Patch "backlight: lp855x: Initialize PWM state on first brightness change" has been added to the 6.5-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    backlight: lp855x: Initialize PWM state on first brightness change

to the 6.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     backlight-lp855x-initialize-pwm-state-on-first-brigh.patch
and it can be found in the queue-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7f96da571393b4fa88947642621cefb0e0d032df
Author: Artur Weber <aweber.kernel@xxxxxxxxx>
Date:   Fri Jul 14 14:14:39 2023 +0200

    backlight: lp855x: Initialize PWM state on first brightness change
    
    [ Upstream commit 4c09e20b3c85f60353ace21092e34f35f5e3ab00 ]
    
    As pointed out by Uwe Kleine-König[1], the changes introduced in
    commit c1ff7da03e16 ("video: backlight: lp855x: Get PWM for PWM mode
    during probe") caused the PWM state set up by the bootloader to be
    re-set when the driver is probed. This differs from the behavior from
    before that patch, where the PWM state would be initialized on the
    first brightness change.
    
    Fix this by moving the PWM state initialization into the PWM control
    function. Add a new variable, needs_pwm_init, to the device info struct
    to allow us to check whether we need the initialization, or whether it
    has already been done.
    
    [1] https://lore.kernel.org/lkml/20230614083953.e4kkweddjz7wztby@xxxxxxxxxxxxxx/
    
    Fixes: c1ff7da03e16 ("video: backlight: lp855x: Get PWM for PWM mode during probe")
    Signed-off-by: Artur Weber <aweber.kernel@xxxxxxxxx>
    Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230714121440.7717-2-aweber.kernel@xxxxxxxxx
    Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index 1c9e921bca14a..349ec324bc1ea 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -71,6 +71,7 @@ struct lp855x {
 	struct device *dev;
 	struct lp855x_platform_data *pdata;
 	struct pwm_device *pwm;
+	bool needs_pwm_init;
 	struct regulator *supply;	/* regulator for VDD input */
 	struct regulator *enable;	/* regulator for EN/VDDIO input */
 };
@@ -220,7 +221,15 @@ static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 {
 	struct pwm_state state;
 
-	pwm_get_state(lp->pwm, &state);
+	if (lp->needs_pwm_init) {
+		pwm_init_state(lp->pwm, &state);
+		/* Legacy platform data compatibility */
+		if (lp->pdata->period_ns > 0)
+			state.period = lp->pdata->period_ns;
+		lp->needs_pwm_init = false;
+	} else {
+		pwm_get_state(lp->pwm, &state);
+	}
 
 	state.duty_cycle = div_u64(br * state.period, max_br);
 	state.enabled = state.duty_cycle;
@@ -387,7 +396,6 @@ static int lp855x_probe(struct i2c_client *cl)
 	const struct i2c_device_id *id = i2c_client_get_device_id(cl);
 	const struct acpi_device_id *acpi_id = NULL;
 	struct device *dev = &cl->dev;
-	struct pwm_state pwmstate;
 	struct lp855x *lp;
 	int ret;
 
@@ -470,15 +478,11 @@ static int lp855x_probe(struct i2c_client *cl)
 		else
 			return dev_err_probe(dev, ret, "getting PWM\n");
 
+		lp->needs_pwm_init = false;
 		lp->mode = REGISTER_BASED;
 		dev_dbg(dev, "mode: register based\n");
 	} else {
-		pwm_init_state(lp->pwm, &pwmstate);
-		/* Legacy platform data compatibility */
-		if (lp->pdata->period_ns > 0)
-			pwmstate.period = lp->pdata->period_ns;
-		pwm_apply_state(lp->pwm, &pwmstate);
-
+		lp->needs_pwm_init = true;
 		lp->mode = PWM_BASED;
 		dev_dbg(dev, "mode: PWM based\n");
 	}