i2c-pxa: prepare clock before use

On OLPC XO-1.75 (MMP2), a WARN_ON() was occurring during boot
since the clock being enabled by i2c-pxa had not been prepared.

Use clk_prepare_enable() to ensure that the prepare operation
has taken place, and use clk_disable_unprepare() in the matching
shutdown paths.
Signed-off-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-pxa.c

@@ -1160,7 +1160,7 @@ static int i2c_pxa_probe(struct platform_device *dev)
 		i2c->adap.class = plat->class;
 	}
 
-	clk_enable(i2c->clk);
+	clk_prepare_enable(i2c->clk);
 
 	if (i2c->use_pio) {
 		i2c->adap.algo = &i2c_pxa_pio_algorithm;
@@ -1202,7 +1202,7 @@ static int i2c_pxa_probe(struct platform_device *dev)
 	if (!i2c->use_pio)
 		free_irq(irq, i2c);
 ereqirq:
-	clk_disable(i2c->clk);
+	clk_disable_unprepare(i2c->clk);
 	iounmap(i2c->reg_base);
 eremap:
 	clk_put(i2c->clk);
@@ -1221,7 +1221,7 @@ static int i2c_pxa_remove(struct platform_device *dev)
 	if (!i2c->use_pio)
 		free_irq(i2c->irq, i2c);
 
-	clk_disable(i2c->clk);
+	clk_disable_unprepare(i2c->clk);
 	clk_put(i2c->clk);
 
 	iounmap(i2c->reg_base);