drm/i915: Allow switching away via vga-switcheroo if uninitialized

Always allow switching away via vga-switcheroo if the display is
uninitalized. Instead prevent switching to i915 if the device has
not been initialized.

This issue was introduced by commit 5df7bd1 ("drm/i915: skip
display initialization when there is no display") protected, which
protects code paths from being executed on uninitialized devices.
In the case of vga-switcheroo, we want to allow a switch away from
i915's device. So run vga_switcheroo_process_delayed_switch() and
test in the switcheroo callbacks if the i915 device is available.

Fixes: 5df7bd1 ("drm/i915: skip display initialization when there is no display")
Signed-off-by: Thomas Zimmermann <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Cc: Radhakrishna Sripada <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Cc: José Roberto de Souza <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: "Ville Syrjälä" <[email protected]>
Cc: Manasi Navare <[email protected]>
Cc: Stanislav Lisovskiy <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: "Jouni Högander" <[email protected]>
Cc: Uma Shankar <[email protected]>
Cc: Ankit Nautiyal <[email protected]>
Cc: "Jason A. Donenfeld" <[email protected]>
Cc: Matt Roper <[email protected]>
Cc: Ramalingam C <[email protected]>
Cc: Thomas Zimmermann <[email protected]>
Cc: Andi Shyti <[email protected]>
Cc: Andrzej Hajda <[email protected]>
Cc: "José Roberto de Souza" <[email protected]>
Cc: Julia Lawall <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v5.14+
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Thomas Zimmermann

drivers/gpu/drm/i915/i915_driver.c

@@ -1073,8 +1073,7 @@ static void i915_driver_lastclose(struct drm_device *dev)
 
 	intel_fbdev_restore_mode(dev);
 
-	if (HAS_DISPLAY(i915))
-		vga_switcheroo_process_delayed_switch();
+	vga_switcheroo_process_delayed_switch();
 }
 
 static void i915_driver_postclose(struct drm_device *dev, struct drm_file *file)

drivers/gpu/drm/i915/i915_switcheroo.c

@@ -19,6 +19,10 @@ static void i915_switcheroo_set_state(struct pci_dev *pdev,
 		dev_err(&pdev->dev, "DRM not initialized, aborting switch.\n");
 		return;
 	}
+	if (!HAS_DISPLAY(i915)) {
+		dev_err(&pdev->dev, "Device state not initialized, aborting switch.\n");
+		return;
+	}
 
 	if (state == VGA_SWITCHEROO_ON) {
 		drm_info(&i915->drm, "switched on\n");
@@ -44,7 +48,7 @@ static bool i915_switcheroo_can_switch(struct pci_dev *pdev)
 	 * locking inversion with the driver load path. And the access here is
 	 * completely racy anyway. So don't bother with locking for now.
 	 */
-	return i915 && atomic_read(&i915->drm.open_count) == 0;
+	return i915 && HAS_DISPLAY(i915) && atomic_read(&i915->drm.open_count) == 0;
 }
 
 static const struct vga_switcheroo_client_ops i915_switcheroo_ops = {