sunxi: mmc: increase status register polling rate for data transfers

With a recent bunch of SD3.0 cards in our A20-based board we
experienced data transfer rates of about 250 KiB/s instead of 10 MiB/s
with previous cards from the same vendor (both 4 GB/class 10). By
increasing status register polling rate from 1 kHz to 1 MHz we were
able to reach the original transfer rates again. With the old cards
we now even reach about 16 MiB/s.

Signed-off-by: Tobias Doerffel <tobias.doerffel@ed-chemnitz.de>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/mmc/sunxi_mmc.c

@@ -269,18 +269,18 @@ static int mmc_trans_data_by_cpu(struct mmc *mmc, struct mmc_data *data)
 	unsigned i;
 	unsigned *buff = (unsigned int *)(reading ? data->dest : data->src);
 	unsigned byte_cnt = data->blocksize * data->blocks;
-	unsigned timeout_msecs = byte_cnt >> 8;
-	if (timeout_msecs < 2000)
-		timeout_msecs = 2000;
+	unsigned timeout_usecs = (byte_cnt >> 8) * 1000;
+	if (timeout_usecs < 2000000)
+		timeout_usecs = 2000000;
 
 	/* Always read / write data through the CPU */
 	setbits_le32(&mmchost->reg->gctrl, SUNXI_MMC_GCTRL_ACCESS_BY_AHB);
 
 	for (i = 0; i < (byte_cnt >> 2); i++) {
 		while (readl(&mmchost->reg->status) & status_bit) {
-			if (!timeout_msecs--)
+			if (!timeout_usecs--)
 				return -1;
-			udelay(1000);
+			udelay(1);
 		}
 
 		if (reading)