This patch adds a framebuffer notifier in order to detect

FB_BLANK events and switch the JBT6K74 LCM controller into
its power saving mode.

This has the potential of saving something like 50mW during screen blank.

Signed-off-by: Harald Welte <laforge@openmoko.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/drivers/video/display/jbt6k74.c b/drivers/video/display/jbt6k74.c
index b40629839fc..9570543fc3d 100644
--- a/drivers/video/display/jbt6k74.c
+++ b/drivers/video/display/jbt6k74.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2006-2007 by Openmoko, Inc.
  * Author: Harald Welte <laforge@openmoko.org>,
  * 	   Stefan Schmidt <stefan@openmoko.org>
+ * Copyright (C) 2008 by Harald Welte <laforge@openmoko.org>
  * All rights reserved.
  *
  * This program is free software; you can redistribute it and/or
@@ -21,6 +22,7 @@
  * MA 02111-1307 USA
  *
  */
+
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/module.h>
@@ -28,6 +30,7 @@
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 #include <linux/jbt6k74.h>
+#include <linux/fb.h>
 
 enum jbt_register {
 	JBT_REG_SLEEP_IN		= 0x10,
@@ -111,6 +114,7 @@ struct jbt_info {
 	enum jbt_state state, last_state;
 	struct spi_device *spi_dev;
 	struct mutex lock;		/* protects tx_buf and reg_cache */
+	struct notifier_block fb_notif;
 	u16 tx_buf[8];
 	u16 reg_cache[0xEE];
 	int have_resumed;
@@ -548,6 +552,40 @@ static struct attribute_group jbt_attr_group = {
 	.attrs	= jbt_sysfs_entries,
 };
 
+static int fb_notifier_callback(struct notifier_block *self,
+				unsigned long event, void *data)
+{
+	struct jbt_info *jbt;
+	struct fb_event *evdata = data;
+	int fb_blank;
+
+	if (event != FB_EVENT_BLANK && event != FB_EVENT_CONBLANK)
+		return 0;
+
+	fb_blank = *(int *)evdata->data;
+	jbt = container_of(self, struct jbt_info, fb_notif);
+
+	switch (fb_blank) {
+	case FB_BLANK_UNBLANK:
+	case FB_BLANK_NORMAL:
+		jbt6k74_enter_state(jbt, JBT_STATE_NORMAL);
+		jbt6k74_display_onoff(jbt, 1);
+		break;
+	case FB_BLANK_VSYNC_SUSPEND:
+	case FB_BLANK_HSYNC_SUSPEND:
+		/* FIXME: we disable SLEEP since it would result in
+		 * a visible artefact (white screen) before the backlight
+		 * is dimmed to a dark enough level */
+		/* jbt6k74_enter_state(jbt, JBT_STATE_SLEEP); */
+		break;
+	case FB_BLANK_POWERDOWN:
+		jbt6k74_enter_state(jbt, JBT_STATE_DEEP_STANDBY);
+		break;
+	}
+
+	return 0;
+}
+
 /* linux device model infrastructure */
 
 static int __devinit jbt_probe(struct spi_device *spi)
@@ -595,8 +633,17 @@ static int __devinit jbt_probe(struct spi_device *spi)
 		goto err_off;
 	}
 
+	jbt->fb_notif.notifier_call = fb_notifier_callback;
+	rc = fb_register_client(&jbt->fb_notif);
+	if (rc < 0) {
+		dev_err(&spi->dev, "cannot register notifier\n");
+		goto err_sysfs;
+	}
+
 	return 0;
 
+err_sysfs:
+	sysfs_remove_group(&spi->dev.kobj, &jbt_attr_group);
 err_off:
 	jbt6k74_display_onoff(jbt, 0);
 err_standby:
@@ -615,6 +662,7 @@ static int __devexit jbt_remove(struct spi_device *spi)
 	/* We don't want to switch off the display in case the user
 	 * accidentially onloads the module (whose use count normally is 0) */
 
+	fb_unregister_client(&jbt->fb_notif);
 	sysfs_remove_group(&spi->dev.kobj, &jbt_attr_group);
 	dev_set_drvdata(&spi->dev, NULL);
 	kfree(jbt);