Merge tag 'drm-intel-gt-next-2021-08-06-1' of ssh://git.freedesktop.org/git/drm/drm-intel into drm-next

UAPI Changes:

- Add I915_MMAP_OFFSET_FIXED

  On devices with local memory `I915_MMAP_OFFSET_FIXED` is the only valid
  type. On devices without local memory, this caching mode is invalid.

  As caching mode when specifying `I915_MMAP_OFFSET_FIXED`, WC or WB will
  be used, depending on the object placement on creation. WB will be used
  when the object can only exist in system memory, WC otherwise.

  Userspace: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11888

- Reinstate the mmap ioctl for (already released) integrated Gen12 platforms

  Rationale: Otherwise media driver breaks eg. for ADL-P. Long term goal is
  still to sunset the IOCTL even for integrated and require using mmap_offset.

- Reject caching/set_domain IOCTLs on discrete

  Expected to become immutable property of the BO

- Disallow changing context parameters after first use on Gen12 and earlier
- Require setting context parameters at creation on platforms after Gen12

  Rationale (for both): Allow less dynamic changes to the context to simplify
  the implementation and avoid user shooting theirselves in the foot.

- Drop I915_CONTEXT_PARAM_RINGSIZE

  Userspace PR for compute-driver has not been merged

- Drop I915_CONTEXT_PARAM_NO_ZEROMAP

  Userspace PR for libdrm / Beignet was never landed

- Drop CONTEXT_CLONE API

  Userspace PR for Mesa was never landed

- Drop getparam support for I915_CONTEXT_PARAM_ENGINES

  Only existed for symmetry wrt. setparam, never used.

- Disallow bonding of virtual engines

  Drop the prep work, no hardware has been released needing it.

- (Implicit) Disable gpu relocations

  Media userspace was the last userspace to still use them. They
  have converted so performance can be regained with an update.

Core Changes:

- Merge topic branch 'topic/i915-ttm-2021-06-11' (from Maarten)
- Merge topic branch 'topic/revid_steppings' (from Matt R)
- Merge topic branch 'topic/xehp-dg2-definitions-2021-07-21' (from Matt R)
- Backmerges drm-next (Rodrigo)

Driver Changes:

- Initial workarounds for ADL-P (Clint)
- Preliminary code for XeHP/DG2 (Stuart, Umesh, Matt R, Prathap, Ram,
  Venkata, Akeem, Tvrtko, John, Lucas)
- Fix ADL-S DMA mask size to 39 bits (Tejas)
- Remove code for CNL (Lucas)
- Add ADL-P GuC/HuC firmwares (John)
- Update HuC to 7.9.3 for TGL/ADL-S/RKL (John)
- Fix -EDEADLK handling regression (Ville)
- Implement Wa_1508744258 for DG1 and Gen12 iGFX (Jose)
- Extend Wa_1406941453 to ADL-S (Jose)
- Drop unnecessary workarounds per stepping for SKL/BXT/ICL (Matt R)
- Use fuse info to enable SFC on Gen12 (Venkata)
- Unconditionally flush the pages on acquire on EHL/JSL (Matt A)
- Probe existence of backing struct pages upon userptr creation (Chris, Matt A)

- Add an intermediate GEM proto-context to delay real context creation (Jason)
- Implement SINGLE_TIMELINE with a syncobj (Jason)
- Set the watchdog timeout directly in intel_context_set_gem (Jason)
- Disallow userspace from creating contexts with too many engines (Jason)
- Revert "drm/i915/gem: Asynchronous cmdparser" (Jason)
- Revert "drm/i915: Propagate errors on awaiting already signaled fences" (Jason)
- Revert "drm/i915: Skip over MI_NOOP when parsing" (Jason)
- Revert "drm/i915: Shrink the GEM kmem_caches upon idling" (Daniel)
- Always let TTM handle object migration (Jason)
- Correct the locking and pin pattern for dma-buf (Thomas H, Michael R, Jason)
- Migrate to system at dma-buf attach time (Thomas, Michael R)

