serial: sh: Use the clock framework to obtain clock config

Since we now have clock driver on the RCar Gen3 , obtain the clock
configuration using the clock framework functions. In case this
fails, fall back to the original code for pulling the clock config
directly out of OF.
Signed-off-by: NMarek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Signed-off-by: NNobuhiro Iwamatsu <iwamatsu@nigauri.org>

drivers/serial/serial_sh.c

@@ -9,6 +9,7 @@
 
 #include <common.h>
 #include <errno.h>
+#include <clk.h>
 #include <dm.h>
 #include <asm/io.h>
 #include <asm/processor.h>
@@ -214,15 +215,23 @@ static const struct udevice_id sh_serial_id[] ={
 static int sh_serial_ofdata_to_platdata(struct udevice *dev)
 {
 	struct sh_serial_platdata *plat = dev_get_platdata(dev);
+	struct clk sh_serial_clk;
 	fdt_addr_t addr;
+	int ret;
 
 	addr = fdtdec_get_addr(gd->fdt_blob, dev_of_offset(dev), "reg");
 	if (addr == FDT_ADDR_T_NONE)
 		return -EINVAL;
 
 	plat->base = addr;
-	plat->clk = fdtdec_get_int(gd->fdt_blob, dev_of_offset(dev), "clock",
-				   1);
+
+	ret = clk_get_by_name(dev, "fck", &sh_serial_clk);
+	if (!ret)
+		plat->clk = clk_get_rate(&sh_serial_clk);
+	else
+		plat->clk = fdtdec_get_int(gd->fdt_blob, dev_of_offset(dev),
+					   "clock", 1);
+
 	plat->type = dev_get_driver_data(dev);
 	return 0;
 }