[Intel-gfx] [PATCH 1/2] drm/i915: Use a modparam to restrict exposed engines

[Chris Wilson]

Allow the user to restrict the available set of engines via a module
parameter.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Stuart Summers <stuart.summers at intel.com>
Cc: Andi Shyti <andi.shyti at intel.com>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Martin Peres <martin.peres at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 35 ++++++++++++++++-------
 drivers/gpu/drm/i915/i915_gem.c           |  5 ++++
 drivers/gpu/drm/i915/i915_params.c        |  4 +++
 drivers/gpu/drm/i915/i915_params.h        |  1 +
 4 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 80fd072ac719..690da64ec256 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -389,6 +389,29 @@ void intel_engines_cleanup(struct drm_i915_private *i915)
 	}
 }
 
+static bool engine_available(struct drm_i915_private *i915, int id)
+{
+	/* uAPI -- modparam bits must be consistent between kernels */
+	static const unsigned int param_bit[] = {
+		[RCS0]  = BIT(0),
+		[VCS0]  = BIT(1),
+		[BCS0]  = BIT(2),
+		[VECS0] = BIT(3),
+		[VCS1]  = BIT(4),
+		[VCS2]  = BIT(5),
+		[VCS3]  = BIT(6),
+		[VECS1] = BIT(7),
+	};
+
+	if (!HAS_ENGINE(i915, id))
+		return false;
+
+	if (!(i915_modparams.engines & param_bit[id]))
+		return false;
+
+	return true;
+}
+
 /**
  * intel_engines_init_mmio() - allocate and prepare the Engine Command Streamers
  * @i915: the i915 device
@@ -397,7 +420,6 @@ void intel_engines_cleanup(struct drm_i915_private *i915)
  */
 int intel_engines_init_mmio(struct drm_i915_private *i915)
 {
-	struct intel_device_info *device_info = mkwrite_device_info(i915);
 	const unsigned int engine_mask = INTEL_INFO(i915)->engine_mask;
 	unsigned int mask = 0;
 	unsigned int i;
@@ -411,7 +433,7 @@ int intel_engines_init_mmio(struct drm_i915_private *i915)
 		return -ENODEV;
 
 	for (i = 0; i < ARRAY_SIZE(intel_engines); i++) {
-		if (!HAS_ENGINE(i915, i))
+		if (!engine_available(i915, i))
 			continue;
 
 		err = intel_engine_setup(&i915->gt, i);
@@ -421,14 +443,7 @@ int intel_engines_init_mmio(struct drm_i915_private *i915)
 		mask |= BIT(i);
 	}
 
-	/*
-	 * Catch failures to update intel_engines table when the new engines
-	 * are added to the driver by a warning and disabling the forgotten
-	 * engines.
-	 */
-	if (WARN_ON(mask != engine_mask))
-		device_info->engine_mask = mask;
-
+	mkwrite_device_info(i915)->engine_mask = mask;
 	RUNTIME_INFO(i915)->num_engines = hweight32(mask);
 
 	intel_gt_check_and_clear_faults(&i915->gt);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 3d3fda4cae99..bb25731466a9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1308,6 +1308,11 @@ int i915_gem_init(struct drm_i915_private *dev_priv)
 {
 	int ret;
 
+	if (!RUNTIME_INFO(dev_priv)->num_engines) {
+		intel_gt_set_wedged_on_init(&dev_priv->gt);
+		return 0;
+	}
+
 	/* We need to fallback to 4K pages if host doesn't support huge gtt. */
 	if (intel_vgpu_active(dev_priv) && !intel_vgpu_has_huge_gtt(dev_priv))
 		mkwrite_device_info(dev_priv)->page_sizes =
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 296452f9efe4..27813bd79aa8 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -44,6 +44,10 @@ i915_param_named(modeset, int, 0400,
 	"Use kernel modesetting [KMS] (0=disable, "
 	"1=on, -1=force vga console preference [default])");
 
+i915_param_named(engines, uint, 0400,
+	"Only expose selected command streamers [GPU engines] (0=disable GPU, "
+	"-1/0xffffffff enable all [default]). Each bit corresponds to a different phyiscal engine: 0=RCS0, 1=VCS0, 2=BCS0, 3=VECS0, 4=VCS1, 5=VCS2, 6=VCS3, 7=VECS1");
+
 i915_param_named_unsafe(enable_dc, int, 0400,
 	"Enable power-saving display C-states. "
 	"(-1=auto [default]; 0=disable; 1=up to DC5; 2=up to DC6)");
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index d29ade3b7de6..f876db78a59a 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -45,6 +45,7 @@ struct drm_printer;
 #define I915_PARAMS_FOR_EACH(param) \
 	param(char *, vbt_firmware, NULL) \
 	param(int, modeset, -1) \
+	param(unsigned int, engines, -1) \
 	param(int, lvds_channel_mode, 0) \
 	param(int, panel_use_ssc, -1) \
 	param(int, vbt_sdvo_panel_type, -1) \
-- 
2.23.0