[RFC] drm/i915: Enable fastboot by default on Skylake and newer

[Hans de Goede]

We really want to have fastboot enabled by default to avoid an ugly
modeset during boot.

Rather then enabling it everywhere, lets start with enabling it on
Skylake and newer.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 drivers/gpu/drm/i915/i915_params.c   |  6 ++++--
 drivers/gpu/drm/i915/i915_params.h   |  2 +-
 drivers/gpu/drm/i915/intel_display.c | 11 ++++++++++-
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 295e981e4a39..ff5f32a3aaf0 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -101,8 +101,10 @@ i915_param_named_unsafe(disable_power_well, int, 0400,
 
 i915_param_named_unsafe(enable_ips, int, 0600, "Enable IPS (default: true)");
 
-i915_param_named(fastboot, bool, 0600,
-	"Try to skip unnecessary mode sets at boot time (default: false)");
+i915_param_named(fastboot, int, 0600,
+	"Try to skip unnecessary mode sets at boot time "
+	"(0=disabled, 1=enabled) "
+	"Default: -1 (use per-chip default)");
 
 i915_param_named_unsafe(prefault_disable, bool, 0600,
 	"Disable page prefaulting for pread/pwrite/reloc (default:false). "
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 6c4d4a21474b..7e11aa4d1d97 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -55,10 +55,10 @@ struct drm_printer;
 	param(int, edp_vswing, 0) \
 	param(int, reset, 2) \
 	param(unsigned int, inject_load_failure, 0) \
+	param(int, fastboot, -1) \
 	/* leave bools at the end to not create holes */ \
 	param(bool, alpha_support, IS_ENABLED(CONFIG_DRM_I915_ALPHA_SUPPORT)) \
 	param(bool, enable_hangcheck, true) \
-	param(bool, fastboot, false) \
 	param(bool, prefault_disable, false) \
 	param(bool, load_detect_test, false) \
 	param(bool, force_reset_modeset_test, false) \
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 071954d255c6..62df34d30b1f 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12501,6 +12501,15 @@ static int calc_watermark_data(struct drm_atomic_state *state)
 	return 0;
 }
 
+static bool fastboot_enabled(struct drm_i915_private *dev_priv)
+{
+	if (i915_modparams.fastboot != -1)
+		return i915_modparams.fastboot;
+
+	/* Enable fastboot by default on Skylake and newer */
+	return INTEL_GEN(dev_priv) >= 9;
+}
+
 static bool can_fastset(struct drm_i915_private *dev_priv,
 			struct intel_crtc_state *old_crtc_state,
 			struct intel_crtc_state *new_crtc_state)
@@ -12510,7 +12519,7 @@ static bool can_fastset(struct drm_i915_private *dev_priv,
 		!(new_crtc_state->base.mode.private_flags & I915_MODE_FLAG_INHERITED);
 
 	/* Without fastboot, we always want to modeset the initial mode. */
-	if (reset_mode && !i915_modparams.fastboot)
+	if (reset_mode && !fastboot_enabled(dev_priv))
 		return false;
 
 	return intel_pipe_config_compare(dev_priv, old_crtc_state,
-- 
2.20.1