_ops mtk_btif_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(mtk_btif_suspend, mtk_btif_resume)
+	SET_RUNTIME_PM_OPS(mtk_btif_runtime_suspend, mtk_btif_runtime_resume,
+			   NULL)
+};
+
+static const struct of_device_id mtk_btif_of_match[] = {
+	{ .compatible = "mediatek,mt7622-btif" },
+	{ .compatible = "mediatek,mt7623-btif" },
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mtk_btif_of_match);
+
+static struct platform_driver mtk_btif_platform_driver = {
+	.driver = {
+		.name		= "mediatek-btif",
+		.pm		= &mtk_btif_pm_ops,
+		.of_match_table	= mtk_btif_of_match,
+	},
+	.probe			= mtk_btif_probe,
+	.remove			= mtk_btif_remove,
+};
+module_platform_driver(mtk_btif_platform_driver);
+
+MODULE_AUTHOR("Sean Wang <sean.wang@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MediaTek BTIF controller driver");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index a1161ec..0e18cfc 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -403,6 +403,15 @@ config SERIAL_8250_MT6577
 	  If you have a Mediatek based board and want to use the
 	  serial port, say Y to this option. If unsure, say N.
 
+config SERIAL_8250_BTIF
+	tristate "MediaTek BTIF controller support"
+	depends on SERIAL_8250 && ARCH_MEDIATEK
+	help
+	  Selecting this option will enable BTIF controller used by MediaTek
+	  Bluetooth to communicate with internal hardware module inside the
+	  SoC also being called CONNSYS which could be found on MediaTek SoCs
+	  with Bluetooth feature, say Y to this option. If unsure, say N.
+
 config SERIAL_8250_UNIPHIER
 	tristate "Support for UniPhier on-chip UART"
 	depends on SERIAL_8250
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index a44a99a..2fc73ce 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o
 obj-$(CONFIG_SERIAL_8250_OMAP)		+= 8250_omap.o
 obj-$(CONFIG_SERIAL_8250_LPC18XX)	+= 8250_lpc18xx.o
 obj-$(CONFIG_SERIAL_8250_MT6577)	+= 8250_mtk.o
+obj-$(CONFIG_SERIAL_8250_BTIF)		+= 8250_btif.o
 obj-$(CONFIG_SERIAL_8250_UNIPHIER)	+= 8250_uniphier.o
 obj-$(CONFIG_SERIAL_8250_INGENIC)	+= 8250_ingenic.o
 obj-$(CONFIG_SERIAL_8250_LPSS)		+= 8250_lpss.o
-- 
2.7.4