drm/i915/dsb: Add i915.enable_dsb module parameter

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.

v2: Use 0400 permissions for the actual modparam (Jani)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240611133344.30673-9-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_display_params.c b/drivers/gpu/drm/i915/display/intel_display_params.c
index 79107607a6ff581e79e7d89f1242f1e4e43ab0b2..e82bd72d32faf4af94aaf72da3d307cc372f59c3 100644 (file)
--- 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, 0400,
+       "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 1208a62c16d283f78b047d2b5181e1ed56df16fa..48c29c55c939bc1040a9c217568a7d079ab701b2 100644 (file)
--- 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 bee48ac419cebe8997544158bfe715391e9ee739..2ab3765f6c062314686ccc04be4dbe869ca694c7 100644 (file)
--- 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;