- MAJOR refactoring of the GuC backend code to allow for enabling on Gen11+
  (Matt B, John, Michal Wa., Fernando, Daniele, Vinay)
- Update GuC firmware interface to v62.0.0 (John, Michal Wa., Matt B)
- Add GuCRC feature to hand over the control of HW RC6 to the GuC on
  Gen12+ when GuC submission is enabled (Vinay, Sujaritha, Daniele,
  John, Tvrtko)
- Use the correct IRQ during resume and eliminate DRM IRQ midlayer (Thomas Z)
- Add pipelined page migration and clearing (Chris, Thomas H)
- Use TTM for system memory on discrete (Thomas H)
- Implement object migration for display vs. dma-buf (Thomas H)
- Perform execbuffer object locking as a separate step (Thomas H)
- Add support for explicit L3BANK steering (Matt, Daniele)
- Remove duplicated call to ops->pread (Daniel)
- Fix pagefault disabling in the first execbuf slowpath (Daniel)
- Simplify userptr locking (Thomas H)
- Improvements to the GuC CTB code (Matt B, John)
- Make GT workaround upper bounds exclusive (Matt R)
- Check for nomodeset in i915_init() first (Daniel)
- Delete now unused gpu reloc code (Daniel)

- Document RFC plans for GuC submission, DRM scheduler and new parallel
  submit uAPI (Matt B)
- Reintroduce buddy allocator this time with TTM (Matt A)
- Support forcing page size with LMEM (Matt A)
- Add i915_sched_engine to abstract a submission queue between backends (Matt B)
- Use accelerated move in TTM (Ram)
- Fix memory leaks from TTM backend (Thomas H)
- Introduce WW transaction helper (Thomas H)
- Improve debug Kconfig texts a bit (Daniel)
- Unify user object creation code (Jason)
- Use a table for i915_init/exit (Jason)
- Move slabs to module init/exit (Daniel)
- Remove now unused i915_globals (Daniel)
- Extract i915_module.c (Daniel)

- Consistently use adl-p/adl-s in WA comments (Jose)
- Finish INTEL_GEN and friends conversion (Lucas)
- Correct variable/function namings (Lucas)
- Code checker fixes (Wan, Matt A)
- Tracepoint improvements (Matt B)
- Kerneldoc improvements (Tvrtko, Jason, Matt A, Maarten)
- Selftest improvements (Chris, Matt A, Tejas, Thomas H, John, Matt B,
  Rahul, Vinay)

Signed-off-by: Dave Airlie <airlied@redhat.com>

From: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/YQ0JmYiXhGskNcrI@jlahtine-mobl.ger.corp.intel.com

1 files changed, 124 insertions, 97 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 997fbe9532c1..b619f4843b15 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -202,6 +202,68 @@ struct drm_i915_file_private {
 		struct rcu_head rcu;
 	};
 
