Re: [PATCH 2/9] backlight: qcom-wled: fix string detection brightness on WLED5

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] qcom-wled: missing brightness sync toggle for WLED4
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commit 80c30ca9ff45480f825b4f3ca26c694d9fa71acf
Author: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

backlight: qcom-wled: fix string detection brightness on WLED5

This patch updates the auto string detection logic to properly latch new
brightness values for WLED5. It introduces a helper function to set the
brightness and apply the version-specific sync toggle.

> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index f2e0430cccbca..6fbac6a4c29b8 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -577,6 +577,17 @@ static irqreturn_t wled_short_irq_handler(int irq, void *_wled)
>  
>  #define AUTO_DETECT_BRIGHTNESS		200
>  
> +static int wled_auto_detect_set_brightness(struct wled *wled, u16 brightness)
> +{
> +	int rc;
> +
> +	rc = wled->wled_set_brightness(wled, brightness);
> +	if (rc < 0 || wled->version < 5)
> +		return rc;

[Severity: Medium]
Does this code introduce a regression for WLED4 devices by missing the
brightness sync toggle?

During WLED4 auto string detection, the code updates the brightness to a low
test value, but it appears to return without latching it. Looking at the
standard brightness update path in wled_update_status(), WLED4 hardware
requires a sync toggle to apply brightness changes:

drivers/video/backlight/qcom-wled.c:wled_update_status() {
	...
	if (wled->version < 5) {
		rc = wled->wled_sync_toggle(wled);
	...
}

Without syncing the auto-detect test brightness, WLED4 might run the
detection with stale, potentially high brightness. Could this trigger false
over-voltage (OVP) faults and incorrectly mark valid LED strings as
disconnected?

> +
> +	return wled5_mod_sync_toggle(wled);
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20261015-sm8150-display-card-v1-0-5c14928cef29@oss.qualcomm.com?part=2