drm/i915: Fix application of WaInPlaceDecompressionHang

On SKL we've been applying this workaround on H0+ steppings, which is
actually backwards; H0 is supposed to be the first stepping where the
workaround is no longer needed.  Flip the bounds so that the workaround
applies to all steppings _before_ H0.

On BXT we've been applying this workaround to all steppings, but the
bspec tells us it's only needed until C0.  Pre-C0 GT steppings only
appeared in pre-production hardware, which we no longer support in the
driver, so we can drop the workaround completely for this platform.

On ICL we've been applying this workaround to all steppings, but there
doesn't seem to be any indication that this workaround was ever needed
for this platform (even now-deprecated page 20196 of the bspec doesn't
mention it).  We can go ahead and drop it.

I also don't see any mention of this workaround being needed for KBL,
although this may be an oversight since the workaround is needed for all
steppings of CFL.  I'll leave the workaround in place for KBL to be
safe.

Bspec: 14091, 33450
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210717051426.4120328-2-matthew.d.roper@intel.com

drivers/gpu/drm/i915/gt/intel_workarounds.c

@@ -838,18 +838,7 @@ skl_gt_workarounds_init(struct drm_i915_private *i915, struct i915_wa_list *wal)
 		    GEN8_EU_GAUNIT_CLOCK_GATE_DISABLE);
 
 	/* WaInPlaceDecompressionHang:skl */
-	if (IS_SKL_GT_STEP(i915, STEP_H0, STEP_FOREVER))
-		wa_write_or(wal,
-			    GEN9_GAMT_ECO_REG_RW_IA,
-			    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
-}
-
-static void
-bxt_gt_workarounds_init(struct drm_i915_private *i915, struct i915_wa_list *wal)
-{
-	gen9_gt_workarounds_init(i915, wal);
-
-	/* WaInPlaceDecompressionHang:bxt */
+	if (IS_SKL_GT_STEP(i915, STEP_A0, STEP_H0 - 1))
 		wa_write_or(wal,
 			    GEN9_GAMT_ECO_REG_RW_IA,
 			    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
@@ -942,11 +931,6 @@ icl_gt_workarounds_init(struct drm_i915_private *i915, struct i915_wa_list *wal)
 {
 	icl_wa_init_mcr(i915, wal);
 
-	/* WaInPlaceDecompressionHang:icl */
-	wa_write_or(wal,
-		    GEN9_GAMT_ECO_REG_RW_IA,
-		    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
-
 	/* WaModifyGamTlbPartitioning:icl */
 	wa_write_clr_set(wal,
 			 GEN11_GACB_PERF_CTRL,
@@ -1081,7 +1065,7 @@ gt_init_workarounds(struct drm_i915_private *i915, struct i915_wa_list *wal)
 	else if (IS_KABYLAKE(i915))
 		kbl_gt_workarounds_init(i915, wal);
 	else if (IS_BROXTON(i915))
-		bxt_gt_workarounds_init(i915, wal);
+		gen9_gt_workarounds_init(i915, wal);
 	else if (IS_SKYLAKE(i915))
 		skl_gt_workarounds_init(i915, wal);
 	else if (IS_HASWELL(i915))