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Message-ID: <20250612105712.GD381401@google.com>
Date: Thu, 12 Jun 2025 14:48:13 +0100
From: Lee Jones <lee@...nel.org>
To: Michal Vokáč <michal.vokac@...ft.com>
Cc: Pavel Machek <pavel@...nel.org>,
Christian Marangi <ansuelsmth@...il.com>,
linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [RFC RESEND] leds: lp55xx: led-cur property is not properly
applied to multi-led
On Fri, 23 May 2025, Michal Vokáč wrote:
> Hi,
>
> I am trying to wrap my head around the implementation of the multicolor
> LED support in the lp55xx family drivers.
>
> The situation is quite straight forward when each LED is registered
> and controlled individually but it gets quite messy once you use
> the multi-color LED binding.
>
> I am working with the imx6dl-yapp43-pegasus.dts board (in-tree). There
> is one RGB LED driven by a LP5562 LED controller. Currently the RGB LED
> is modeled as three separate LEDs and each of the LEDs has
> individually tuned led-cur property. I would like to change the device
> tree and use the multi-led binding to be able to use triggers on a chosen
> RGB color.
>
> When I was experimenting with that, I realized there is something wrong
> with the colors and identified that the led-cur property is not properly
> applied in case the multi-led binding is used. What ultimately happens is
> that the led_current of the first LED in the multi-led group is set to
> the value of led-cur property of the last LED in the group.
> All the other LEDs in the group are left with the default reset value
> of the controller (0xaf in my case).
Does this help you:
https://lore.kernel.org/r/20250526-led-fix-v4-1-33345f6c4a78@axis.com
> Example:
>
> led-controller@30 {
> compatible = "ti,lp5562";
> reg = <0x30>;
> clock-mode = /bits/ 8 <1>;
> #address-cells = <1>;
> #size-cells = <0>;
> status = "disabled";
>
> multi-led@0 {
> #address-cells = <1>;
> #size-cells = <0>;
> color = <LED_COLOR_ID_RGB>;
> function = LED_FUNCTION_INDICATOR;
>
> led@0 {
> led-cur = /bits/ 8 <0x6e>;
> max-cur = /bits/ 8 <0xc8>;
> reg = <0>;
> color = <LED_COLOR_ID_RED>;
> };
>
> led@1 {
> led-cur = /bits/ 8 <0xbe>;
> max-cur = /bits/ 8 <0xc8>;
> reg = <1>;
> color = <LED_COLOR_ID_GREEN>;
> };
>
> led@2 {
> led-cur = /bits/ 8 <0xbe>;
> max-cur = /bits/ 8 <0xc8>;
> reg = <2>;
> color = <LED_COLOR_ID_BLUE>;
> };
> };
>
> Result (values read out directly with i2cget)
>
> led@0 current = 0xbe, should be 0x6e
> led@1 current = 0xaf, should be 0xbe
> led@2 current = 0xaf, should be 0xbe
>
> I tried to describe the steps that led to my discovery in the comments to
> the file. Unfortunately I could not really figure out how this could be
> properly fixed.
>
> I would appreciate any comments to this problem and hopefully some ideas
> how it could be solved.
>
> Thank you,
> Michal
> ---
> drivers/leds/leds-lp55xx-common.c | 34 +++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/drivers/leds/leds-lp55xx-common.c b/drivers/leds/leds-lp55xx-common.c
> index e71456a56ab8..d2fd2d296049 100644
> --- a/drivers/leds/leds-lp55xx-common.c
> +++ b/drivers/leds/leds-lp55xx-common.c
> @@ -1060,12 +1060,17 @@ static int lp55xx_register_leds(struct lp55xx_led *led, struct lp55xx_chip *chip
> return -EINVAL;
> }
>
> + // Step 8
> + // num_channels = 1
> for (i = 0; i < num_channels; i++) {
>
> /* do not initialize channels that are not connected */
> if (pdata->led_config[i].led_current == 0)
> continue;
>
> + // The pdata->led_config[0].led_current contains the led-cur
> + // property value of the last LED from the multi-led node.
> + // Here we store that value to the first LED in that node.
