drm/i915/dsi: Init panel-enable GPIO to low when the LCD is initially off (v2)

When the LCD has not been turned on by the firmware/GOP, because e.g. the
device was booted with an external monitor connected over HDMI, we should
not turn on the panel-enable GPIO when we request it.

Turning on the panel-enable GPIO when we request it, means we turn it on
too early in the init-sequence, which causes some panels to not correctly
light up.

This commits adds a panel_is_on parameter to intel_dsi_vbt_gpio_init()
and makes intel_dsi_vbt_gpio_init() set the initial GPIO value accordingly.

This fixes the panel not lighting up on a Thundersoft TST168 tablet when
booted with an external monitor connected over HDMI.

Changes in v2:
- Call intel_dsi_get_hw_state() to check if the panel is on instead of
  relying on the current_mode pointer
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191216205122.1850923-4-hdegoede@redhat.com

drivers/gpu/drm/i915/display/intel_dsi.h

@@ -203,7 +203,7 @@ void bxt_dsi_reset_clocks(struct intel_encoder *encoder, enum port port);
 
 /* intel_dsi_vbt.c */
 bool intel_dsi_vbt_init(struct intel_dsi *intel_dsi, u16 panel_id);
-void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi);
+void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi, bool panel_is_on);
 void intel_dsi_vbt_gpio_cleanup(struct intel_dsi *intel_dsi);
 void intel_dsi_vbt_exec_sequence(struct intel_dsi *intel_dsi,
 				 enum mipi_seq seq_id);

drivers/gpu/drm/i915/display/intel_dsi_vbt.c

@@ -688,17 +688,16 @@ bool intel_dsi_vbt_init(struct intel_dsi *intel_dsi, u16 panel_id)
  * On some BYT/CHT devs some sequences are incomplete and we need to manually
  * control some GPIOs.
  */
-void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi)
+void intel_dsi_vbt_gpio_init(struct intel_dsi *intel_dsi, bool panel_is_on)
 {
 	struct drm_device *dev = intel_dsi->base.base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct mipi_config *mipi_config = dev_priv->vbt.dsi.config;
+	enum gpiod_flags flags = panel_is_on ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
 
 	if ((IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) &&
 	    mipi_config->pwm_blc == PPS_BLC_PMIC) {
-		intel_dsi->gpio_panel =
-			gpiod_get(dev->dev, "panel", GPIOD_OUT_HIGH);
-
+		intel_dsi->gpio_panel = gpiod_get(dev->dev, "panel", flags);
 		if (IS_ERR(intel_dsi->gpio_panel)) {
 			DRM_ERROR("Failed to own gpio for panel control\n");
 			intel_dsi->gpio_panel = NULL;

drivers/gpu/drm/i915/display/vlv_dsi.c

@@ -1815,6 +1815,7 @@ void vlv_dsi_init(struct drm_i915_private *dev_priv)
 	struct drm_connector *connector;
 	struct drm_display_mode *current_mode, *fixed_mode;
 	enum port port;
+	enum pipe pipe;
 
 	DRM_DEBUG_KMS("\n");
 
@@ -1913,7 +1914,8 @@ void vlv_dsi_init(struct drm_i915_private *dev_priv)
 
 	vlv_dphy_param_init(intel_dsi);
 
-	intel_dsi_vbt_gpio_init(intel_dsi);
+	intel_dsi_vbt_gpio_init(intel_dsi,
+				intel_dsi_get_hw_state(intel_encoder, &pipe));
 
 	drm_connector_init(dev, connector, &intel_dsi_connector_funcs,
 			   DRM_MODE_CONNECTOR_DSI);