[PATCH V3 4/6] tty: serial: meson: The UART baud rate calculation is described using the common clock code. Also added S4 chip uart Compatible.

[Yu Tu <yu.tu@amlogic.com>]

Using the common Clock code to describe the UART baud rate clock makes
it easier for the UART driver to be compatible with the baud rate
requirements of the UART IP on different meson chips

Signed-off-by: Yu Tu <yu.tu@amlogic.com>
---
 drivers/tty/serial/Kconfig      |   1 +
 drivers/tty/serial/meson_uart.c | 311 ++++++++++++++++++++++++++------
 2 files changed, 257 insertions(+), 55 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 780908d43557..32e238173036 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -198,6 +198,7 @@ config SERIAL_KGDB_NMI
 config SERIAL_MESON
 	tristate "Meson serial port support"
 	depends on ARCH_MESON
+	depends on COMMON_CLK
 	select SERIAL_CORE
 	help
 	  This enables the driver for the on-chip UARTs of the Amlogic
diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 99efe62a1507..07eb1f40aaaa 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/clk-provider.h>
 #include <linux/console.h>
 #include <linux/delay.h>
 #include <linux/init.h>
@@ -65,9 +66,7 @@
 #define AML_UART_RECV_IRQ(c)		((c) & 0xff)
 
 /* AML_UART_REG5 bits */
-#define AML_UART_BAUD_MASK		0x7fffff
 #define AML_UART_BAUD_USE		BIT(23)
-#define AML_UART_BAUD_XTAL		BIT(24)
 
 #define AML_UART_PORT_NUM		12
 #define AML_UART_PORT_OFFSET		6
@@ -76,6 +75,21 @@
 #define AML_UART_POLL_USEC		5
 #define AML_UART_TIMEOUT_USEC		10000
 
+struct meson_uart_data {
+	struct uart_port	port;
+	struct clk		*pclk;
+	struct clk		*baud_clk;
+	struct clk_divider	baud_div;
+	struct clk_mux		use_xtal_mux;
+	struct clk_mux		xtal_clk_sel_mux;
+	struct clk_mux		xtal2_clk_sel_mux;
+	struct clk_fixed_factor	xtal_div2;
+	struct clk_fixed_factor	xtal_div3;
+	struct clk_fixed_factor	clk81_div4;
+	bool			no_clk81_input;
+	bool			has_xtal_clk_sel;
+};
+
 static struct uart_driver meson_uart_driver;
 
 static struct uart_port *meson_ports[AML_UART_PORT_NUM];
@@ -270,14 +284,11 @@ static void meson_uart_reset(struct uart_port *port)
 static int meson_uart_startup(struct uart_port *port)
 {
 	u32 val;
-	int ret = 0;
+	int ret;
 
-	val = readl(port->membase + AML_UART_CONTROL);
-	val |= AML_UART_CLEAR_ERR;
-	writel(val, port->membase + AML_UART_CONTROL);
-	val &= ~AML_UART_CLEAR_ERR;
-	writel(val, port->membase + AML_UART_CONTROL);
+	meson_uart_reset(port);
 
+	val = readl(port->membase + AML_UART_CONTROL);
 	val |= (AML_UART_RX_EN | AML_UART_TX_EN);
 	writel(val, port->membase + AML_UART_CONTROL);
 
@@ -295,19 +306,17 @@ static int meson_uart_startup(struct uart_port *port)
 
 static void meson_uart_change_speed(struct uart_port *port, unsigned long baud)
 {
+	struct meson_uart_data *private_data = port->private_data;
 	u32 val;
 
 	while (!meson_uart_tx_empty(port))
 		cpu_relax();
 
-	if (port->uartclk == 24000000) {
-		val = ((port->uartclk / 3) / baud) - 1;
-		val |= AML_UART_BAUD_XTAL;
-	} else {
-		val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1;
-	}
+	val = readl(port->membase + AML_UART_REG5);
 	val |= AML_UART_BAUD_USE;
 	writel(val, port->membase + AML_UART_REG5);
+
+	clk_set_rate(private_data->baud_clk, baud);
 }
 
 static void meson_uart_set_termios(struct uart_port *port,
@@ -397,11 +406,27 @@ static int meson_uart_verify_port(struct uart_port *port,
 
 static void meson_uart_release_port(struct uart_port *port)
 {
-	/* nothing to do */
+	struct meson_uart_data *private_data = port->private_data;
+
+	clk_disable_unprepare(private_data->baud_clk);
+	clk_disable_unprepare(private_data->pclk);
 }
 
 static int meson_uart_request_port(struct uart_port *port)
 {
+	struct meson_uart_data *private_data = port->private_data;
+	int ret;
+
+	ret = clk_prepare_enable(private_data->pclk);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(private_data->baud_clk);
+	if (ret) {
+		clk_disable_unprepare(private_data->pclk);
+		return ret;
+	}
+
 	return 0;
 }
 
