[Intel-gfx] [PATCH 2/2] drm/i915: Add lvds_channel module option

[Takashi Iwai]

Add a new module optoin lvds_channel to specify the LVDS channel mode
explicitly instead of probing the LVDS register value set by BIOS.
This will be helpful when VBT is broken or incompatible with the
current code.

Reviewed-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 drivers/gpu/drm/i915/i915_drv.c      |    6 ++++++
 drivers/gpu/drm/i915/i915_drv.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |    5 +++++
 3 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 308f819..92875f0 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -80,6 +80,12 @@ MODULE_PARM_DESC(lvds_downclock,
 		"Use panel (LVDS/eDP) downclocking for power savings "
 		"(default: false)");
 
+int i915_lvds_channel_mode __read_mostly;
+module_param_named(lvds_channel_mode, i915_lvds_channel_mode, int, 0600);
+MODULE_PARM_DESC(lvds_channel_mode,
+		 "Specify LVDS channel mode "
+		 "(0=probe BIOS [default], 1=single-channel, 2=dual-channel)");
+
 int i915_panel_use_ssc __read_mostly = -1;
 module_param_named(lvds_use_ssc, i915_panel_use_ssc, int, 0600);
 MODULE_PARM_DESC(lvds_use_ssc,
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8c8e488..1422431 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1014,6 +1014,7 @@ extern int i915_panel_ignore_lid __read_mostly;
 extern unsigned int i915_powersave __read_mostly;
 extern int i915_semaphores __read_mostly;
 extern unsigned int i915_lvds_downclock __read_mostly;
+extern int i915_lvds_channel_mode __read_mostly;
 extern int i915_panel_use_ssc __read_mostly;
 extern int i915_vbt_sdvo_panel_type __read_mostly;
 extern int i915_enable_rc6 __read_mostly;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d7e6b76..3a60324 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -360,6 +360,11 @@ static bool is_dual_link_lvds(struct drm_i915_private *dev_priv,
 			      unsigned int reg)
 {
 	unsigned int val;
+
+	/* use the module option value if specified */
+	if (i915_lvds_channel_mode > 0)
+		return i915_lvds_channel_mode == 2;
+
 	/* BIOS should set the proper LVDS register value at boot, but
 	 * in reality, it doesn't set the value when the lid is closed;
 	 * thus when a machine is booted with the lid closed, the LVDS
-- 
1.7.9.2