drm/nv50/gr: enable ctxprog xfer only when we need it to save power
This patch adds instructions to ctxprog and by doing, impacts context
switching performance. My testcase showed a 1% performance cost using
glxgears that is a context-switch bound application.
Please test and report bugs/performance/power/other.
Many thanks to Maxim Levitsky for his dedicated work on lowering power
consumption with nouveau.
More patches are coming thanks to his work:
https://bugs.freedesktop.org/show_bug.cgi?id=37922
Signed-off-by: Martin Peres <martin.peres@ensi-bourges.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nv50_grctx.c b/drivers/gpu/drm/nouveau/nv50_grctx.c
index e04fb44..d05c2c3 100644
--- a/drivers/gpu/drm/nouveau/nv50_grctx.c
+++ b/drivers/gpu/drm/nouveau/nv50_grctx.c
@@ -40,6 +40,9 @@
#define CP_FLAG_UNK0B ((0 * 32) + 0xb)
#define CP_FLAG_UNK0B_CLEAR 0
#define CP_FLAG_UNK0B_SET 1
+#define CP_FLAG_XFER_SWITCH ((0 * 32) + 0xe)
+#define CP_FLAG_XFER_SWITCH_DISABLE 0
+#define CP_FLAG_XFER_SWITCH_ENABLE 1
#define CP_FLAG_STATE ((0 * 32) + 0x1c)
#define CP_FLAG_STATE_STOPPED 0
#define CP_FLAG_STATE_RUNNING 1
@@ -199,6 +202,7 @@
}
cp_set (ctx, STATE, RUNNING);
+ cp_set (ctx, XFER_SWITCH, ENABLE);
/* decide whether we're loading/unloading the context */
cp_bra (ctx, AUTO_SAVE, PENDING, cp_setup_save);
cp_bra (ctx, USER_SAVE, PENDING, cp_setup_save);
@@ -265,6 +269,7 @@
cp_name(ctx, cp_exit);
cp_set (ctx, USER_SAVE, NOT_PENDING);
cp_set (ctx, USER_LOAD, NOT_PENDING);
+ cp_set (ctx, XFER_SWITCH, DISABLE);
cp_set (ctx, STATE, STOPPED);
cp_out (ctx, CP_END);
ctx->ctxvals_pos += 0x400; /* padding... no idea why you need it */