[RFC] cpm_uart: Add generic clock API support to set baudrates

[Laurent Pinchart <laurentp@cse-semaphore.com>]

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This patch introduces baudrate setting support via the generic clock API.
When present the optional device tree clock property is used instead of
fsl-cpm-brg. Platforms can then define complex clock schemes, to output
the serial clock on an external pin for instance.

This is required to support RS485 ports on a platform I'm working on (TBox
CPU32 - see http://www.cse-semaphore.com/products/t-box/t-box-ms.php).

---
 drivers/serial/cpm_uart/cpm_uart.h      |    1 +
 drivers/serial/cpm_uart/cpm_uart_core.c |   26 +++++++++++++++++++-------
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/serial/cpm_uart/cpm_uart.h b/drivers/serial/cpm_uart/cpm_uart.h
index d0c55e2..2e64c03 100644
--- a/drivers/serial/cpm_uart/cpm_uart.h
+++ b/drivers/serial/cpm_uart/cpm_uart.h
@@ -77,6 +77,7 @@ struct uart_cpm_port {
 	unsigned char		*rx_buf;
 	u32			flags;
 	void			(*set_lineif)(struct uart_cpm_port *);
+	struct clk		*clk;
 	u8			brg;
 	uint			 dp_addr;
 	void 			*mem_addr;
diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c b/drivers/serial/cpm_uart/cpm_uart_core.c
index d3c19e5..438e460 100644
--- a/drivers/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/serial/cpm_uart/cpm_uart_core.c
@@ -44,6 +44,7 @@
 #include <linux/fs_uart_pd.h>
 #include <linux/gpio.h>
 #include <linux/of_gpio.h>
+#include <linux/clk.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -641,7 +642,10 @@ static void cpm_uart_set_termios(struct uart_port *port,
 		out_be16(&sccp->scc_psmr, (sbits << 12) | scval);
 	}
 
-	cpm_set_brg(pinfo->brg - 1, baud);
+	if (pinfo->clk)
+		clk_set_rate(pinfo->clk, baud);
+	else
+		cpm_set_brg(pinfo->brg - 1, baud);
 	spin_unlock_irqrestore(&port->lock, flags);
 }
 
@@ -991,13 +995,21 @@ static int cpm_uart_init_port(struct device_node *np,
 	int ret;
 	int i;
 
-	data = of_get_property(np, "fsl,cpm-brg", &len);
-	if (!data || len != 4) {
-		printk(KERN_ERR "CPM UART %s has no/invalid "
-		                "fsl,cpm-brg property.\n", np->name);
-		return -EINVAL;
+	data = of_get_property(np, "clock", NULL);
+	if (data) {
+		struct clk *clk = clk_get(NULL, (const char*)data);
+		if (!IS_ERR(clk))
+			pinfo->clk = clk;
+	}
+	if (!pinfo->clk) {
+		data = of_get_property(np, "fsl,cpm-brg", &len);
+		if (!data || len != 4) {
+			printk(KERN_ERR "CPM UART %s has no/invalid "
+			                "fsl,cpm-brg property.\n", np->name);
+			return -EINVAL;
+		}
+		pinfo->brg = *data;
 	}
-	pinfo->brg = *data;
 
 	data = of_get_property(np, "fsl,cpm-command", &len);
 	if (!data || len != 4) {
-- 
1.5.0


-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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