+	/** @proto_context_lock: Guards all struct i915_gem_proto_context
+	 * operations
+	 *
+	 * This not only guards @proto_context_xa, but is always held
+	 * whenever we manipulate any struct i915_gem_proto_context,
+	 * including finalizing it on first actual use of the GEM context.
+	 *
+	 * See i915_gem_proto_context.
+	 */
+	struct mutex proto_context_lock;
+
+	/** @proto_context_xa: xarray of struct i915_gem_proto_context
+	 *
+	 * Historically, the context uAPI allowed for two methods of
+	 * setting context parameters: SET_CONTEXT_PARAM and
+	 * CONTEXT_CREATE_EXT_SETPARAM.  The former is allowed to be called
+	 * at any time while the later happens as part of
+	 * GEM_CONTEXT_CREATE.  Everything settable via one was settable
+	 * via the other.  While some params are fairly simple and setting
+	 * them on a live context is harmless such as the context priority,
+	 * others are far trickier such as the VM or the set of engines.
+	 * In order to swap out the VM, for instance, we have to delay
+	 * until all current in-flight work is complete, swap in the new
+	 * VM, and then continue.  This leads to a plethora of potential
+	 * race conditions we'd really rather avoid.
+	 *
+	 * We have since disallowed setting these more complex parameters
+	 * on active contexts.  This works by delaying the creation of the
+	 * actual context until after the client is done configuring it
+	 * with SET_CONTEXT_PARAM.  From the perspective of the client, it
+	 * has the same u32 context ID the whole time.  From the
+	 * perspective of i915, however, it's a struct i915_gem_proto_context
+	 * right up until the point where we attempt to do something which
+	 * the proto-context can't handle.  Then the struct i915_gem_context
+	 * gets created.
+	 *
+	 * This is accomplished via a little xarray dance.  When
+	 * GEM_CONTEXT_CREATE is called, we create a struct
+	 * i915_gem_proto_context, reserve a slot in @context_xa but leave
+	 * it NULL, and place the proto-context in the corresponding slot
+	 * in @proto_context_xa.  Then, in i915_gem_context_lookup(), we
+	 * first check @context_xa.  If it's there, we return the struct
+	 * i915_gem_context and we're done.  If it's not, we look in
+	 * @proto_context_xa and, if we find it there, we create the actual
+	 * context and kill the proto-context.
+	 *
+	 * In order for this dance to work properly, everything which ever
+	 * touches a struct i915_gem_proto_context is guarded by
+	 * @proto_context_lock, including context creation.  Yes, this
+	 * means context creation now takes a giant global lock but it
+	 * can't really be helped and that should never be on any driver's
+	 * fast-path anyway.
+	 */
+	struct xarray proto_context_xa;
+
+	/** @context_xa: xarray of fully created i915_gem_context
+	 *
+	 * Write access to this xarray is guarded by @proto_context_lock.
+	 * Otherwise, writers may race with finalize_create_context_locked().
+	 *
+	 * See @proto_context_xa.
+	 */
 	struct xarray context_xa;
 	struct xarray vm_xa;
 
@@ -332,15 +394,6 @@ struct drm_i915_display_funcs {
 	void (*read_luts)(struct intel_crtc_state *crtc_state);
 };
 
-enum i915_cache_level {
-	I915_CACHE_NONE = 0,
-	I915_CACHE_LLC, /* also used for snoopable memory on non-LLC */
-	I915_CACHE_L3_LLC, /* gen7+, L3 sits between the domain specifc
-			      caches, eg sampler/render caches, and the
-			      large Last-Level-Cache. LLC is coherent with
-			      the CPU, but L3 is only visible to the GPU. */
-	I915_CACHE_WT, /* hsw:gt3e WriteThrough for scanouts */
-};
 
 #define I915_COLOR_UNEVICTABLE (-1) /* a non-vma sharing the address space */
 
@@ -556,7 +609,7 @@ struct i915_gem_mm {
 	 * notifier_lock for mmu notifiers, memory may not be allocated
 	 * while holding this lock.
 	 */
-	spinlock_t notifier_lock;
+	rwlock_t notifier_lock;
 #endif
 
 	/* shrinker accounting, also useful for userland debugging */
@@ -1243,11 +1296,17 @@ static inline struct drm_i915_private *pdev_to_i915(struct pci_dev *pdev)
 
 #define INTEL_DEVID(dev_priv)	(RUNTIME_INFO(dev_priv)->device_id)
 
+#define IP_VER(ver, rel)              ((ver) << 8 | (rel))
+
 #define GRAPHICS_VER(i915)		(INTEL_INFO(i915)->graphics_ver)
+#define GRAPHICS_VER_FULL(i915)		IP_VER(INTEL_INFO(i915)->graphics_ver, \
+					       INTEL_INFO(i915)->graphics_rel)
 #define IS_GRAPHICS_VER(i915, from, until) \
 	(GRAPHICS_VER(i915) >= (from) && GRAPHICS_VER(i915) <= (until))
 
 #define MEDIA_VER(i915)			(INTEL_INFO(i915)->media_ver)
+#define MEDIA_VER_FULL(i915)		IP_VER(INTEL_INFO(i915)->media_ver, \
+					       INTEL_INFO(i915)->media_rel)
 #define IS_MEDIA_VER(i915, from, until) \
 	(MEDIA_VER(i915) >= (from) && MEDIA_VER(i915) <= (until))
 
@@ -1255,19 +1314,10 @@ static inline struct drm_i915_private *pdev_to_i915(struct pci_dev *pdev)
 #define IS_DISPLAY_VER(i915, from, until) \
 	(DISPLAY_VER(i915) >= (from) && DISPLAY_VER(i915) <= (until))
 
