drm/i915/wopcm: Handle pre-programmed WOPCM registers

Starting from DG2, some of the programming previously done by i915 and
the GuC has been moved to the GSC and the relevant registers are no
longer writable by either CPU or GuC. This is also referred to as GuC
deprivilege.
On the i915 side, this affects the WOPCM registers: these are no longer
programmed by the driver and we do instead expect to find them already
set. This can lead to verification failures because in i915 we cheat a bit
with the WOPCM size defines, to keep the code common across platforms, by
sometimes using a smaller WOPCM size that the actual HW support (which isn't
a problem because the extra size is not needed if the FW fits in the smaller
chunk), while the pre-programmed values can use the actual size.
Given tha the new programming entity is trusted, relax the amount of the
checks done on the pre-programmed values by not limiting the max
programmed size. In the extremely unlikely scenario that the registers
have been misprogrammed, we will still fail later at DMA time.

v2: drop special case for DG2 G10 A0 (Alan)
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Cc: John Harrison <john.c.harrison@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220120212947.3440448-1-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_reg.h

@@ -94,6 +94,9 @@
 #define   GUC_ENABLE_MIA_CLOCK_GATING		(1<<15)
 #define   GUC_GEN10_SHIM_WC_ENABLE		(1<<21)
 
+#define GUC_SHIM_CONTROL2		_MMIO(0xc068)
+#define   GUC_IS_PRIVILEGED		(1<<29)
+
 #define GUC_SEND_INTERRUPT		_MMIO(0xc4c8)
 #define   GUC_SEND_TRIGGER		  (1<<0)
 #define GEN11_GUC_HOST_INTERRUPT	_MMIO(0x1901f0)

drivers/gpu/drm/i915/i915_drv.h

@@ -1577,6 +1577,9 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 #define INTEL_DISPLAY_ENABLED(dev_priv) \
 	(drm_WARN_ON(&(dev_priv)->drm, !HAS_DISPLAY(dev_priv)), !(dev_priv)->params.disable_display)
 
+#define HAS_GUC_DEPRIVILEGE(dev_priv) \
+	(INTEL_INFO(dev_priv)->has_guc_deprivilege)
+
 static inline bool run_as_guest(void)
 {
 	return !hypervisor_is_type(X86_HYPER_NATIVE);

drivers/gpu/drm/i915/i915_pci.c

@@ -1045,6 +1045,7 @@ static const struct intel_device_info dg2_info = {
 	.graphics.rel = 55,
 	.media.rel = 55,
 	PLATFORM(INTEL_DG2),
+	.has_guc_deprivilege = 1,
 	.has_64k_pages = 1,
 	.platform_engine_mask =
 		BIT(RCS0) | BIT(BCS0) |

drivers/gpu/drm/i915/intel_device_info.h

@@ -131,6 +131,7 @@ enum intel_ppgtt_type {
 	func(has_reset_engine); \
 	func(has_global_mocs); \
 	func(has_gt_uc); \
+	func(has_guc_deprivilege); \
 	func(has_l3_dpf); \
 	func(has_llc); \
 	func(has_logical_ring_contexts); \

drivers/gpu/drm/i915/intel_wopcm.c

@@ -43,6 +43,7 @@
 /* Default WOPCM size is 2MB from Gen11, 1MB on previous platforms */
 #define GEN11_WOPCM_SIZE		SZ_2M
 #define GEN9_WOPCM_SIZE			SZ_1M
+#define MAX_WOPCM_SIZE			SZ_8M
 /* 16KB WOPCM (RSVD WOPCM) is reserved from HuC firmware top. */
 #define WOPCM_RESERVED_SIZE		SZ_16K
 
@@ -207,6 +208,14 @@ static bool __wopcm_regs_locked(struct intel_uncore *uncore,
 	return true;
 }
 
