[PATCH v3 0/2] Add the property to make backlight OCP level selectable

[PATCH v3 0/2] Add the property to make backlight OCP level selectable

[cy_huang]

From: ChiYuan Huang <cy_huang@richtek.com>

This patch series is to add the backlight ocp level property parsing.

Since  v3
- Refine the description for backlight ocp property.
- Use the enum to list the supported value.

Since v2
- change the property name from the register style 'richtek,bled-ocp-cel' to
  'richtek,bled-ocp-microamp'.
- Use the clamp and roundup to get the ovp level selector.

ChiYuan Huang (2):
  dt-bindings: backlight: rt4831: Add the new ocp level property
  backlight: rt4831: Apply ocp level from devicetree

 .../leds/backlight/richtek,rt4831-backlight.yaml   |  5 ++++
 drivers/video/backlight/rt4831-backlight.c         | 33 +++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

-- 
2.7.4

[PATCH v3 1/2] dt-bindings: backlight: rt4831: Add the new ocp level property

[cy_huang]

From: ChiYuan Huang <cy_huang@richtek.com>

Add 'richtek,bled-ocp-microamp' property to make it chooseable.

The wrong backlight ocp level may affect the backlight channel output
current smaller than configured.

Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
---
Since v3:
- Refine the description for backlight ocp property.
- Use the enum to list the supported value.

Since v2:
- Change the property name from 'richtek,bled-ocp-sel' to 'richtek,bled-ocp-microamp'.

---
 .../devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
index e0ac686..99e9e13 100644
--- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
+++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
@@ -47,6 +47,11 @@ properties:
     minimum: 0
     maximum: 3
 
+  richtek,bled-ocp-microamp:
+    description: |
+      Backlight over current protection level.
+    enum: [900000, 1200000, 1500000, 1800000]
+
   richtek,channel-use:
     description: |
       Backlight LED channel to be used.
-- 
2.7.4

[PATCH v3 2/2] backlight: rt4831: Apply ocp level from devicetree

[cy_huang]

From: ChiYuan Huang <cy_huang@richtek.com>

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>
---
Since v2:
- Prase the 'richtek,bled-ocp-microamp', clamp the value in min/max range, and
  roundup to get the best selector.

---
 drivers/video/backlight/rt4831-backlight.c | 33 +++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/rt4831-backlight.c b/drivers/video/backlight/rt4831-backlight.c
index 42155c7..8c2001b 100644
--- 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 = roundup(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");
-- 
2.7.4

Re: [PATCH v3 1/2] dt-bindings: backlight: rt4831: Add the new ocp level property

[Daniel Thompson]

On Thu, Jun 09, 2022 at 10:22:18AM +0800, cy_huang wrote:
> From: ChiYuan Huang <cy_huang@richtek.com>
> 
> Add 'richtek,bled-ocp-microamp' property to make it chooseable.
> 
> The wrong backlight ocp level may affect the backlight channel output
> current smaller than configured.
> 
> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH v3 1/2] dt-bindings: backlight: rt4831: Add the new ocp level property

[Krzysztof Kozlowski]

On 09/06/2022 04:22, cy_huang wrote:
> From: ChiYuan Huang <cy_huang@richtek.com>
> 
> Add 'richtek,bled-ocp-microamp' property to make it chooseable.
> 
> The wrong backlight ocp level may affect the backlight channel output
> current smaller than configured.
> 
> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> ---
> Since v3:
> - Refine the description for backlight ocp property.
> - Use the enum to list the supported value.
> 
> Since v2:
> - Change the property name from 'richtek,bled-ocp-sel' to 'richtek,bled-ocp-microamp'.
> 


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof