xilinx_spips: lqspi: Push more data to tx-fifo

Do 16 words per fifo flush. Increases performance and decreases
debug verbosity. This data depth has no real hardware analogue,
so just go with something that has reasonable performance.
Signed-off-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NEdgar E. Iglesias <edgar.iglesias@gmail.com>
Message-id: 5621ee4621941d3639b5cacfdec26bd3148f31d5.1369117359.git.peter.crosthwaite@xilinx.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/ssi/xilinx_spips.c

@@ -608,11 +608,14 @@ lqspi_read(void *opaque, hwaddr addr, unsigned int size)
 
         DB_PRINT_L(0, "starting QSPI data read\n");
 
-        for (i = 0; i < LQSPI_CACHE_SIZE / 4; ++i) {
-            tx_data_bytes(s, 0, 4);
+        while (cache_entry < LQSPI_CACHE_SIZE / 4) {
+            for (i = 0; i < 16; ++i) {
+                tx_data_bytes(s, 0, 4);
+            }
             xilinx_spips_flush_txfifo(s);
-            rx_data_bytes(s, &q->lqspi_buf[cache_entry], 4);
-            cache_entry++;
+            for (i = 0; i < 16; ++i) {
+                rx_data_bytes(s, &q->lqspi_buf[cache_entry++], 4);
+            }
         }
 
         s->regs[R_LQSPI_STS] &= ~LQSPI_CFG_U_PAGE;