[PATCH] powerpc: More via-pmu backlight fixes

The via-pmu backlight code (introduced in 2.6.18) has various design issues
causing crashes on machines using it like the old Wallstreet powerbook
(Michael, the author, never managed to test on these and I just got my hand
on one of those old beasts).

This fixes them by no longer trying to hijack the backlight device of the
frontmost framebuffer (causing that framebuffer to crash) but having it's
own local bits instead. Might look weird but it's better that way on those
old machines, at least as a last-minute fix for 2.6.18. We might rework
the whole thing later. This patch also changes the way it gets notified of
sleep and wakeup in order to properly shut the backlight down on sleep and
bring it back on wakeup.

Signed-off-by: Benjamin Herrenschmidt <[e-mail]>
Cc: "Antonino A. Daplas" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/macintosh/via-pmu-backlight.c

···
 static struct backlight_properties pmu_backlight_data;
 static spinlock_t pmu_backlight_lock;
 static int sleeping;
+static u8 bl_curve[FB_BACKLIGHT_LEVELS];
 
-static int pmu_backlight_get_level_brightness(struct fb_info *info,
-		int level)
+static void pmu_backlight_init_curve(u8 off, u8 min, u8 max)
+{
+	unsigned int i, flat, count, range = (max - min);
+
+	bl_curve[0] = off;
+
+	for (flat = 1; flat < (FB_BACKLIGHT_LEVELS / 16); ++flat)
+		bl_curve[flat] = min;
+
+	count = FB_BACKLIGHT_LEVELS * 15 / 16;
+	for (i = 0; i < count; ++i)
+		bl_curve[flat + i] = min + (range * (i + 1) / count);
+}
+
+static int pmu_backlight_curve_lookup(int value)
+{
+	int level = (FB_BACKLIGHT_LEVELS - 1);
+	int i, max = 0;
+
+	/* Look for biggest value */
+	for (i = 0; i < FB_BACKLIGHT_LEVELS; i++)
+		max = max((int)bl_curve[i], max);
+
+	/* Look for nearest value */
+	for (i = 0; i < FB_BACKLIGHT_LEVELS; i++) {
+		int diff = abs(bl_curve[i] - value);
+		if (diff < max) {
+			max = diff;
+			level = i;
+		}
+	}
+	return level;
+}
+
+static int pmu_backlight_get_level_brightness(int level)
 {
 	int pmulevel;
 
 	/* Get and convert the value */
-	mutex_lock(&info->bl_mutex);
-	pmulevel = info->bl_curve[level] * FB_BACKLIGHT_MAX / MAX_PMU_LEVEL;
-	mutex_unlock(&info->bl_mutex);
-
+	pmulevel = bl_curve[level] * FB_BACKLIGHT_MAX / MAX_PMU_LEVEL;
 	if (pmulevel < 0)
 		pmulevel = 0;
 	else if (pmulevel > MAX_PMU_LEVEL)
···
 
 static int pmu_backlight_update_status(struct backlight_device *bd)
 {
-	struct fb_info *info = class_get_devdata(&bd->class_dev);
 	struct adb_request req;
 	unsigned long flags;
 	int level = bd->props->brightness;
···
 		level = 0;
 
 	if (level > 0) {
-		int pmulevel = pmu_backlight_get_level_brightness(info, level);
+		int pmulevel = pmu_backlight_get_level_brightness(level);
 
 		pmu_request(&req, NULL, 2, PMU_BACKLIGHT_BRIGHT, pmulevel);
 		pmu_wait_complete(&req);
···
 };
 
 #ifdef CONFIG_PM
-static int pmu_backlight_sleep_call(struct pmu_sleep_notifier *self, int when)
+void pmu_backlight_set_sleep(int sleep)
 {
 	unsigned long flags;
 
 	spin_lock_irqsave(&pmu_backlight_lock, flags);
-
-	switch (when) {
-	case PBOOK_SLEEP_REQUEST:
-		sleeping = 1;
-		break;
-	case PBOOK_WAKE:
-		sleeping = 0;
-		break;
-	}
-
+	sleeping = sleep;
 	spin_unlock_irqrestore(&pmu_backlight_lock, flags);
-
-	return PBOOK_SLEEP_OK;
 }
-
-static struct pmu_sleep_notifier pmu_backlight_sleep_notif = {
-	.notifier_call = pmu_backlight_sleep_call,
-};
-#endif
+#endif /* CONFIG_PM */
 
 void __init pmu_backlight_init()
 {
 	struct backlight_device *bd;
-	struct fb_info *info;
 	char name[10];
 	int level, autosave;
 
···
 	    !machine_is_compatible("PowerBook1,1"))
 		return;
 
-	/* Actually, this is a hack, but I don't know of a better way
-	 * to get the first framebuffer device.
-	 */
-	info = registered_fb[0];
-	if (!info) {
-		printk("pmubl: No framebuffer found\n");
-		goto error;
-	}
+	snprintf(name, sizeof(name), "pmubl");
 
-	snprintf(name, sizeof(name), "pmubl%d", info->node);
-
-	bd = backlight_device_register(name, info, &pmu_backlight_data);
+	bd = backlight_device_register(name, NULL, &pmu_backlight_data);
 	if (IS_ERR(bd)) {
 		printk("pmubl: Backlight registration failed\n");
 		goto error;
 	}
-
-	mutex_lock(&info->bl_mutex);
-	info->bl_dev = bd;
-	fb_bl_default_curve(info, 0x7F, 0x46, 0x0E);
-	mutex_unlock(&info->bl_mutex);
+	pmu_backlight_init_curve(0x7F, 0x46, 0x0E);
 
 	level = pmu_backlight_data.max_brightness;
 
···
 		pmu_request(&req, NULL, 2, 0xd9, 0);
 		pmu_wait_complete(&req);
 
-		mutex_lock(&info->bl_mutex);
-		level = pmac_backlight_curve_lookup(info,
+		level = pmu_backlight_curve_lookup(
 				(req.reply[0] >> 4) *
 				pmu_backlight_data.max_brightness / 15);
-		mutex_unlock(&info->bl_mutex);
 	}
 
 	up(&bd->sem);
···
 	if (!pmac_backlight)
 		pmac_backlight = bd;
 	mutex_unlock(&pmac_backlight_mutex);
-
-#ifdef CONFIG_PM
-	pmu_register_sleep_notifier(&pmu_backlight_sleep_notif);
-#endif
 
 	printk("pmubl: Backlight initialized (%s)\n", name);
 

drivers/macintosh/via-pmu.c

···
 	out_8(&via[IER], IER_SET | SR_INT | CB1_INT);
 }
 
+extern void pmu_backlight_set_sleep(int sleep);
+
 static int
 pmac_suspend_devices(void)
 {
···
 		printk(KERN_ERR "Driver sleep failed\n");
 		return -EBUSY;
 	}
+
+#ifdef CONFIG_PMAC_BACKLIGHT
+	/* Tell backlight code not to muck around with the chip anymore */
+	pmu_backlight_set_sleep(1);
+#endif
 
 	/* Call platform functions marked "on sleep" */
 	pmac_pfunc_i2c_suspend();
···
 pmac_wakeup_devices(void)
 {
 	mdelay(100);
+
+#ifdef CONFIG_PMAC_BACKLIGHT
+	/* Tell backlight code it can use the chip again */
+	pmu_backlight_set_sleep(0);
+#endif
 
 	/* Power back up system devices (including the PIC) */
 	device_power_up();