Input: omap4-keypad - react on keypresses if device is runtime-suspended

According to SWPU235AB, table 26-6, fclk is required to generate events
at least on OMAP4460, so keep fclk enabled all the time the device
is opened.

Suggested-by: Tony Lindgren <[e-mail]>
Signed-off-by: Andreas Kemnade <[e-mail]>
Reviewed-by: Tony Lindgren <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/keyboard/omap4-keypad.c

···
 #include <linux/module.h>
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
+#include <linux/clk.h>
 #include <linux/errno.h>
 #include <linux/io.h>
 #include <linux/of.h>
···
 	bool no_autorepeat;
 	u64 keys;
 	unsigned short *keymap;
+	struct clk *fck;
 };
 
 static int kbd_readl(struct omap4_keypad *keypad_data, u32 offset)
···
 	if (error)
 		return error;
 
+	error = clk_prepare_enable(keypad_data->fck);
+	if (error)
+		goto out;
+
 	disable_irq(keypad_data->irq);
 
 	kbd_writel(keypad_data, OMAP4_KBD_CTRL,
···
 
 	enable_irq(keypad_data->irq);
 
+out:
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 
-	return 0;
+	return error;
 }
 
 static void omap4_keypad_stop(struct omap4_keypad *keypad_data)
···
 	disable_irq(keypad_data->irq);
 	omap4_keypad_stop(keypad_data);
 	enable_irq(keypad_data->irq);
+	clk_disable_unprepare(keypad_data->fck);
 
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
···
 	}
 
 	keypad_data->irq = irq;
+	keypad_data->fck = devm_clk_get(&pdev->dev, "fck");
+	if (IS_ERR(keypad_data->fck))
+		return dev_err_probe(&pdev->dev, PTR_ERR(keypad_data->fck),
+				     "unable to get fck");
+
 	mutex_init(&keypad_data->lock);
 	platform_set_drvdata(pdev, keypad_data);