@@ -629,56 +654,175 @@ static struct uart_driver meson_uart_driver = {
 	.cons		= MESON_SERIAL_CONSOLE,
 };
 
-static inline struct clk *meson_uart_probe_clock(struct device *dev,
-						 const char *id)
+static int meson_uart_register_clk(struct uart_port *port,
+				   const char *name_suffix,
+				   const struct clk_parent_data *parent_data,
+				   unsigned int num_parents,
+				   const struct clk_ops *ops,
+				   struct clk_hw *hw)
 {
-	struct clk *clk = NULL;
+	struct clk_init_data init = { };
+	char clk_name[32];
 	int ret;
 
-	clk = devm_clk_get(dev, id);
-	if (IS_ERR(clk))
-		return clk;
+	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
+		 name_suffix);
 
-	ret = clk_prepare_enable(clk);
-	if (ret) {
-		dev_err(dev, "couldn't enable clk\n");
-		return ERR_PTR(ret);
-	}
+	init.name = clk_name;
+	init.ops = ops;
+	init.flags = CLK_SET_RATE_PARENT;
+	init.parent_data = parent_data;
+	init.num_parents = num_parents;
+
+	hw->init = &init;
 
-	devm_add_action_or_reset(dev,
-			(void(*)(void *))clk_disable_unprepare,
-			clk);
+	ret = devm_clk_hw_register(port->dev, hw);
+	if (ret)
+		return dev_err_probe(port->dev, ret,
+				     "Failed to register the '%s' clock\n",
+				     clk_name);
 
-	return clk;
+	return ret;
 }
 
-static int meson_uart_probe_clocks(struct platform_device *pdev,
-				   struct uart_port *port)
-{
-	struct clk *clk_xtal = NULL;
-	struct clk *clk_pclk = NULL;
-	struct clk *clk_baud = NULL;
+static int meson_uart_probe_clocks(struct uart_port *port,
+				   bool register_clk81_div4)
+{
+	struct meson_uart_data *private_data = port->private_data;
+	struct clk_parent_data use_xtal_mux_parents[2] = {
+		{ .index = -1, },
+		{ .index = -1, },
+	};
+	struct clk_parent_data xtal_clk_sel_mux_parents[2] = { };
+	struct clk_parent_data xtal2_clk_sel_mux_parents[2] = { };
+	struct clk_parent_data xtal_div_parent = { .fw_name = "xtal", };
+	struct clk_parent_data clk81_div_parent = { .fw_name = "baud", };
+	struct clk_parent_data baud_div_parent = { };
+	struct clk *clk_baud, *clk_xtal;
+	int ret;
 
-	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
-	if (IS_ERR(clk_pclk))
-		return PTR_ERR(clk_pclk);
+	private_data->pclk = devm_clk_get(port->dev, "pclk");
+	if (IS_ERR(private_data->pclk))
+		return dev_err_probe(port->dev, PTR_ERR(private_data->pclk),
+				     "Failed to get the 'pclk' clock\n");
+
+	clk_baud = devm_clk_get(port->dev, "baud");
+	if (IS_ERR(clk_baud))
+		return dev_err_probe(port->dev, PTR_ERR(clk_baud),
+				     "Failed to get the 'baud' clock\n");
 
-	clk_xtal = meson_uart_probe_clock(&pdev->dev, "xtal");
+	clk_xtal = devm_clk_get(port->dev, "xtal");
 	if (IS_ERR(clk_xtal))
-		return PTR_ERR(clk_xtal);
+		return dev_err_probe(port->dev, PTR_ERR(clk_xtal),
+				     "Failed to get the 'xtal' clock\n");
+
+	private_data->xtal_div3.mult = 1;
+	private_data->xtal_div3.div = 3;
+	ret = meson_uart_register_clk(port, "xtal_div3", &xtal_div_parent,
+				      1, &clk_fixed_factor_ops,
+				      &private_data->xtal_div3.hw);
+	if (ret)
+		return ret;
 
