[Intel-gfx] [PATCH]drm/i915: fix gpio register detection logic for BIOS without VBT

[Shaohua Li]

if no VBT, crt_ddc_bus will be 0, and cause we use 0 for GPIO. It's unlikely
GPIO register is 0, so don't need initialize it to -1.

Signed-off-by: Shaohua Li <shaohua.li at intel.com>
Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 57204e2..8df9753 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -258,7 +258,7 @@ typedef struct drm_i915_private {
 
 	struct notifier_block lid_notifier;
 
-	int crt_ddc_bus; /* -1 = unknown, else GPIO to use for CRT DDC */
+	int crt_ddc_bus; /* 0 = unknown, else GPIO to use for CRT DDC */
 	struct drm_i915_fence_reg fence_regs[16]; /* assume 965 */
 	int fence_reg_start; /* 4 if userland hasn't ioctl'd us yet */
 	int num_fence_regs; /* 8 on pre-965, 16 otherwise */
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 96cd256..97169ea 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -241,10 +241,6 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
 		GPIOF,
 	};
 
-	/* Set sensible defaults in case we can't find the general block
-	   or it is the wrong chipset */
-	dev_priv->crt_ddc_bus = -1;
-
 	general = find_section(bdb, BDB_GENERAL_DEFINITIONS);
 	if (general) {
 		u16 block_size = get_blocksize(general);
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 212e227..7da2b6e 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -554,7 +554,7 @@ void intel_crt_init(struct drm_device *dev)
 	else {
 		i2c_reg = GPIOA;
 		/* Use VBT information for CRT DDC if available */
-		if (dev_priv->crt_ddc_bus != -1)
+		if (dev_priv->crt_ddc_bus != 0)
 			i2c_reg = dev_priv->crt_ddc_bus;
 	}
 	intel_output->ddc_bus = intel_i2c_create(dev, i2c_reg, "CRTDDC_A");