drm/nouveau: support fetching LVDS EDID from ACPI

Based on a patch from Matthew Garrett.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Matthew Garrett <mjg@redhat.com>

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -3,6 +3,7 @@
 #include <linux/slab.h>
 #include <acpi/acpi_drivers.h>
 #include <acpi/acpi_bus.h>
+#include <acpi/video.h>
 
 #include "drmP.h"
 #include "drm.h"
@@ -11,6 +12,7 @@
 #include "nouveau_drv.h"
 #include "nouveau_drm.h"
 #include "nv50_display.h"
+#include "nouveau_connector.h"
 
 #include <linux/vga_switcheroo.h>
 
@@ -259,3 +261,37 @@ int nouveau_acpi_get_bios_chunk(uint8_t *bios, int offset, int len)
 {
 	return nouveau_rom_call(nouveau_dsm_priv.rom_handle, bios, offset, len);
 }
+
+int
+nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector)
+{
+	struct nouveau_connector *nv_connector = nouveau_connector(connector);
+	struct acpi_device *acpidev;
+	acpi_handle handle;
+	int type, ret;
+	void *edid;
+
+	switch (connector->connector_type) {
+	case DRM_MODE_CONNECTOR_LVDS:
+	case DRM_MODE_CONNECTOR_eDP:
+		type = ACPI_VIDEO_DISPLAY_LCD;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	handle = DEVICE_ACPI_HANDLE(&dev->pdev->dev);
+	if (!handle)
+		return -ENODEV;
+
+	ret = acpi_bus_get_device(handle, &acpidev);
+	if (ret)
+		return -ENODEV;
+
+	ret = acpi_video_get_edid(acpidev, type, -1, &edid);
+	if (ret < 0)
+		return ret;
+
+	nv_connector->edid = edid;
+	return 0;
+}

drivers/gpu/drm/nouveau/nouveau_bios.c

@@ -5622,7 +5622,9 @@ parse_dcb20_entry(struct drm_device *dev, struct dcb_table *dcb,
 			if (conf & 0x4 || conf & 0x8)
 				entry->lvdsconf.use_power_scripts = true;
 		} else {
-			mask = ~0x5;
+			mask = ~0x7;
+			if (conf & 0x2)
+				entry->lvdsconf.use_acpi_for_edid = true;
 			if (conf & 0x4)
 				entry->lvdsconf.use_power_scripts = true;
 		}

drivers/gpu/drm/nouveau/nouveau_bios.h

@@ -118,6 +118,7 @@ struct dcb_entry {
 		struct {
 			struct sor_conf sor;
 			bool use_straps_for_mode;
+			bool use_acpi_for_edid;
 			bool use_power_scripts;
 		} lvdsconf;
 		struct {

drivers/gpu/drm/nouveau/nouveau_connector.c

@@ -327,12 +327,29 @@ nouveau_connector_detect_lvds(struct drm_connector *connector)
 	if (!nv_encoder)
 		return connector_status_disconnected;
 
+	/* Try retrieving EDID via DDC */
 	if (!dev_priv->vbios.fp_no_ddc) {
 		status = nouveau_connector_detect(connector);
 		if (status == connector_status_connected)
 			goto out;
 	}
 
+	/* On some laptops (Sony, i'm looking at you) there appears to
+	 * be no direct way of accessing the panel's EDID.  The only
+	 * option available to us appears to be to ask ACPI for help..
+	 *
+	 * It's important this check's before trying straps, one of the
+	 * said manufacturer's laptops are configured in such a way
+	 * the nouveau decides an entry in the VBIOS FP mode table is
+	 * valid - it's not (rh#613284)
+	 */
+	if (nv_encoder->dcb->lvdsconf.use_acpi_for_edid) {
+		if (!nouveau_acpi_edid(dev, connector)) {
+			status = connector_status_connected;
+			goto out;
+		}
+	}
+
 	/* If no EDID found above, and the VBIOS indicates a hardcoded
 	 * modeline is avalilable for the panel, set it as the panel's
 	 * native mode and exit.

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -827,11 +827,13 @@ void nouveau_register_dsm_handler(void);
 void nouveau_unregister_dsm_handler(void);
 int nouveau_acpi_get_bios_chunk(uint8_t *bios, int offset, int len);
 bool nouveau_acpi_rom_supported(struct pci_dev *pdev);
+int nouveau_acpi_edid(struct drm_device *, struct drm_connector *);
 #else
 static inline void nouveau_register_dsm_handler(void) {}
 static inline void nouveau_unregister_dsm_handler(void) {}
 static inline bool nouveau_acpi_rom_supported(struct pci_dev *pdev) { return false; }
 static inline int nouveau_acpi_get_bios_chunk(uint8_t *bios, int offset, int len) { return -EINVAL; }
+static inline int nouveau_acpi_edid(struct drm_device *, struct drm_connector *) { return -EINVAL; }
 #endif
 
 /* nouveau_backlight.c */