[PATCH 08/11] drm/i915/dsb: Add i915.enable_dsb module parameter

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

As we extend the use of DSB for critical pipe/plane register
programming, it'll be nice to have an escape valve at hand,
in case things go very poorly. To that end, add a i915.enable_dsb
modparam by which we can force the driver to take the pure mmio
path instead.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_params.c | 3 +++
 drivers/gpu/drm/i915/display/intel_display_params.h | 1 +
 drivers/gpu/drm/i915/display/intel_dsb.c            | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display_params.c b/drivers/gpu/drm/i915/display/intel_display_params.c
index aebdb7b59dbf..449a31767791 100644
--- a/drivers/gpu/drm/i915/display/intel_display_params.c
+++ b/drivers/gpu/drm/i915/display/intel_display_params.c
@@ -54,6 +54,9 @@ intel_display_param_named_unsafe(enable_dc, int, 0400,
 intel_display_param_named_unsafe(enable_dpt, bool, 0400,
 	"Enable display page table (DPT) (default: true)");
 
+intel_display_param_named_unsafe(enable_dsb, bool, 0600,
+	"Enable display state buffer (DSB) (default: true)");
+
 intel_display_param_named_unsafe(enable_sagv, bool, 0400,
 	"Enable system agent voltage/frequency scaling (SAGV) (default: true)");
 
diff --git a/drivers/gpu/drm/i915/display/intel_display_params.h b/drivers/gpu/drm/i915/display/intel_display_params.h
index 1208a62c16d2..48c29c55c939 100644
--- a/drivers/gpu/drm/i915/display/intel_display_params.h
+++ b/drivers/gpu/drm/i915/display/intel_display_params.h
@@ -31,6 +31,7 @@ struct drm_i915_private;
 	param(int, vbt_sdvo_panel_type, -1, 0400) \
 	param(int, enable_dc, -1, 0400) \
 	param(bool, enable_dpt, true, 0400) \
+	param(bool, enable_dsb, true, 0600) \
 	param(bool, enable_sagv, true, 0600) \
 	param(int, disable_power_well, -1, 0400) \
 	param(bool, enable_ips, true, 0600) \
diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
index bee48ac419ce..2ab3765f6c06 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.c
+++ b/drivers/gpu/drm/i915/display/intel_dsb.c
@@ -460,6 +460,9 @@ struct intel_dsb *intel_dsb_prepare(struct intel_atomic_state *state,
 	if (!HAS_DSB(i915))
 		return NULL;
 
+	if (!i915->display.params.enable_dsb)
+		return NULL;
+
 	/* TODO: DSB is broken in Xe KMD, so disabling it until fixed */
 	if (!IS_ENABLED(I915))
 		return NULL;
-- 
2.44.2