+static bool __wopcm_regs_writable(struct intel_uncore *uncore)
+{
+	if (!HAS_GUC_DEPRIVILEGE(uncore->i915))
+		return true;
+
+	return intel_uncore_read(uncore, GUC_SHIM_CONTROL2) & GUC_IS_PRIVILEGED;
+}
+
 /**
  * intel_wopcm_init() - Initialize the WOPCM structure.
  * @wopcm: pointer to intel_wopcm.
@@ -224,18 +233,19 @@ void intel_wopcm_init(struct intel_wopcm *wopcm)
 	u32 guc_fw_size = intel_uc_fw_get_upload_size(&gt->uc.guc.fw);
 	u32 huc_fw_size = intel_uc_fw_get_upload_size(&gt->uc.huc.fw);
 	u32 ctx_rsvd = context_reserved_size(i915);
+	u32 wopcm_size = wopcm->size;
 	u32 guc_wopcm_base;
 	u32 guc_wopcm_size;
 
 	if (!guc_fw_size)
 		return;
 
-	GEM_BUG_ON(!wopcm->size);
+	GEM_BUG_ON(!wopcm_size);
 	GEM_BUG_ON(wopcm->guc.base);
 	GEM_BUG_ON(wopcm->guc.size);
-	GEM_BUG_ON(guc_fw_size >= wopcm->size);
-	GEM_BUG_ON(huc_fw_size >= wopcm->size);
-	GEM_BUG_ON(ctx_rsvd + WOPCM_RESERVED_SIZE >= wopcm->size);
+	GEM_BUG_ON(guc_fw_size >= wopcm_size);
+	GEM_BUG_ON(huc_fw_size >= wopcm_size);
+	GEM_BUG_ON(ctx_rsvd + WOPCM_RESERVED_SIZE >= wopcm_size);
 
 	if (i915_inject_probe_failure(i915))
 		return;
@@ -243,6 +253,24 @@ void intel_wopcm_init(struct intel_wopcm *wopcm)
 	if (__wopcm_regs_locked(gt->uncore, &guc_wopcm_base, &guc_wopcm_size)) {
 		drm_dbg(&i915->drm, "GuC WOPCM is already locked [%uK, %uK)\n",
 			guc_wopcm_base / SZ_1K, guc_wopcm_size / SZ_1K);
+		/*
+		 * Note that to keep things simple (i.e. avoid different
+		 * defines per platform) our WOPCM math doesn't always use the
+		 * actual WOPCM size, but a value that is less or equal to it.
+		 * This is perfectly fine when i915 programs the registers, but
+		 * on platforms with GuC deprivilege the registers are not
+		 * writable from i915 and are instead pre-programmed by the
+		 * bios/IFWI, so there might be a mismatch of sizes.
+		 * Instead of handling the size difference, we trust that the
+		 * programmed values make sense and disable the relevant check
+		 * by using the maximum possible WOPCM size in the verification
+		 * math. In the extremely unlikely case that the registers
+		 * were pre-programmed with an invalid value, we will still
+		 * gracefully fail later during the GuC/HuC dma.
+		 */
+		if (!__wopcm_regs_writable(gt->uncore))
+			wopcm_size = MAX_WOPCM_SIZE;
+
 		goto check;
 	}
 
@@ -257,17 +285,17 @@ void intel_wopcm_init(struct intel_wopcm *wopcm)
 	 * Need to clamp guc_wopcm_base now to make sure the following math is
 	 * correct. Formal check of whole WOPCM layout will be done below.
 	 */
-	guc_wopcm_base = min(guc_wopcm_base, wopcm->size - ctx_rsvd);
+	guc_wopcm_base = min(guc_wopcm_base, wopcm_size - ctx_rsvd);
 
 	/* Aligned remainings of usable WOPCM space can be assigned to GuC. */
-	guc_wopcm_size = wopcm->size - ctx_rsvd - guc_wopcm_base;
+	guc_wopcm_size = wopcm_size - ctx_rsvd - guc_wopcm_base;
 	guc_wopcm_size &= GUC_WOPCM_SIZE_MASK;
 
 	drm_dbg(&i915->drm, "Calculated GuC WOPCM [%uK, %uK)\n",
 		guc_wopcm_base / SZ_1K, guc_wopcm_size / SZ_1K);
 
 check:
-	if (__check_layout(i915, wopcm->size, guc_wopcm_base, guc_wopcm_size,
+	if (__check_layout(i915, wopcm_size, guc_wopcm_base, guc_wopcm_size,
 			   guc_fw_size, huc_fw_size)) {
 		wopcm->guc.base = guc_wopcm_base;
 		wopcm->guc.size = guc_wopcm_size;