[PATCH] drm/i915/backlight: Fix divide by 0 error in i9xx_set_backlight

[Jani Nikula]

On Tue, 19 Aug 2025, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> pwm_level_max maybe 0 we do throw a warning but move ahead with
> execution which may later cause a /0 error.

This is not supposed to happen, so don't overcomplicate.

if (warn on)
	return

>
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_backlight.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
> index e007380e9a63..d0e9de8ab834 100644
> --- a/drivers/gpu/drm/i915/display/intel_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_backlight.c
> @@ -234,6 +234,7 @@ static void i9xx_set_backlight(const struct drm_connector_state *conn_state, u32
>  	struct intel_connector *connector = to_intel_connector(conn_state->connector);
>  	struct intel_display *display = to_intel_display(connector);
>  	struct intel_panel *panel = &connector->panel;
> +	u32 max_level = panel->backlight.pwm_level_max ?: 1;
>  	u32 tmp, mask;
>  
>  	drm_WARN_ON(display->drm, panel->backlight.pwm_level_max == 0);
> @@ -242,7 +243,7 @@ static void i9xx_set_backlight(const struct drm_connector_state *conn_state, u32
>  		struct pci_dev *pdev = to_pci_dev(display->drm->dev);
>  		u8 lbpc;
>  
> -		lbpc = level * 0xfe / panel->backlight.pwm_level_max + 1;
> +		lbpc = level * 0xfe / max_level + 1;
>  		level /= lbpc;
>  		pci_write_config_byte(pdev, LBPC, lbpc);
>  	}

-- 
Jani Nikula, Intel