-#define REVID_FOREVER		0xff
 #define INTEL_REVID(dev_priv)	(to_pci_dev((dev_priv)->drm.dev)->revision)
 
 #define HAS_DSB(dev_priv)	(INTEL_INFO(dev_priv)->display.has_dsb)
 
-/*
- * Return true if revision is in range [since,until] inclusive.
- *
- * Use 0 for open-ended since, and REVID_FOREVER for open-ended until.
- */
-#define IS_REVID(p, since, until) \
-	(INTEL_REVID(p) >= (since) && INTEL_REVID(p) <= (until))
-
 #define INTEL_DISPLAY_STEP(__i915) (RUNTIME_INFO(__i915)->step.display_step)
 #define INTEL_GT_STEP(__i915) (RUNTIME_INFO(__i915)->step.gt_step)
 
@@ -1277,7 +1327,7 @@ static inline struct drm_i915_private *pdev_to_i915(struct pci_dev *pdev)
 
 #define IS_GT_STEP(__i915, since, until) \
 	(drm_WARN_ON(&(__i915)->drm, INTEL_GT_STEP(__i915) == STEP_NONE), \
-	 INTEL_GT_STEP(__i915) >= (since) && INTEL_GT_STEP(__i915) <= (until))
+	 INTEL_GT_STEP(__i915) >= (since) && INTEL_GT_STEP(__i915) < (until))
 
 static __always_inline unsigned int
 __platform_mask_index(const struct intel_runtime_info *info,
@@ -1385,6 +1435,12 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 #define IS_DG1(dev_priv)        IS_PLATFORM(dev_priv, INTEL_DG1)
 #define IS_ALDERLAKE_S(dev_priv) IS_PLATFORM(dev_priv, INTEL_ALDERLAKE_S)
 #define IS_ALDERLAKE_P(dev_priv) IS_PLATFORM(dev_priv, INTEL_ALDERLAKE_P)
+#define IS_XEHPSDV(dev_priv) IS_PLATFORM(dev_priv, INTEL_XEHPSDV)
+#define IS_DG2(dev_priv)	IS_PLATFORM(dev_priv, INTEL_DG2)
+#define IS_DG2_G10(dev_priv) \
+	IS_SUBPLATFORM(dev_priv, INTEL_DG2, INTEL_SUBPLATFORM_G10)
+#define IS_DG2_G11(dev_priv) \
+	IS_SUBPLATFORM(dev_priv, INTEL_DG2, INTEL_SUBPLATFORM_G11)
 #define IS_HSW_EARLY_SDV(dev_priv) (IS_HASWELL(dev_priv) && \
 				    (INTEL_DEVID(dev_priv) & 0xFF00) == 0x0C00)
 #define IS_BDW_ULT(dev_priv) \
@@ -1447,60 +1503,17 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 #define IS_TGL_Y(dev_priv) \
 	IS_SUBPLATFORM(dev_priv, INTEL_TIGERLAKE, INTEL_SUBPLATFORM_ULX)
 
-#define SKL_REVID_A0		0x0
-#define SKL_REVID_B0		0x1
-#define SKL_REVID_C0		0x2
-#define SKL_REVID_D0		0x3
-#define SKL_REVID_E0		0x4
-#define SKL_REVID_F0		0x5
-#define SKL_REVID_G0		0x6
-#define SKL_REVID_H0		0x7
-
-#define IS_SKL_REVID(p, since, until) (IS_SKYLAKE(p) && IS_REVID(p, since, until))
-
-#define BXT_REVID_A0		0x0
-#define BXT_REVID_A1		0x1
-#define BXT_REVID_B0		0x3
-#define BXT_REVID_B_LAST	0x8
-#define BXT_REVID_C0		0x9
-
-#define IS_BXT_REVID(dev_priv, since, until) \
-	(IS_BROXTON(dev_priv) && IS_REVID(dev_priv, since, until))
+#define IS_SKL_GT_STEP(p, since, until) (IS_SKYLAKE(p) && IS_GT_STEP(p, since, until))
 