> led_current = pdata->led_config[i].led_current;
> each = led + i;
> ret = lp55xx_init_led(each, chip, i);
> @@ -1119,8 +1124,16 @@ static int lp55xx_parse_common_child(struct device_node *np,
> struct lp55xx_led_config *cfg,
> int led_number, int *chan_nr)
> {
> + // Step 6
> + // This is called 3-times (n-times in general, for each LED in the multi-led node)
> + // led_number = 0
> + // np = led@[0,1,2]
> int ret;
>
> + // Size of the cfg is "1 lp55xx_led_config"
> + // led_number = 0 for each of the n-calls
> + // So the name, led_current and max_current variables are being
> + // overwritten until values from the last led@ subnode are stored.
> of_property_read_string(np, "chan-name",
> &cfg[led_number].name);
> of_property_read_u8(np, "led-cur",
> @@ -1139,6 +1152,11 @@ static int lp55xx_parse_multi_led_child(struct device_node *child,
> struct lp55xx_led_config *cfg,
> int child_number, int color_number)
> {
> + // Step 5
> + // This is called 3-times (n-times in general, for each LED in the multi-led node)
> + // child_number = 0
> + // color_number = [0,1,2]
> + // child = led@[0,1,2]
> int chan_nr, color_id, ret;
>
> ret = lp55xx_parse_common_child(child, cfg, child_number, &chan_nr);
> @@ -1159,6 +1177,10 @@ static int lp55xx_parse_multi_led(struct device_node *np,
> struct lp55xx_led_config *cfg,
> int child_number)
> {
> + // Step 4
> + // This is called just once
> + // child_number = 0
> + // np = multi-led node
> int num_colors = 0, ret;
>
> for_each_available_child_of_node_scoped(np, child) {
> @@ -1169,6 +1191,7 @@ static int lp55xx_parse_multi_led(struct device_node *np,
> num_colors++;
> }
>
> + // num_colors = 3
> cfg[child_number].num_colors = num_colors;
>
> return 0;
> @@ -1178,6 +1201,10 @@ static int lp55xx_parse_logical_led(struct device_node *np,
> struct lp55xx_led_config *cfg,
> int child_number)
> {
> + // Step 3
> + // This is called just once
> + // child_number = 0
> + // np = multi-led node
> int led_color, ret;
> int chan_nr = 0;
>
> @@ -1189,6 +1216,7 @@ static int lp55xx_parse_logical_led(struct device_node *np,
> return ret;
>
> if (led_color == LED_COLOR_ID_RGB)
> + // We go this way
> return lp55xx_parse_multi_led(np, cfg, child_number);
>
> ret = lp55xx_parse_common_child(np, cfg, child_number, &chan_nr);
> @@ -1215,18 +1243,22 @@ static struct lp55xx_platform_data *lp55xx_of_populate_pdata(struct device *dev,
> if (!pdata)
> return ERR_PTR(-ENOMEM);
>
> + // Step 2
> + // One RGB multiled, num_channels = 1
> num_channels = of_get_available_child_count(np);
> if (num_channels == 0) {
> dev_err(dev, "no LED channels\n");
> return ERR_PTR(-EINVAL);
> }
>
> + dev_err(dev, "LED channels: %d\n", num_channels);
> cfg = devm_kcalloc(dev, num_channels, sizeof(*cfg), GFP_KERNEL);
> if (!cfg)
> return ERR_PTR(-ENOMEM);
>
> pdata->led_config = &cfg[0];
> pdata->num_channels = num_channels;
> + // LP5562 max_channel = 4
> cfg->max_channel = chip->cfg->max_channel;
>
> for_each_available_child_of_node(np, child) {
> @@ -1277,6 +1309,7 @@ int lp55xx_probe(struct i2c_client *client)
>
> if (!pdata) {
> if (np) {
> + // Step 1
> pdata = lp55xx_of_populate_pdata(&client->dev, np,
> chip);
> if (IS_ERR(pdata))
> @@ -1316,6 +1349,7 @@ int lp55xx_probe(struct i2c_client *client)
>
> dev_info(&client->dev, "%s Programmable led chip found\n", id->name);
>
> + // Step 7
> ret = lp55xx_register_leds(led, chip);
> if (ret)
> goto err_out;
> --
> 2.43.0
>
--
Lee Jones [李琼斯]
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