On Wed, 13 May 2026, Suraj Kandpal <[email protected]> wrote:
> In full-AUX VESA mode (aux_enable && aux_set) the driver never touches
> the native PCH PWM. If BIOS left PWM CTL register enabled, the PCH PWM
> keeps system alive during s2idle and blocks S0ix.
> Always run pwm_funcs->setup() so pwm_enabled reflects real HW state,
> and on first enable in full-AUX mode call pwm_funcs->disable() once to
> clear the stale bit. Runtime behaviour is otherwise unchanged.
>
> Fixes: 40d2f5820951 ("drm/i915/backlight: Remove try_vesa_interface")
> Signed-off-by: Suraj Kandpal <[email protected]>
> ---
> .../drm/i915/display/intel_dp_aux_backlight.c | 32 +++++++++++++------
> 1 file changed, 23 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> index a8d56ebf06a2..c828c568fb8b 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -496,6 +496,17 @@ intel_dp_aux_vesa_enable_backlight(const struct
> intel_crtc_state *crtc_state,
> struct intel_panel *panel = &connector->panel;
> struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
>
> + /*
> + * In full AUX VESA mode the native PWM is never driven by us. If BIOS
> + * left it enabled, the PCH PWM keeps the system alive and blocks
> + * S0ix. Sanitize it once via pwm_funcs->disable.
> + */
> + if (panel->backlight.edp.vesa.info.aux_enable &&
> + panel->backlight.edp.vesa.info.aux_set &&
> + panel->backlight.pwm_enabled)
> + panel->backlight.pwm_funcs->disable(conn_state,
> +
> intel_backlight_invert_pwm_level(connector, 0));
> +
> if (!(panel->backlight.edp.vesa.info.aux_enable ||
> panel->backlight.edp.vesa.info.luminance_set)) {
> u32 pwm_level;
> @@ -558,15 +569,18 @@ static int intel_dp_aux_vesa_setup_backlight(struct
> intel_connector *connector,
>
> panel->backlight.edp.vesa.info.luminance_set),
> backlight_unit_str(panel));
>
> - if (!panel->backlight.edp.vesa.info.aux_set ||
> - !panel->backlight.edp.vesa.info.aux_enable) {
> - ret = panel->backlight.pwm_funcs->setup(connector, pipe);
> - if (ret < 0) {
> - drm_err(display->drm,
> - "[CONNECTOR:%d:%s] Failed to setup PWM
> backlight controls for eDP backlight: %d\n",
> - connector->base.base.id, connector->base.name,
> ret);
> - return ret;
> - }
> + /*
> + * Always probe the native PWM HW state so panel->backlight.pwm_enabled
> + * reflects what BIOS left behind. Required for the full-AUX VESA path
> + * to detect and sanitize a BIOS-enabled PCH PWM that would otherwise
> + * block S0ix.
> + */
> + ret = panel->backlight.pwm_funcs->setup(connector, pipe);
This will log something like "Using native PWM for backlight control" in
dmesg, which is going to be wildly confusing for AUX backlight.
BR,
Jani.
> + if (ret < 0) {
> + drm_err(display->drm,
> + "[CONNECTOR:%d:%s] Failed to setup PWM backlight
> controls for eDP backlight: %d\n",
> + connector->base.base.id, connector->base.name, ret);
> + return ret;
> }
>
> if (panel->backlight.edp.vesa.info.luminance_set) {
--
Jani Nikula, Intel
