video: mdss: Color temperature interface using PCC

 * MDSS5 supports Polynomial Color Correction. Use this to implement
   a simple sysfs API for adjusting RGB scaling values. This can be
   used to implement color temperature and other controls.
 * Why use this when we have KCAL? This code is dead simple, the
   interface is in the right place, and it allows for 128X accuracy.

Change-Id: Icc497dafff7d25560f0e4e9597d52c78d5ab9178

drivers/video/msm/mdss/mdss_fb.c

@@ -499,6 +499,68 @@ static ssize_t mdss_fb_get_doze_mode(struct device *dev,
 	return scnprintf(buf, PAGE_SIZE, "%d\n", mfd->doze_mode);
 }
 
+static int pcc_r = 32768, pcc_g = 32768, pcc_b = 32768;
+static ssize_t mdss_get_rgb(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d %d %d\n", pcc_r, pcc_g, pcc_b);
+}
+
+/**
+ * simple color temperature interface using polynomial color correction
+ *
+ * input values are r/g/b adjustments from 0-32768 representing 0 -> 1
+ *
+ * example adjustment @ 3500K:
+ * 1.0000 / 0.5515 / 0.2520 = 32768 / 25828 / 17347
+ *
+ * reference chart:
+ * http://www.vendian.org/mncharity/dir3/blackbody/UnstableURLs/bbr_color.html
+ */
+static ssize_t mdss_set_rgb(struct device *dev,
+							struct device_attribute *attr,
+							const char *buf, size_t count)
+{
+	uint32_t r = 0, g = 0, b = 0;
+	struct mdp_pcc_cfg_data pcc_cfg;
+	u32 copyback = 0;
+
+    if (count > 19)
+		return -EINVAL;
+
+	sscanf(buf, "%d %d %d", &r, &g, &b);
+
+	if (r < 0 || r > 32768)
+		return -EINVAL;
+	if (g < 0 || g > 32768)
+		return -EINVAL;
+	if (b < 0 || b > 32768)
+		return -EINVAL;
+
+	pr_info("%s: r=%d g=%d b=%d", __func__, r, g, b);
+
+	memset(&pcc_cfg, 0, sizeof(struct mdp_pcc_cfg_data));
+
+	pcc_cfg.block = MDP_LOGICAL_BLOCK_DISP_0;
+	if (r == 32768 && g == 32768 && b == 32768)
+		pcc_cfg.ops = MDP_PP_OPS_DISABLE;
+	else
+		pcc_cfg.ops = MDP_PP_OPS_ENABLE;
+	pcc_cfg.ops |= MDP_PP_OPS_WRITE;
+	pcc_cfg.r.r = r;
+	pcc_cfg.g.g = g;
+	pcc_cfg.b.b = b;
+
+	if (mdss_mdp_pcc_config(&pcc_cfg, &copyback) == 0) {
+		pcc_r = r;
+		pcc_g = g;
+		pcc_b = b;
+		return count;
+	}
+
+	return -EINVAL;
+}
+
 static DEVICE_ATTR(msm_fb_type, S_IRUGO, mdss_fb_get_type, NULL);
 static DEVICE_ATTR(msm_fb_split, S_IRUGO | S_IWUSR, mdss_fb_show_split,
 					mdss_fb_store_split);
@@ -511,6 +573,7 @@ static DEVICE_ATTR(msm_fb_src_split_info, S_IRUGO, mdss_fb_get_src_split_info,
 	NULL);
 static DEVICE_ATTR(always_on, S_IRUGO | S_IWUSR | S_IWGRP,
 	mdss_fb_get_doze_mode, mdss_fb_set_doze_mode);
+static DEVICE_ATTR(rgb, S_IRUGO | S_IWUSR | S_IWGRP, mdss_get_rgb, mdss_set_rgb);
 
 static struct attribute *mdss_fb_attrs[] = {
 	&dev_attr_msm_fb_type.attr,
@@ -521,6 +584,7 @@ static struct attribute *mdss_fb_attrs[] = {
 	&dev_attr_msm_fb_panel_info.attr,
 	&dev_attr_msm_fb_src_split_info.attr,
 	&dev_attr_always_on.attr,
+	&dev_attr_rgb.attr,
 	NULL,
 };