[PATCH] drm/i915: Check num_pipes before initializing or calling display hooks

[Wang Elaine <elaine.wang@intel.com>]

From: Elaine Wang <elaine.wang@intel.com>

when num_pipes is zero, it indicates display doesn't exist, so there
is no need to initialize display hooks. And to avoid calling these
uninitialized display hooks, respect num_pipes at the beginning of
intel_modeset_init_hw.

intel_init_pm() calls FBC init function and then initializes
water mark hooks. Both aren't needed when display doesn't exist. Add
checking num_pipes at the beginning of intel_init_pm().

v2: Move one check from caller to callee for consistency.
v3: Addressed Jani's Review comments(minimize the amount of the checks)
- Assign nop_init_clock_gating() to the clock gating hook when
num_pipes is zero.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>

Signed-off-by: Elaine Wang <elaine.wang@intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 6 ++++++
 drivers/gpu/drm/i915/intel_pm.c      | 8 +++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d8effd4..eb180df 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -16161,6 +16161,9 @@ static void intel_atomic_state_free(struct drm_atomic_state *state)
  */
 void intel_init_display_hooks(struct drm_i915_private *dev_priv)
 {
+	if (INTEL_INFO(dev_priv)->num_pipes == 0)
+		return;
+
 	if (INTEL_INFO(dev_priv)->gen >= 9) {
 		dev_priv->display.get_pipe_config = haswell_get_pipe_config;
 		dev_priv->display.get_initial_plane_config =
@@ -16543,6 +16546,9 @@ void intel_modeset_init_hw(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
+	if (INTEL_INFO(dev_priv)->num_pipes == 0)
+		return;
+
 	intel_update_cdclk(dev_priv);
 
 	dev_priv->atomic_cdclk_freq = dev_priv->cdclk_freq;
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 338b542..bf63ba5 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -7642,7 +7642,10 @@ static void nop_init_clock_gating(struct drm_i915_private *dev_priv)
  */
 void intel_init_clock_gating_hooks(struct drm_i915_private *dev_priv)
 {
-	if (IS_SKYLAKE(dev_priv))
+
+	if (INTEL_INFO(dev_priv)->num_pipes == 0)
+		dev_priv->display.init_clock_gating = nop_init_clock_gating;
+	else if (IS_SKYLAKE(dev_priv))
 		dev_priv->display.init_clock_gating = skylake_init_clock_gating;
 	else if (IS_KABYLAKE(dev_priv))
 		dev_priv->display.init_clock_gating = kabylake_init_clock_gating;
@@ -7683,6 +7686,9 @@ void intel_init_clock_gating_hooks(struct drm_i915_private *dev_priv)
 /* Set up chip specific power management-related functions */
 void intel_init_pm(struct drm_i915_private *dev_priv)
 {
+	if (INTEL_INFO(dev_priv)->num_pipes == 0)
+		return;
+
 	intel_fbc_init(dev_priv);
 
 	/* For cxsr */
-- 
1.9.1

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