drm/i915: Implement read-only support in whitelist selftest

Newer hardware supports extra feature in the whitelist registers. This
patch updates the selftest to test that entries marked as read only
are actually read only.

v2: Removed all use of 'rsvd' for read-only registers to avoid
ambiguous code or error messages.
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
CC: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712070745.35239-3-John.C.Harrison@Intel.com

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

@@ -485,12 +485,12 @@ static int check_dirty_whitelist(struct i915_gem_context *ctx,
 		u32 srm, lrm, rsvd;
 		u32 expect;
 		int idx;
+		bool ro_reg;
 
 		if (wo_register(engine, reg))
 			continue;
 
-		if (ro_register(reg))
-			continue;
+		ro_reg = ro_register(reg);
 
 		srm = MI_STORE_REGISTER_MEM;
 		lrm = MI_LOAD_REGISTER_MEM;
@@ -591,24 +591,35 @@ static int check_dirty_whitelist(struct i915_gem_context *ctx,
 		}
 
 		GEM_BUG_ON(values[ARRAY_SIZE(values) - 1] != 0xffffffff);
-		rsvd = results[ARRAY_SIZE(values)]; /* detect write masking */
-		if (!rsvd) {
-			pr_err("%s: Unable to write to whitelisted register %x\n",
-			       engine->name, reg);
-			err = -EINVAL;
-			goto out_unpin;
+		if (!ro_reg) {
+			/* detect write masking */
+			rsvd = results[ARRAY_SIZE(values)];
+			if (!rsvd) {
+				pr_err("%s: Unable to write to whitelisted register %x\n",
+				       engine->name, reg);
+				err = -EINVAL;
+				goto out_unpin;
+			}
 		}
 
 		expect = results[0];
 		idx = 1;
 		for (v = 0; v < ARRAY_SIZE(values); v++) {
-			expect = reg_write(expect, values[v], rsvd);
+			if (ro_reg)
+				expect = results[0];
+			else
+				expect = reg_write(expect, values[v], rsvd);
+
 			if (results[idx] != expect)
 				err++;
 			idx++;
 		}
 		for (v = 0; v < ARRAY_SIZE(values); v++) {
-			expect = reg_write(expect, ~values[v], rsvd);
+			if (ro_reg)
+				expect = results[0];
+			else
+				expect = reg_write(expect, ~values[v], rsvd);
+
 			if (results[idx] != expect)
 				err++;
 			idx++;
@@ -617,15 +628,22 @@ static int check_dirty_whitelist(struct i915_gem_context *ctx,
 			pr_err("%s: %d mismatch between values written to whitelisted register [%x], and values read back!\n",
 			       engine->name, err, reg);
 
-			pr_info("%s: Whitelisted register: %x, original value %08x, rsvd %08x\n",
-				engine->name, reg, results[0], rsvd);
+			if (ro_reg)
+				pr_info("%s: Whitelisted read-only register: %x, original value %08x\n",
+					engine->name, reg, results[0]);
+			else
+				pr_info("%s: Whitelisted register: %x, original value %08x, rsvd %08x\n",
+					engine->name, reg, results[0], rsvd);
 
 			expect = results[0];
 			idx = 1;
 			for (v = 0; v < ARRAY_SIZE(values); v++) {
 				u32 w = values[v];
 
-				expect = reg_write(expect, w, rsvd);
+				if (ro_reg)
+					expect = results[0];
+				else
+					expect = reg_write(expect, w, rsvd);
 				pr_info("Wrote %08x, read %08x, expect %08x\n",
 					w, results[idx], expect);
 				idx++;
@@ -633,7 +651,10 @@ static int check_dirty_whitelist(struct i915_gem_context *ctx,
 			for (v = 0; v < ARRAY_SIZE(values); v++) {
 				u32 w = ~values[v];
 
-				expect = reg_write(expect, w, rsvd);
+				if (ro_reg)
+					expect = results[0];
+				else
+					expect = reg_write(expect, w, rsvd);
 				pr_info("Wrote %08x, read %08x, expect %08x\n",
 					w, results[idx], expect);
 				idx++;