[PATCH V4 3/5] tty: serial: meson: The UART baud rate

[Yu Tu]

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@xxxxxxxxxxx>
---
 drivers/tty/serial/meson_uart.c | 224 +++++++++++++++++++++++---------
 1 file changed, 163 insertions(+), 61 deletions(-)

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 7570958d010c..1004fd0b0c9e 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 +75,13 @@
 #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;
+	bool			use_xtal_clk;
+};
+
 static struct uart_driver meson_uart_driver;
 
 static struct uart_port *meson_ports[AML_UART_PORT_NUM];
@@ -268,14 +274,11 @@ 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);
 
@@ -293,19 +296,17 @@ 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,
@@ -395,11 +396,27 @@ 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;
 }
 
@@ -629,55 +646,105 @@ 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)
+#define CLK_NAME(name) \
+({\
+	char clk_name[32];\
+	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev), #name);\
+	clk_name;\
+})
+
+static struct clk_div_table xtal_div_table[] = {
+	{ 0, 3  },
+	{ 1, 1  },
+	{ 2, 2  },
+	{ 3, 2  },
+};
+
+static int meson_uart_probe_clocks(struct uart_port *port)
 {
-	struct clk *clk = NULL;
-	int ret;
+	struct meson_uart_data *private_data = port->private_data;
+	struct clk *clk_baud, *clk_xtal;
+	struct clk_hw *hw;
+	struct clk_parent_data use_xtal_mux_parents[2] = {
+		{ .index = -1, },
+		{ .index = -1, },
+	};
 
-	clk = devm_clk_get(dev, id);
-	if (IS_ERR(clk))
-		return clk;
+	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");
 
-	ret = clk_prepare_enable(clk);
-	if (ret) {
-		dev_err(dev, "couldn't enable clk\n");
-		return ERR_PTR(ret);
+	clk_baud = devm_clk_get(port->dev, "baud");
+	if (IS_ERR(clk_baud)) {
+		dev_err(port->dev, "Failed to get the 'baud' clock\n");
+		return PTR_ERR(clk_baud);
 	}
 
-	devm_add_action_or_reset(dev,
-			(void(*)(void *))clk_disable_unprepare,
-			clk);
-
-	return clk;
-}
-
-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;
-
-	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
-	if (IS_ERR(clk_pclk))
-		return PTR_ERR(clk_pclk);
-
-	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);
-
-	clk_baud = meson_uart_probe_clock(&pdev->dev, "baud");
-	if (IS_ERR(clk_baud))
-		return PTR_ERR(clk_baud);
+		return dev_err_probe(port->dev, PTR_ERR(clk_xtal),
+				     "Failed to get the 'xtal' clock\n");
+
+	if (private_data->use_xtal_clk) {
+		hw = devm_clk_hw_register_divider_table(port->dev,
+							CLK_NAME(xtal_div),
+							__clk_get_name(clk_baud),
+							CLK_SET_RATE_NO_REPARENT,
+							port->membase + AML_UART_REG5,
+							26, 2,
+							CLK_DIVIDER_READ_ONLY,
+							xtal_div_table, NULL);
+		if (IS_ERR(hw))
+			return PTR_ERR(hw);
+
+		use_xtal_mux_parents[1].hw = hw;
+	} else {
+		hw = devm_clk_hw_register_fixed_factor(port->dev,
+						       CLK_NAME(clk81_div4),
+						       __clk_get_name(clk_baud),
+						       CLK_SET_RATE_NO_REPARENT,
+						       1, 4);
+		if (IS_ERR(hw))
+			return PTR_ERR(hw);
+
+		use_xtal_mux_parents[0].hw = hw;
+	}
 
-	port->uartclk = clk_get_rate(clk_baud);
+	hw = __devm_clk_hw_register_mux(port->dev, NULL,
+					CLK_NAME(use_xtal),
+					ARRAY_SIZE(use_xtal_mux_parents),
+					NULL, NULL,
+					use_xtal_mux_parents,
+					CLK_SET_RATE_PARENT,
+					port->membase + AML_UART_REG5,
+					24, 0x1,
+					CLK_MUX_READ_ONLY,
+					NULL, NULL);
+	if (IS_ERR(hw))
+		return PTR_ERR(hw);
+
+	port->uartclk = clk_hw_get_rate(hw);
+
+	hw = devm_clk_hw_register_divider(port->dev,
+					  CLK_NAME(baud_div),
+					  clk_hw_get_name(hw),
+					  CLK_SET_RATE_PARENT,
+					  port->membase + AML_UART_REG5,
+					  0, 23,
+					  CLK_DIVIDER_ROUND_CLOSEST,
+					  NULL);
+	if (IS_ERR(hw))
+		return PTR_ERR(hw);
+
+	private_data->baud_clk = clk_hw_get_clk(hw, "baud_rate");
 
 	return 0;
 }
 
 static int meson_uart_probe(struct platform_device *pdev)
 {
+	struct meson_uart_data *private_data;
 	struct resource *res_mem;
 	struct uart_port *port;
 	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
@@ -716,18 +783,20 @@ 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->use_xtal_clk = true;
+
+	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);
@@ -740,7 +809,11 @@ static int meson_uart_probe(struct platform_device *pdev)
 	port->x_char = 0;
 	port->ops = &meson_uart_ops;
 	port->fifosize = fifosize;
+	port->private_data = private_data;
 
+	ret = meson_uart_probe_clocks(port);
+	if (ret)
+		return ret;
 	meson_ports[pdev->id] = port;
 	platform_set_drvdata(pdev, port);
 
@@ -766,10 +839,39 @@ 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,
+	},
+	/*
+	 * deprecated, don't use anymore because it doesn't differentiate
+	 * between GXBB, GXL and G12A 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