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Subject[PATCH 04/10] powerpc/vas: Drop poll_window_cast_out().
Date
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>
---
arch/powerpc/platforms/powernv/vas-window.c | 34 ++++++++++++++---------------
1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 67ffc5d..8ab8a82 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -1079,25 +1079,25 @@ static void poll_window_busy_state(struct vas_window *window)
}
}

+/*
+ * 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 */
}

/*
--
2.7.4
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