arch/tile: enhance existing finv_buffer_remote() routine

It now takes an additional argument so it can be used to
flush-and-invalidate pages that are cached using hash-for-home
as well those that are cached with coherence point on a single cpu.

This allows it to be used more widely for changing the coherence
point of arbitrary pages when necessary.

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

arch/tile/lib/cacheflush.c

@@ -21,3 +21,105 @@ void __flush_icache_range(unsigned long start, unsigned long end)
 {
 	invalidate_icache((const void *)start, end - start, PAGE_SIZE);
 }
+
+
+/* Force a load instruction to issue. */
+static inline void force_load(char *p)
+{
+	*(volatile char *)p;
+}
+
+/*
+ * Flush and invalidate a VA range that is homed remotely on a single
+ * core (if "!hfh") or homed via hash-for-home (if "hfh"), waiting
+ * until the memory controller holds the flushed values.
+ */
+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;
+
+	/*
+	 * Flush and invalidate the buffer out of the local L1/L2
+	 * and request the home cache to flush and invalidate as well.
+	 */
+	__finv_buffer(buffer, size);
+
+	/*
+	 * Wait for the home cache to acknowledge that it has processed
+	 * all the flush-and-invalidate requests.  This does not mean
+	 * that the flushed data has reached the memory controller yet,
+	 * but it does mean the home cache is processing the flushes.
+	 */
+	__insn_mf();
+
+	/*
+	 * Issue a load to the last cache line, which can't complete
+	 * until all the previously-issued flushes to the same memory
+	 * controller have also completed.  If we weren't striping
+	 * memory, that one load would be sufficient, but since we may
+	 * be, we also need to back up to the last load issued to
+	 * another memory controller, which would be the point where
+	 * we crossed an 8KB boundary (the granularity of striping
+	 * across memory controllers).  Keep backing up and doing this
+	 * until we are before the beginning of the buffer, or have
+	 * hit all the controllers.
+	 *
+	 * If we are flushing a hash-for-home buffer, it's even worse.
+	 * Each line may be homed on a different tile, and each tile
+	 * may have up to four lines that are on different
+	 * controllers.  So as we walk backwards, we have to touch
+	 * enough cache lines to satisfy these constraints.  In
+	 * practice this ends up being close enough to "load from
+	 * every cache line on a full memory stripe on each
+	 * controller" that we simply do that, to simplify the logic.
+	 *
+	 * FIXME: See bug 9535 for some issues with this code.
+	 */
+	if (hfh) {
+		step_size = L2_CACHE_BYTES;
+		load_count = (STRIPE_WIDTH / L2_CACHE_BYTES) *
+			      (1 << CHIP_LOG_NUM_MSHIMS());
+	} else {
+		step_size = STRIPE_WIDTH;
+		load_count = (1 << CHIP_LOG_NUM_MSHIMS());
+	}
+
+	/* Load the last byte of the buffer. */
+	p = (char *)buffer + size - 1;
+	force_load(p);
+
+	/* Bump down to the end of the previous stripe or cache line. */
+	p -= step_size;
+	p = (char *)((unsigned long)p | (step_size - 1));
+
+	/* Figure out how far back we need to go. */
+	base = p - (step_size * (load_count - 2));
+	if ((long)base < (long)buffer)
+		base = buffer;
+
+	/*
+	 * Fire all the loads we need.  The MAF only has eight entries
+	 * so we can have at most eight outstanding loads, so we
+	 * unroll by that amount.
+	 */
+#pragma unroll 8
+	for (; p >= base; p -= step_size)
+		force_load(p);
+
+	/*
+	 * Repeat, but with inv's instead of loads, to get rid of the
+	 * data we just loaded into our own cache and the old home L3.
+	 * No need to unroll since inv's don't target a register.
+	 */
+	p = (char *)buffer + size - 1;
+	__insn_inv(p);
+	p -= step_size;
+	p = (char *)((unsigned long)p | (step_size - 1));
+	for (; p >= base; p -= step_size)
+		__insn_inv(p);
+
+	/* Wait for the load+inv's (and thus finvs) to have completed. */
+	__insn_mf();
+}