powerpc/vas: Drop poll_window_cast_out().

Polling for window cast out is listed in the spec, but turns out that
it is not strictly necessary and slows down window close. Making it a
stub for now.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 67ffc5d..8ab8a82 100644 (file)
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -1079,25 +1079,25 @@ retry:
        }
 }
 
+/*
+ * Have the hardware cast a window out of cache and wait for it to
+ * be completed.
+ *
+ * NOTE: It can take a relatively long time to cast the window context
+ *     out of the cache. It is not strictly necessary to cast out if:
+ *
+ *     - we clear the "Pin Window" bit (so hardware is free to evict)
+ *
+ *     - we re-initialize the window context when it is reassigned.
+ *
+ *     We do the former in vas_win_close() and latter in vas_win_open().
+ *     So, ignoring the cast-out for now. We can add it as needed. If
+ *     casting out becomes necessary we should consider offloading the
+ *     job to a worker thread, so the window close can proceed quickly.
+ */
 static void poll_window_castout(struct vas_window *window)
 {
-       int cached;
-       u64 val;
-
-       /* Cast window context out of the cache */
-retry:
-       val = read_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL));
-       cached = GET_FIELD(VAS_WIN_CACHE_STATUS, val);
-       if (cached) {
-               val = 0ULL;
-               val = SET_FIELD(VAS_CASTOUT_REQ, val, 1);
-               val = SET_FIELD(VAS_PUSH_TO_MEM, val, 0);
-               write_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL), val);
-
-               set_current_state(TASK_UNINTERRUPTIBLE);
-               schedule_timeout(HZ);
-               goto retry;
-       }
+       /* stub for now */
 }
 
 /*