mmc: mxcmmc: fix SD cards not being detected sometimes.

When a SD card is initialized some data transfers of 64 and 8 bytes
are issued. It seems the DMA has some problems dealing with these kind
of "short" transfers, leading sometimes to the SD card not being detected.

In order to solve this problem, do not use DMA for transfer sizes lower
than the sector size.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

diff --git a/drivers/mmc/host/mxcmmc.c b/drivers/mmc/host/mxcmmc.c
index 6290b7f1ccfec2d56f31675663923e057a1570c8..29e680f193a0a44bce9abd723e5b23c9758df402 100644 (file)
--- a/drivers/mmc/host/mxcmmc.c
+++ b/drivers/mmc/host/mxcmmc.c
@@ -240,7 +240,7 @@ static int mxcmci_setup_data(struct mxcmci_host *host, struct mmc_data *data)
                return 0;
 
        for_each_sg(data->sg, sg, data->sg_len, i) {
-               if (sg->offset & 3 || sg->length & 3) {
+               if (sg->offset & 3 || sg->length & 3 || sg->length < 512) {
                        host->do_dma = 0;
                        return 0;
                }