drm/i915: Disable atomics in L3 for gen9

Enabling atomic operations in L3 leads to unrecoverable GPU hangs, as
the machine stops responding milliseconds after receipt of the reset
request [GDRT]. By disabling the cached atomics, the hang do not occur
and we presume the GPU would reset normally for similar hangs.

Sadly this is a shotgun approach, but since the impact is critical it is
better to err on the safe side and work back from there.

Reported-by: Jason Ekstrand <jason@jlekstrand.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110998
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Jason Ekstrand <jason@jlesktrand.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210125220152.24070-1-chris@chris-wilson.co.uk
Cc: stable@vger.kernel.org
(cherry picked from commit b267c7a)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

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

@@ -1834,6 +1834,14 @@ rcs_engine_wa_init(struct intel_engine_cs *engine, struct i915_wa_list *wal)
 		wa_write_or(wal,
 			    GEN8_L3SQCREG4,
 			    GEN8_LQSC_FLUSH_COHERENT_LINES);
+
+		/* Disable atomics in L3 to prevent unrecoverable hangs */
+		wa_write_clr_set(wal, GEN9_SCRATCH_LNCF1,
+				 GEN9_LNCF_NONIA_COHERENT_ATOMICS_ENABLE, 0);
+		wa_write_clr_set(wal, GEN8_L3SQCREG4,
+				 GEN8_LQSQ_NONIA_COHERENT_ATOMICS_ENABLE, 0);
+		wa_write_clr_set(wal, GEN9_SCRATCH1,
+				 EVICTION_PERF_FIX_ENABLE, 0);
 	}
 
 	if (IS_HASWELL(i915)) {

drivers/gpu/drm/i915/i915_reg.h

@@ -8225,6 +8225,7 @@ enum {
 #define  GEN11_LQSC_CLEAN_EVICT_DISABLE		(1 << 6)
 #define  GEN8_LQSC_RO_PERF_DIS			(1 << 27)
 #define  GEN8_LQSC_FLUSH_COHERENT_LINES		(1 << 21)
+#define  GEN8_LQSQ_NONIA_COHERENT_ATOMICS_ENABLE REG_BIT(22)
 
 /* GEN8 chicken */
 #define HDC_CHICKEN0				_MMIO(0x7300)
@@ -12107,6 +12108,12 @@ enum skl_power_gate {
 #define __GEN11_VCS2_MOCS0	0x10000
 #define GEN11_MFX2_MOCS(i)	_MMIO(__GEN11_VCS2_MOCS0 + (i) * 4)
 
+#define GEN9_SCRATCH_LNCF1		_MMIO(0xb008)
+#define   GEN9_LNCF_NONIA_COHERENT_ATOMICS_ENABLE REG_BIT(0)
+
+#define GEN9_SCRATCH1			_MMIO(0xb11c)
+#define   EVICTION_PERF_FIX_ENABLE	REG_BIT(8)
+
 #define GEN10_SCRATCH_LNCF2		_MMIO(0xb0a0)
 #define   PMFLUSHDONE_LNICRSDROP	(1 << 20)
 #define   PMFLUSH_GAPL3UNBLOCK		(1 << 21)