 #define IS_KBL_GT_STEP(dev_priv, since, until) \
 	(IS_KABYLAKE(dev_priv) && IS_GT_STEP(dev_priv, since, until))
 #define IS_KBL_DISPLAY_STEP(dev_priv, since, until) \
 	(IS_KABYLAKE(dev_priv) && IS_DISPLAY_STEP(dev_priv, since, until))
 
-#define GLK_REVID_A0		0x0
-#define GLK_REVID_A1		0x1
-#define GLK_REVID_A2		0x2
-#define GLK_REVID_B0		0x3
-
-#define IS_GLK_REVID(dev_priv, since, until) \
-	(IS_GEMINILAKE(dev_priv) && IS_REVID(dev_priv, since, until))
-
-#define CNL_REVID_A0		0x0
-#define CNL_REVID_B0		0x1
-#define CNL_REVID_C0		0x2
-
-#define IS_CNL_REVID(p, since, until) \
-	(IS_CANNONLAKE(p) && IS_REVID(p, since, until))
-
-#define ICL_REVID_A0		0x0
-#define ICL_REVID_A2		0x1
-#define ICL_REVID_B0		0x3
-#define ICL_REVID_B2		0x4
-#define ICL_REVID_C0		0x5
-
-#define IS_ICL_REVID(p, since, until) \
-	(IS_ICELAKE(p) && IS_REVID(p, since, until))
-
-#define EHL_REVID_A0            0x0
-#define EHL_REVID_B0            0x1
-
-#define IS_JSL_EHL_REVID(p, since, until) \
-	(IS_JSL_EHL(p) && IS_REVID(p, since, until))
+#define IS_JSL_EHL_GT_STEP(p, since, until) \
+	(IS_JSL_EHL(p) && IS_GT_STEP(p, since, until))
+#define IS_JSL_EHL_DISPLAY_STEP(p, since, until) \
+	(IS_JSL_EHL(p) && IS_DISPLAY_STEP(p, since, until))
 
 #define IS_TGL_DISPLAY_STEP(__i915, since, until) \
 	(IS_TIGERLAKE(__i915) && \
@@ -1514,18 +1527,13 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 	(IS_TIGERLAKE(__i915) && !(IS_TGL_U(__i915) || IS_TGL_Y(__i915)) && \
 	 IS_GT_STEP(__i915, since, until))
 
-#define RKL_REVID_A0		0x0
-#define RKL_REVID_B0		0x1
-#define RKL_REVID_C0		0x4
-
-#define IS_RKL_REVID(p, since, until) \
-	(IS_ROCKETLAKE(p) && IS_REVID(p, since, until))
-
-#define DG1_REVID_A0		0x0
-#define DG1_REVID_B0		0x1
+#define IS_RKL_DISPLAY_STEP(p, since, until) \
+	(IS_ROCKETLAKE(p) && IS_DISPLAY_STEP(p, since, until))
 
-#define IS_DG1_REVID(p, since, until) \
-	(IS_DG1(p) && IS_REVID(p, since, until))
+#define IS_DG1_GT_STEP(p, since, until) \
+	(IS_DG1(p) && IS_GT_STEP(p, since, until))
+#define IS_DG1_DISPLAY_STEP(p, since, until) \
+	(IS_DG1(p) && IS_DISPLAY_STEP(p, since, until))
 
 #define IS_ADLS_DISPLAY_STEP(__i915, since, until) \
 	(IS_ALDERLAKE_S(__i915) && \
@@ -1543,6 +1551,31 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 	(IS_ALDERLAKE_P(__i915) && \
 	 IS_GT_STEP(__i915, since, until))
 
