backlight: rt4831: Apply ocp level from devicetree

Add 'richtek,bled-ocp-microamp' property parsing in
device_property_init function.

This value may configure prior to the kernel driver. If it's not specified in
devicetree, keep the original setting. Else, use clamp to align the
value in min/max range and also roundup to choose the best selector.

Reported-by: Lucas Tsai <lucas_tsai@richtek.com>
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/1655807788-24511-3-git-send-email-u0084500@gmail.com

diff --git a/drivers/video/backlight/rt4831-backlight.c b/drivers/video/backlight/rt4831-backlight.c
index 42155c7..eb8c59e 100644 (file)
--- a/drivers/video/backlight/rt4831-backlight.c
+++ b/drivers/video/backlight/rt4831-backlight.c
@@ -12,6 +12,7 @@
 #define RT4831_REG_BLCFG       0x02
 #define RT4831_REG_BLDIML      0x04
 #define RT4831_REG_ENABLE      0x08
+#define RT4831_REG_BLOPT2      0x11
 
 #define RT4831_BLMAX_BRIGHTNESS        2048
 
@@ -23,6 +24,11 @@
 #define RT4831_BLDIML_MASK     GENMASK(2, 0)
 #define RT4831_BLDIMH_MASK     GENMASK(10, 3)
 #define RT4831_BLDIMH_SHIFT    3
+#define RT4831_BLOCP_MASK      GENMASK(1, 0)
+
+#define RT4831_BLOCP_MINUA     900000
+#define RT4831_BLOCP_MAXUA     1800000
+#define RT4831_BLOCP_STEPUA    300000
 
 struct rt4831_priv {
        struct device *dev;
@@ -85,7 +91,7 @@ static int rt4831_parse_backlight_properties(struct rt4831_priv *priv,
 {
        struct device *dev = priv->dev;
        u8 propval;
-       u32 brightness;
+       u32 brightness, ocp_uA;
        unsigned int val = 0;
        int ret;
 
@@ -120,6 +126,31 @@ static int rt4831_parse_backlight_properties(struct rt4831_priv *priv,
        if (ret)
                return ret;
 
+       /*
+        * This OCP level is used to protect and limit the inductor current.
+        * If inductor peak current reach the level, low-side MOSFET will be
+        * turned off. Meanwhile, the output channel current may be limited.
+        * To match the configured channel current, the inductor chosen must
+        * be higher than the OCP level.
+        *
+        * Not like the OVP level, the default 21V can be used in the most
+        * application. But if the chosen OCP level is smaller than needed,
+        * it will also affect the backlight channel output current to be
+        * smaller than the register setting.
+        */
+       ret = device_property_read_u32(dev, "richtek,bled-ocp-microamp",
+                                      &ocp_uA);
+       if (!ret) {
+               ocp_uA = clamp_val(ocp_uA, RT4831_BLOCP_MINUA,
+                                  RT4831_BLOCP_MAXUA);
+               val = DIV_ROUND_UP(ocp_uA - RT4831_BLOCP_MINUA,
+                                  RT4831_BLOCP_STEPUA);
+               ret = regmap_update_bits(priv->regmap, RT4831_REG_BLOPT2,
+                                        RT4831_BLOCP_MASK, val);
+               if (ret)
+                       return ret;
+       }
+
        ret = device_property_read_u8(dev, "richtek,channel-use", &propval);
        if (ret) {
                dev_err(dev, "richtek,channel-use DT property missing\n");