drm/nouveau: do not forcibly power on lvds panels

This fix was put in place to fix a bug where the eDP panel on certain
laptops fails to respond over the aux channel after suspend.

It appears that on some systems (Dell M6600, with LVDS panel) there's a
very bad interaction with the eDP init table that causes the SOR to get
very confused and not drive the panel correctly, leading to bleed.

A DPMS off/on cycle is enough to bring it back, but, this will avoid the
problem by not touching the panel GPIOs at times we're not meant to.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

2 files changed, 26 insertions, 13 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c
index ac340ba3201..e620ba8271b 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -127,12 +127,26 @@ nouveau_connector_ddc_detect(struct drm_connector *connector,
                              struct nouveau_encoder **pnv_encoder)
 {
         struct drm_device *dev = connector->dev;
+        struct nouveau_connector *nv_connector = nouveau_connector(connector);
         struct nouveau_drm *drm = nouveau_drm(dev);
+        struct nouveau_gpio *gpio = nouveau_gpio(drm->device);
         struct nouveau_i2c *i2c = nouveau_i2c(drm->device);
-        int i;
+        struct nouveau_i2c_port *port = NULL;
+        int i, panel = -ENODEV;
+
+        /* eDP panels need powering on by us (if the VBIOS doesn't default it
+         * to on) before doing any AUX channel transactions.  LVDS panel power
+         * is handled by the SOR itself, and not required for LVDS DDC.
+         */
+        if (nv_connector->type == DCB_CONNECTOR_eDP) {
+                panel = gpio->get(gpio, 0, DCB_GPIO_PANEL_POWER, 0xff);
+                if (panel == 0) {
+                        gpio->set(gpio, 0, DCB_GPIO_PANEL_POWER, 0xff, 1);
+                        msleep(300);
+                }
+        }
 
         for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
-                struct nouveau_i2c_port *port = NULL;
                 struct nouveau_encoder *nv_encoder;
                 struct drm_mode_object *obj;
                 int id;
@@ -150,11 +164,19 @@ nouveau_connector_ddc_detect(struct drm_connector *connector,
                         port = i2c->find(i2c, nv_encoder->dcb->i2c_index);
                 if (port && nv_probe_i2c(port, 0x50)) {
                         *pnv_encoder = nv_encoder;
-                        return port;
+                        break;
                 }
+
+                port = NULL;
         }
 
-        return NULL;
+        /* eDP panel not detected, restore panel power GPIO to previous
+         * state to avoid confusing the SOR for other output types.
+         */
+        if (!port && panel == 0)
+                gpio->set(gpio, 0, DCB_GPIO_PANEL_POWER, 0xff, panel);
+
+        return port;
 }
 
 static struct nouveau_encoder *
diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
index e4188f24fc7..508b00a2ce0 100644
--- a/drivers/gpu/drm/nouveau/nouveau_display.c
+++ b/drivers/gpu/drm/nouveau/nouveau_display.c
@@ -225,15 +225,6 @@ nouveau_display_init(struct drm_device *dev)
         if (ret)
                 return ret;
 
-        /* power on internal panel if it's not already.  the init tables of
-         * some vbios default this to off for some reason, causing the
-         * panel to not work after resume
-         */
-        if (gpio && gpio->get(gpio, 0, DCB_GPIO_PANEL_POWER, 0xff) == 0) {
-                gpio->set(gpio, 0, DCB_GPIO_PANEL_POWER, 0xff, 1);
-                msleep(300);
-        }
-
         /* enable polling for external displays */
         drm_kms_helper_poll_enable(dev);