-	clk_baud = meson_uart_probe_clock(&pdev->dev, "baud");
-	if (IS_ERR(clk_baud))
-		return PTR_ERR(clk_baud);
+	if (register_clk81_div4) {
+		private_data->clk81_div4.mult = 1;
+		private_data->clk81_div4.div = 4;
+		ret = meson_uart_register_clk(port, "clk81_div4",
+					      &clk81_div_parent, 1,
+					      &clk_fixed_factor_ops,
+					      &private_data->clk81_div4.hw);
+		if (ret)
+			return ret;
+
+		use_xtal_mux_parents[0].hw = &private_data->clk81_div4.hw;
+	}
 
-	port->uartclk = clk_get_rate(clk_baud);
+	if (private_data->has_xtal_clk_sel) {
+		private_data->xtal_div2.mult = 1;
+		private_data->xtal_div2.div = 2;
+		ret = meson_uart_register_clk(port, "xtal_div2",
+					      &xtal_div_parent, 1,
+					      &clk_fixed_factor_ops,
+					      &private_data->xtal_div2.hw);
+		if (ret)
+			return ret;
+
+		xtal_clk_sel_mux_parents[0].hw = &private_data->xtal_div3.hw;
+		xtal_clk_sel_mux_parents[1].fw_name = "xtal";
+
+		private_data->xtal_clk_sel_mux.reg = port->membase + AML_UART_REG5;
+		private_data->xtal_clk_sel_mux.mask = 0x1;
+		private_data->xtal_clk_sel_mux.shift = 26;
+		private_data->xtal_clk_sel_mux.flags = CLK_MUX_ROUND_CLOSEST;
+		ret = meson_uart_register_clk(port, "xtal_clk_sel",
+					      xtal_clk_sel_mux_parents,
+					      ARRAY_SIZE(xtal_clk_sel_mux_parents),
+					      &clk_mux_ops,
+					      &private_data->xtal_clk_sel_mux.hw);
+		if (ret)
+			return ret;
+
+		xtal2_clk_sel_mux_parents[0].hw = &private_data->xtal_clk_sel_mux.hw;
+		xtal2_clk_sel_mux_parents[1].hw = &private_data->xtal_div2.hw;
+
+		private_data->xtal2_clk_sel_mux.reg = port->membase + AML_UART_REG5;
+		private_data->xtal2_clk_sel_mux.mask = 0x1;
+		private_data->xtal2_clk_sel_mux.shift = 27;
+		private_data->xtal2_clk_sel_mux.flags = CLK_MUX_ROUND_CLOSEST;
+		ret = meson_uart_register_clk(port, "xtal2_clk_sel",
+					      xtal2_clk_sel_mux_parents,
+					      ARRAY_SIZE(xtal2_clk_sel_mux_parents),
+					      &clk_mux_ops,
+					      &private_data->xtal2_clk_sel_mux.hw);
+		if (ret)
+			return ret;
+
+		use_xtal_mux_parents[1].hw = &private_data->xtal2_clk_sel_mux.hw;
+	} else {
+		use_xtal_mux_parents[1].hw = &private_data->xtal_div3.hw;
+	}
+
+	private_data->use_xtal_mux.reg = port->membase + AML_UART_REG5;
+	private_data->use_xtal_mux.mask = 0x1;
+	private_data->use_xtal_mux.shift = 24;
+	private_data->use_xtal_mux.flags = CLK_MUX_ROUND_CLOSEST;
+	ret = meson_uart_register_clk(port, "use_xtal", use_xtal_mux_parents,
+				      ARRAY_SIZE(use_xtal_mux_parents),
+				      &clk_mux_ops,
+				      &private_data->use_xtal_mux.hw);
+	if (ret)
+		return ret;
+
+	baud_div_parent.hw = &private_data->use_xtal_mux.hw;
+
+	private_data->baud_div.reg = port->membase + AML_UART_REG5;
+	private_data->baud_div.shift = 0;
+	private_data->baud_div.width = 23;
+	private_data->baud_div.flags = CLK_DIVIDER_ROUND_CLOSEST;
+	ret = meson_uart_register_clk(port, "baud_div",
+				      &baud_div_parent, 1,
+				      &clk_divider_ops,
+				      &private_data->baud_div.hw);
+	if (ret)
+		return ret;
+
+	private_data->baud_clk = devm_clk_hw_get_clk(port->dev,
+						     &private_data->baud_div.hw,
+						     "baud_rate");
+	if (IS_ERR(private_data->baud_clk))
+		return dev_err_probe(port->dev,
+				     PTR_ERR(private_data->baud_clk),
+				     "Failed to request the 'baud_rate' clock\n");
 