+#define IS_XEHPSDV_GT_STEP(__i915, since, until) \
+	(IS_XEHPSDV(__i915) && IS_GT_STEP(__i915, since, until))
+
+/*
+ * DG2 hardware steppings are a bit unusual.  The hardware design was forked
+ * to create two variants (G10 and G11) which have distinct workaround sets.
+ * The G11 fork of the DG2 design resets the GT stepping back to "A0" for its
+ * first iteration, even though it's more similar to a G10 B0 stepping in terms
+ * of functionality and workarounds.  However the display stepping does not
+ * reset in the same manner --- a specific stepping like "B0" has a consistent
+ * meaning regardless of whether it belongs to a G10 or G11 DG2.
+ *
+ * TLDR:  All GT workarounds and stepping-specific logic must be applied in
+ * relation to a specific subplatform (G10 or G11), whereas display workarounds
+ * and stepping-specific logic will be applied with a general DG2-wide stepping
+ * number.
+ */
+#define IS_DG2_GT_STEP(__i915, variant, since, until) \
+	(IS_SUBPLATFORM(__i915, INTEL_DG2, INTEL_SUBPLATFORM_##variant) && \
+	 IS_GT_STEP(__i915, since, until))
+
+#define IS_DG2_DISP_STEP(__i915, since, until) \
+	(IS_DG2(__i915) && \
+	 IS_DISPLAY_STEP(__i915, since, until))
+
 #define IS_LP(dev_priv)		(INTEL_INFO(dev_priv)->is_lp)
 #define IS_GEN9_LP(dev_priv)	(GRAPHICS_VER(dev_priv) == 9 && IS_LP(dev_priv))
 #define IS_GEN9_BC(dev_priv)	(GRAPHICS_VER(dev_priv) == 9 && !IS_LP(dev_priv))
@@ -1653,6 +1686,9 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 #define HAS_RUNTIME_PM(dev_priv) (INTEL_INFO(dev_priv)->has_runtime_pm)
 #define HAS_64BIT_RELOC(dev_priv) (INTEL_INFO(dev_priv)->has_64bit_reloc)
 
+#define HAS_MSLICES(dev_priv) \
+	(INTEL_INFO(dev_priv)->has_mslices)
+
 #define HAS_IPC(dev_priv)		 (INTEL_INFO(dev_priv)->display.has_ipc)
 
 #define HAS_REGION(i915, i) (INTEL_INFO(i915)->memory_regions & (i))
@@ -1742,9 +1778,6 @@ void i915_gem_cleanup_userptr(struct drm_i915_private *dev_priv);
 void i915_gem_init_early(struct drm_i915_private *dev_priv);
 void i915_gem_cleanup_early(struct drm_i915_private *dev_priv);
 
-struct intel_memory_region *i915_gem_shmem_setup(struct drm_i915_private *i915,
-						 u16 type, u16 instance);
-
 static inline void i915_gem_drain_freed_objects(struct drm_i915_private *i915)
 {
 	/*
@@ -1841,24 +1874,18 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 
 struct dma_buf *i915_gem_prime_export(struct drm_gem_object *gem_obj, int flags);
 
-static inline struct i915_gem_context *
-__i915_gem_context_lookup_rcu(struct drm_i915_file_private *file_priv, u32 id)
-{
-	return xa_load(&file_priv->context_xa, id);
-}
-
-static inline struct i915_gem_context *
-i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
+static inline struct i915_address_space *
+i915_gem_vm_lookup(struct drm_i915_file_private *file_priv, u32 id)
 {
-	struct i915_gem_context *ctx;
+	struct i915_address_space *vm;
 
 	rcu_read_lock();
-	ctx = __i915_gem_context_lookup_rcu(file_priv, id);
-	if (ctx && !kref_get_unless_zero(&ctx->ref))
-		ctx = NULL;
+	vm = xa_load(&file_priv->vm_xa, id);
+	if (vm && !kref_get_unless_zero(&vm->ref))
+		vm = NULL;
 	rcu_read_unlock();
 
-	return ctx;
+	return vm;
 }
 
 /* i915_gem_evict.c */
@@ -1925,8 +1952,8 @@ int remap_io_sg(struct vm_area_struct *vma,
 
 static inline int intel_hws_csb_write_index(struct drm_i915_private *i915)
 {
-	if (GRAPHICS_VER(i915) >= 10)
-		return CNL_HWS_CSB_WRITE_INDEX;
+	if (GRAPHICS_VER(i915) >= 11)
+		return ICL_HWS_CSB_WRITE_INDEX;
 	else
 		return I915_HWS_CSB_WRITE_INDEX;
 }