arch/tile: disable GX prefetcher during cache flush

Otherwise, it's possible to end up with the prefetcher pulling
data into cache that the code believes has been flushed.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/tile/lib/cacheflush.c b/arch/tile/lib/cacheflush.c
index 35c1d8ca5f38..8928aace7a64 100644
--- a/arch/tile/lib/cacheflush.c
+++ b/arch/tile/lib/cacheflush.c
@@ -15,6 +15,7 @@
 #include <asm/page.h>
 #include <asm/cacheflush.h>
 #include <arch/icache.h>
+#include <arch/spr_def.h>
 
 
 void __flush_icache_range(unsigned long start, unsigned long end)
@@ -39,6 +40,18 @@ void finv_buffer_remote(void *buffer, size_t size, int hfh)
         char *p, *base;
         size_t step_size, load_count;
         const unsigned long STRIPE_WIDTH = 8192;
+#ifdef __tilegx__
+        /*
+         * On TILE-Gx, we must disable the dstream prefetcher before doing
+         * a cache flush; otherwise, we could end up with data in the cache
+         * that we don't want there.  Note that normally we'd do an mf
+         * after the SPR write to disabling the prefetcher, but we do one
+         * below, before any further loads, so there's no need to do it
+         * here.
+         */
+        uint_reg_t old_dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
+        __insn_mtspr(SPR_DSTREAM_PF, 0);
+#endif
 
         /*
          * Flush and invalidate the buffer out of the local L1/L2
@@ -122,4 +135,9 @@ void finv_buffer_remote(void *buffer, size_t size, int hfh)
 
         /* Wait for the load+inv's (and thus finvs) to have completed. */
         __insn_mf();
+
+#ifdef __tilegx__
+        /* Reenable the prefetcher. */
+        __insn_mtspr(SPR_DSTREAM_PF, old_dstream_pf);
+#endif
 }