b43: Disable PMQ mechanism

This reduces IRQ pressure by about one third on a saturated link
by disabling the PMQ mechanism. We currently don't use that mechanism.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/main.c

@@ -2675,6 +2675,20 @@ static void b43_adjust_opmode(struct b43_wldev *dev)
 			cfp_pretbtt = 50;
 	}
 	b43_write16(dev, 0x612, cfp_pretbtt);
+
+	/* FIXME: We don't currently implement the PMQ mechanism,
+	 *        so always disable it. If we want to implement PMQ,
+	 *        we need to enable it here (clear DISCPMQ) in AP mode.
+	 */
+	if (0  /* ctl & B43_MACCTL_AP */) {
+		b43_write32(dev, B43_MMIO_MACCTL,
+			    b43_read32(dev, B43_MMIO_MACCTL)
+			    & ~B43_MACCTL_DISCPMQ);
+	} else {
+		b43_write32(dev, B43_MMIO_MACCTL,
+			    b43_read32(dev, B43_MMIO_MACCTL)
+			    | B43_MACCTL_DISCPMQ);
+	}
 }
 
 static void b43_rate_memory_write(struct b43_wldev *dev, u16 rate, int is_ofdm)