sh: Fix problems with cache flushing when cache is in write-through mode
Change the method used to flush the cache in write-through mode to
avoid corrupted data being written back to memory.
Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/mm/cache-sh4.c b/arch/sh/mm/cache-sh4.c
index 7ce8161..397c103 100644
--- a/arch/sh/mm/cache-sh4.c
+++ b/arch/sh/mm/cache-sh4.c
@@ -592,6 +592,20 @@
* this with a cache invalidate to mark the cache line invalid. And do all
* this with interrupts disabled, to avoid the cache line being accidently
* evicted while it is holding garbage.
+ *
+ * This also breaks in a number of circumstances:
+ * - if there are modifications to the region of memory just above
+ * empty_zero_page (for example because a breakpoint has been placed
+ * there), then these can be lost.
+ *
+ * This is because the the memory address which the cache temporarily
+ * caches in the above description is empty_zero_page. So the
+ * movca.l hits the cache (it is assumed that it misses, or at least
+ * isn't dirty), modifies the line and then invalidates it, losing the
+ * required change.
+ *
+ * - If caches are disabled or configured in write-through mode, then
+ * the movca.l writes garbage directly into memory.
*/
static void __flush_dcache_segment_1way(unsigned long start,
unsigned long extent_per_way)
@@ -641,6 +655,25 @@
} while (a0 < a0e);
}
+#ifdef CONFIG_CACHE_WRITETHROUGH
+/* This method of cache flushing avoids the problems discussed
+ * in the comment above if writethrough caches are enabled. */
+static void __flush_dcache_segment_2way(unsigned long start,
+ unsigned long extent_per_way)
+{
+ unsigned long array_addr;
+
+ array_addr = CACHE_OC_ADDRESS_ARRAY |
+ (start & cpu_data->dcache.entry_mask);
+
+ while (extent_per_way) {
+ ctrl_outl(0, array_addr);
+ ctrl_outl(0, array_addr + cpu_data->dcache.way_incr);
+ array_addr += cpu_data->dcache.linesz;
+ extent_per_way -= cpu_data->dcache.linesz;
+ }
+}
+#else
static void __flush_dcache_segment_2way(unsigned long start,
unsigned long extent_per_way)
{
@@ -699,6 +732,7 @@
a1 += linesz;
} while (a0 < a0e);
}
+#endif
static void __flush_dcache_segment_4way(unsigned long start,
unsigned long extent_per_way)