Re: [PATCH v3 2/2] backlight: Add support for Orient Chip OCP8178

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Missing PM resume initialization causes backlight to fail after system suspend.
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--- Patch [2]: [PATCH v3 2/2] backlight: Add support for Orient Chip OCP8178 ---
commit bfc20bddc55de3beb592431b21d9fc9bc3366d90
Author: Wim de With <[email protected]>

backlight: Add support for Orient Chip OCP8178

This commit adds a driver for the Orient Chip OCP8178 backlight controller.
The driver implements a vendor-specific onewire protocol over GPIO to set
static brightness levels.

> diff --git a/drivers/video/backlight/ocp8178_bl.c b/drivers/video/backlight/ocp8178_bl.c
> new file mode 100644
> index 0000000000000..6c1e8c9451f12
> --- /dev/null
> +++ b/drivers/video/backlight/ocp8178_bl.c
[ ... ]
> +static int ocp8178_bl_update_status(struct backlight_device *bl)
> +{
> +	struct ocp8178_bl *ocp8178 = bl_get_data(bl);
> +	u8 brightness = backlight_get_brightness(bl);
> +
> +	ocp8178_bl_set_brightness(ocp8178, brightness);
> +	return 0;
> +}
> +
> +static const struct backlight_ops ocp8178_bl_ops = {
> +	.options = BL_CORE_SUSPENDRESUME,
> +	.update_status = ocp8178_bl_update_status,
> +};
[ ... ]
> +static struct platform_driver ocp8178_bl_driver = {
> +	.driver = {
> +		.name = "ocp8178-bl",
> +		.of_match_table = ocp8178_bl_of_match,
> +	},
> +	.probe = ocp8178_bl_probe,
> +};

[Severity: High]
Will the backlight fail to turn on after a system suspend cycle?

Since BL_CORE_SUSPENDRESUME is set in ocp8178_bl_ops, the backlight core
calls ocp8178_bl_update_status() upon system resume. During suspend, the
GPIO controller may pull the control pin low.

If the pin remains low for more than 2.5ms (OCP8178_T_OFF_US), the chip
shuts down and will power back up in its default PWM mode.

Because ocp8178_bl_update_status() immediately sends 1-wire commands without
verifying state or re-running ocp8178_bl_enable_onewire(), will the chip
misinterpret these 1-wire signals as tiny PWM pulses instead of restoring
the brightness level?

Does the platform driver need pm_ops to re-initialize the 1-wire mode state
before the backlight core attempts to update the brightness?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2