sdhci-bcm2708: use multiblock-type transfers for single blocks

There are issues with both single block reads (missed completion)
and writes (data loss in some cases!). Just don't do single block
transfers anymore, and treat them like multiblock transfers. This
adds a quirk for this and uses it.

drivers/mmc/card/block.c

@@ -965,7 +965,7 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,
 	if (disable_multi && brq->data.blocks > 1)
 		brq->data.blocks = 1;
 
-	if (brq->data.blocks > 1 || do_rel_wr) {
+	if (brq->data.blocks > 1 || do_rel_wr || card->host->caps2 & MMC_CAP2_FORCE_MULTIBLOCK) {
 		/* SPI multiblock writes terminate using a special
 		 * token, not a STOP_TRANSMISSION request.
 		 */

drivers/mmc/host/sdhci-bcm2708.c

@@ -1392,6 +1392,9 @@ static int __devinit sdhci_bcm2708_probe(struct platform_device *pdev)
 
     if (allow_highspeed)
         host->mmc->caps |= MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED;
+
+    /* single block writes cause data loss with some SD cards! */
+    host->mmc->caps2 |= MMC_CAP2_FORCE_MULTIBLOCK;
 #endif
 
 	ret = sdhci_add_host(host);

include/linux/mmc/host.h

@@ -242,6 +242,7 @@ struct mmc_host {
 #define MMC_CAP2_CACHE_CTRL	(1 << 1)	/* Allow cache control */
 #define MMC_CAP2_POWEROFF_NOTIFY (1 << 2)	/* Notify poweroff supported */
 #define MMC_CAP2_NO_MULTI_READ	(1 << 3)	/* Multiblock reads don't work */
+#define MMC_CAP2_FORCE_MULTIBLOCK (1 << 4)	/* Always use multiblock transfers */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */
 	unsigned int        power_notify_type;