 	return 0;
 }
 
 static int meson_uart_probe(struct platform_device *pdev)
 {
+	struct meson_uart_data *private_data;
 	struct resource *res_mem, *res_irq;
+	struct clk *clk_baud, *clk_xtal;
+	bool register_clk81_div4;
 	struct uart_port *port;
 	int ret = 0;
 	int id = -1;
@@ -711,18 +855,37 @@ static int meson_uart_probe(struct platform_device *pdev)
 		return -EBUSY;
 	}
 
-	port = devm_kzalloc(&pdev->dev, sizeof(struct uart_port), GFP_KERNEL);
-	if (!port)
+	private_data = devm_kzalloc(&pdev->dev, sizeof(*private_data),
+				    GFP_KERNEL);
+	if (!private_data)
 		return -ENOMEM;
 
+	if (device_get_match_data(&pdev->dev))
+		private_data->has_xtal_clk_sel = true;
+
+	private_data->pclk = devm_clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(private_data->pclk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(private_data->pclk),
+				     "Failed to get the 'pclk' clock\n");
+
+	clk_baud = devm_clk_get(&pdev->dev, "baud");
+	if (IS_ERR(clk_baud))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk_baud),
+				     "Failed to get the 'baud' clock\n");
+
+	clk_xtal = devm_clk_get(&pdev->dev, "xtal");
+	if (IS_ERR(clk_xtal))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk_xtal),
+				     "Failed to get the 'xtal' clock\n");
+
+	register_clk81_div4 = clk_get_rate(clk_xtal) != clk_get_rate(clk_baud);
+
+	port = &private_data->port;
+
 	port->membase = devm_ioremap_resource(&pdev->dev, res_mem);
 	if (IS_ERR(port->membase))
 		return PTR_ERR(port->membase);
 
-	ret = meson_uart_probe_clocks(pdev, port);
-	if (ret)
-		return ret;
-
 	port->iotype = UPIO_MEM;
 	port->mapbase = res_mem->start;
 	port->mapsize = resource_size(res_mem);
@@ -735,6 +898,12 @@ static int meson_uart_probe(struct platform_device *pdev)
 	port->x_char = 0;
 	port->ops = &meson_uart_ops;
 	port->fifosize = 64;
+	port->uartclk = clk_get_rate(clk_baud);
+	port->private_data = private_data;
+
+	ret = meson_uart_probe_clocks(port, register_clk81_div4);
+	if (ret)
+		return ret;
 
 	meson_ports[pdev->id] = port;
 	platform_set_drvdata(pdev, port);
@@ -761,10 +930,42 @@ static int meson_uart_remove(struct platform_device *pdev)
 }
 
 static const struct of_device_id meson_uart_dt_match[] = {
-	{ .compatible = "amlogic,meson6-uart" },
-	{ .compatible = "amlogic,meson8-uart" },
-	{ .compatible = "amlogic,meson8b-uart" },
-	{ .compatible = "amlogic,meson-gx-uart" },
+	{
+		.compatible = "amlogic,meson6-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson8-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson8b-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson-gxbb-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson-gxl-uart",
+		.data = (void *)true,
+	},
+	{
+		.compatible = "amlogic,meson-g12a-uart",
+		.data = (void *)true,
+	},
+	{
+		.compatible = "amlogic,meson-s4-uart",
+		.data = (void *)true,
+	},
+	/*
+	 * deprecated, don't use anymore because it doesn't differentiate
+	 * between GXBB and GXL which have different revisions of the UART IP.
+	 */
+	{
+		.compatible = "amlogic,meson-gx-uart",
+		.data = (void *)false,
+	},
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, meson_uart_dt_match);
-- 
2.33.1