serial: sh-sci: Drop the interface clock

As no platform defines an interface clock the SCI driver always falls
back to a clock named "peripheral_clk".
  - On SH platforms that clock is the base clock for the SCI functional
    clock and has the same frequency,
  - On ARM platforms that clock doesn't exist, and clk_get() will return
    the default clock for the device.
We can thus make the functional clock mandatory and drop the interface
clock.

EPROBE_DEFER is handled for clocks that may be referenced from DT (i.e.
"fck", and the deprecated "sci_ick").

Cc: devicetree@vger.kernel.org
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
[geert: Handle EPROBE_DEFER, reformat description, break long comment line]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 41 insertions, 23 deletions

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 960e50a97558..cc6fa55231ba 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -92,8 +92,6 @@ struct sci_port {
         struct timer_list       break_timer;
         int                     break_flag;
 
-        /* Interface clock */
-        struct clk              *iclk;
         /* Function clock */
         struct clk              *fclk;
 
@@ -457,9 +455,8 @@ static void sci_port_enable(struct sci_port *sci_port)
 
         pm_runtime_get_sync(sci_port->port.dev);
 
-        clk_prepare_enable(sci_port->iclk);
-        sci_port->port.uartclk = clk_get_rate(sci_port->iclk);
         clk_prepare_enable(sci_port->fclk);
+        sci_port->port.uartclk = clk_get_rate(sci_port->fclk);
 }
 
 static void sci_port_disable(struct sci_port *sci_port)
@@ -476,7 +473,6 @@ static void sci_port_disable(struct sci_port *sci_port)
         sci_port->break_flag = 0;
 
         clk_disable_unprepare(sci_port->fclk);
-        clk_disable_unprepare(sci_port->iclk);
 
         pm_runtime_put_sync(sci_port->port.dev);
 }
@@ -1622,7 +1618,7 @@ static int sci_notifier(struct notifier_block *self,
                 struct uart_port *port = &sci_port->port;
 
                 spin_lock_irqsave(&port->lock, flags);
-                port->uartclk = clk_get_rate(sci_port->iclk);
+                port->uartclk = clk_get_rate(sci_port->fclk);
                 spin_unlock_irqrestore(&port->lock, flags);
         }
 
@@ -2241,6 +2237,42 @@ static struct uart_ops sci_uart_ops = {
 #endif
 };
 
+static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
+{
+        /* Get the SCI functional clock. It's called "fck" on ARM. */
+        sci_port->fclk = clk_get(dev, "fck");
+        if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER)
+                return -EPROBE_DEFER;
+        if (!IS_ERR(sci_port->fclk))
+                return 0;
+
+        /*
+         * But it used to be called "sci_ick", and we need to maintain DT
+         * backward compatibility.
+         */
+        sci_port->fclk = clk_get(dev, "sci_ick");
+        if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER)
+                return -EPROBE_DEFER;
+        if (!IS_ERR(sci_port->fclk))
+                return 0;
+
+        /* SH has historically named the clock "sci_fck". */
+        sci_port->fclk = clk_get(dev, "sci_fck");
+        if (!IS_ERR(sci_port->fclk))
+                return 0;
+
+        /*
+         * Not all SH platforms declare a clock lookup entry for SCI devices,
+         * in which case we need to get the global "peripheral_clk" clock.
+         */
+        sci_port->fclk = clk_get(dev, "peripheral_clk");
+        if (!IS_ERR(sci_port->fclk))
+                return 0;
+
+        dev_err(dev, "failed to get functional clock\n");
+        return PTR_ERR(sci_port->fclk);
+}
+
 static int sci_init_single(struct platform_device *dev,
                            struct sci_port *sci_port, unsigned int index,
                            struct plat_sci_port *p, bool early)
@@ -2333,22 +2365,9 @@ static int sci_init_single(struct platform_device *dev,
                 sci_port->sampling_rate = p->sampling_rate;
 
         if (!early) {
-                sci_port->iclk = clk_get(&dev->dev, "sci_ick");
-                if (IS_ERR(sci_port->iclk)) {
-                        sci_port->iclk = clk_get(&dev->dev, "peripheral_clk");
-                        if (IS_ERR(sci_port->iclk)) {
-                                dev_err(&dev->dev, "can't get iclk\n");
-                                return PTR_ERR(sci_port->iclk);
-                        }
-                }
-
-                /*
-                 * The function clock is optional, ignore it if we can't
-                 * find it.
-                 */
-                sci_port->fclk = clk_get(&dev->dev, "sci_fck");
-                if (IS_ERR(sci_port->fclk))
-                        sci_port->fclk = NULL;
+                ret = sci_init_clocks(sci_port, &dev->dev);
+                if (ret < 0)
+                        return ret;
 
                 port->dev = &dev->dev;
 
@@ -2405,7 +2424,6 @@ static int sci_init_single(struct platform_device *dev,
 
 static void sci_cleanup_single(struct sci_port *port)
 {
-        clk_put(port->iclk);
         clk_put(port->fclk);
 
         pm_runtime_disable(port->port.dev);