serial: 8250_dw: add support for clk api

This commit implements support for using the clk api; this lets us use
the "clocks" property with device tree, instead of having to use
clock-frequency.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 24 insertions, 9 deletions

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index db0e66f6dd0e..3dedd2470db1 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -26,6 +26,7 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
+#include <linux/clk.h>
 
 #include "8250.h"
 
@@ -55,8 +56,9 @@
 
 
 struct dw8250_data {
-        int     last_lcr;
-        int     line;
+        int             last_lcr;
+        int             line;
+        struct clk      *clk;
 };
 
 static void dw8250_serial_out(struct uart_port *p, int offset, int value)
@@ -136,8 +138,13 @@ static int dw8250_probe_of(struct uart_port *p)
         if (!of_property_read_u32(np, "reg-shift", &val))
                 p->regshift = val;
 
+        /* clock got configured through clk api, all done */
+        if (p->uartclk)
+                return 0;
+
+        /* try to find out clock frequency from DT as fallback */
         if (of_property_read_u32(np, "clock-frequency", &val)) {
-                dev_err(p->dev, "no clock-frequency property set\n");
+                dev_err(p->dev, "clk or clock-frequency not defined\n");
                 return -EINVAL;
         }
         p->uartclk = val;
@@ -294,9 +301,20 @@ static int dw8250_probe(struct platform_device *pdev)
         if (!uart.port.membase)
                 return -ENOMEM;
 
+        data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        data->clk = devm_clk_get(&pdev->dev, NULL);
+        if (!IS_ERR(data->clk)) {
+                clk_prepare_enable(data->clk);
+                uart.port.uartclk = clk_get_rate(data->clk);
+        }
+
         uart.port.iotype = UPIO_MEM;
         uart.port.serial_in = dw8250_serial_in;
         uart.port.serial_out = dw8250_serial_out;
+        uart.port.private_data = data;
 
         dw8250_setup_port(&uart);
 
@@ -312,12 +330,6 @@ static int dw8250_probe(struct platform_device *pdev)
                 return -ENODEV;
         }
 
-        data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
-        if (!data)
-                return -ENOMEM;
-
-        uart.port.private_data = data;
-
         data->line = serial8250_register_8250_port(&uart);
         if (data->line < 0)
                 return data->line;
@@ -333,6 +345,9 @@ static int dw8250_remove(struct platform_device *pdev)
 
         serial8250_unregister_port(data->line);
 
+        if (!IS_ERR(data->clk))
+                clk_disable_unprepare(data->clk);
+
         return 0;
 }