[Skiboot] [PATCH 20/32] xive: Add cache scrub to push watch updates to memory

[Benjamin Herrenschmidt]

We use the cache watch to write to some structures that we sometimes
want to read back using normal loads. The cache watch facility only
writes to the cache though, we need to add a non-invalidating cache
scrub to also push the result to memory.

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
 hw/xive.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/hw/xive.c b/hw/xive.c
index ad01b52..f596dba 100644
--- a/hw/xive.c
+++ b/hw/xive.c
@@ -807,13 +807,15 @@ static int64_t __xive_cache_scrub(struct xive *x, enum xive_cache_type ctype,
 		sval = __xive_regr(x, sreg, sregx, NULL);
 		if (!(sval & VC_SCRUB_VALID))
 			break;
-		time_wait_us(1);
+		/* Small delay */
+		time_wait(100);
 	}
 	return 0;
 }
 
 static int64_t xive_ivc_scrub(struct xive *x, uint64_t block, uint64_t idx)
 {
+	/* IVC has no "want_inval" bit, it always invalidates */
 	return __xive_cache_scrub(x, xive_cache_ivc, block, idx, false, false);
 }
 
@@ -849,7 +851,7 @@ static int64_t __xive_cache_watch(struct xive *x, enum xive_cache_type ctype,
 	if (!light_watch)
 		sval |= VC_EQC_CWATCH_FULL;
 
-	do {
+	for (;;) {
 		/* Write the cache watch spec */
 		__xive_regw(x, sreg, sregx, sval, NULL);
 
@@ -871,21 +873,25 @@ static int64_t __xive_cache_watch(struct xive *x, enum xive_cache_type ctype,
 		if (start_dword > 0)
 			__xive_regw(x, dreg0, dreg0x, dval0, NULL);
 
-		/* This may not be necessary for light updates (it's possible\
+		/* This may not be necessary for light updates (it's possible
 		 * that a sync in sufficient, TBD). Ensure the above is
 		 * complete and check the status of the watch.
 		 */
 		status = __xive_regr(x, sreg, sregx, NULL);
 
-		/* XXX Add timeout ? */
-
 		/* Bits FULL and CONFLICT are in the same position in
 		 * EQC and VPC
 		 */
-	} while((status & VC_EQC_CWATCH_FULL) &&
-		(status & VC_EQC_CWATCH_CONFLICT));
+		if (!(status & VC_EQC_CWATCH_FULL) ||
+		    !(status & VC_EQC_CWATCH_CONFLICT))
+			break;
+		/* XXX Add timeout ? */
+	}
 
-	return 0;
+	/* Perform a scrub with "want_invalidate" set to false to push the
+	 * cache updates to memory as well
+	 */
+	return __xive_cache_scrub(x, ctype, block, idx, false, false);
 }
 
 static int64_t xive_eqc_cache_update(struct xive *x, uint64_t block,
-- 
2.7.4