Implement direct pineview backlight control.

drivers/gpu/drm/i915/i915_backlight.c

+/*
+ *  i915_backlight.c - ChromeOS specific backlight support for pineview
+ *
+ *
+ *  Copyright (C) 2010 ChromeOS contributors
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/backlight.h>
+
+#include "drmP.h"
+#include "i915_drm.h"
+#include "i915_drv.h"
+
+/*
+ * Somewhat arbitrarily choose a max brightness level of 256 (as full "on")
+ * and a PWM frequency of 0x1000.  The frequency can be as high as 0x7fff,
+ * but we do not need that level of flexibility.
+ */
+#define MAX_BRIGHTNESS 256
+#define PWM_FREQUENCY 0x1000
+
+/*
+ * The Pineview LVDS Backlight PWM Control register is a 32 bit word split
+ * into two unsigned 16 bit words: the high order short is the cycle frequency,
+ * and the low order word is the duty cycle.  According to i915_opregion.c,
+ * the low order bit of each short is unused.
+ *
+ * While the frequency is hardcoded, these macros provide masking and shifting
+ * for the duty cycle.
+ */
+#define CTL_TO_PWM(ctl) ((ctl & BACKLIGHT_DUTY_CYCLE_MASK) >> 1)
+#define PWM_TO_CTL(pwm) ((pwm << 1) & BACKLIGHT_DUTY_CYCLE_MASK)
+
+static int i915_get_intensity(struct backlight_device *bd)
+{
+        struct drm_device *dev = bl_get_data(bd);
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        u32 blc_pwm_ctl;
+        int level, pwm_val;
+
+        blc_pwm_ctl = I915_READ(BLC_PWM_CTL);
+        pwm_val = CTL_TO_PWM(blc_pwm_ctl);
+        level = (pwm_val * MAX_BRIGHTNESS) / PWM_FREQUENCY;
+
+        return level;
+}
+
+static int i915_set_intensity(struct backlight_device *bd)
+{
+        struct drm_device *dev = bl_get_data(bd);
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        int level, pwm_val;
+        u32 blc_pwm_ctl;
+
+        level = bd->props.brightness;
+        if (level > MAX_BRIGHTNESS)
+                level = MAX_BRIGHTNESS;
+
+        pwm_val = (level * PWM_FREQUENCY) / MAX_BRIGHTNESS;
+        blc_pwm_ctl = (PWM_FREQUENCY << BACKLIGHT_MODULATION_FREQ_SHIFT) |
+                PWM_TO_CTL(pwm_val);
+        I915_WRITE(BLC_PWM_CTL, blc_pwm_ctl);
+
+        return 0;
+}
+
+static struct backlight_ops i915_bl_ops = {
+        .get_brightness = i915_get_intensity,
+        .update_status = i915_set_intensity,
+};
+
+void i915_backlight_init(struct drm_device *dev)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        struct backlight_device *bd;
+
+        if (!IS_PINEVIEW(dev)) {
+                dev_printk(KERN_WARNING, &dev->pdev->dev,
+                "i915_backlight_init only supports the pineview version\n");
+                return;
+        }
+
+        bd = backlight_device_register("i915_backlight",
+                &dev->pdev->dev, dev, &i915_bl_ops);
+        if (IS_ERR(bd)) {
+                dev_printk(KERN_WARNING, &dev->pdev->dev,
+                        "Unable to register i915 backlight.\n");
+                return;
+        }
+
+        dev_priv->backlight = bd;
+        bd->props.max_brightness = MAX_BRIGHTNESS;
+        bd->props.brightness = 0;
+        backlight_update_status(bd);
+        return;
+}
+
+void i915_backlight_exit(struct drm_device *dev)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        if (dev_priv->backlight) {
+                backlight_device_unregister(dev_priv->backlight);
+                dev_priv->backlight = NULL;
+        }
+}