mmc: remove multiwrite capability

Relax requirements on host controllers and only require that they do not
report a transfer count than is larger than the actual one (i.e. a lower
value is okay). This is how many other parts of the kernel behaves so
upper layers should already be prepared to handle that scenario. This
gives us a performance boost on MMC cards.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/card/block.c

@@ -237,17 +237,6 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 		if (brq.data.blocks > card->host->max_blk_count)
 			brq.data.blocks = card->host->max_blk_count;
 
-		/*
-		 * If the host doesn't support multiple block writes, force
-		 * block writes to single block. SD cards are excepted from
-		 * this rule as they support querying the number of
-		 * successfully written sectors.
-		 */
-		if (rq_data_dir(req) != READ &&
-		    !(card->host->caps & MMC_CAP_MULTIWRITE) &&
-		    !mmc_card_sd(card))
-			brq.data.blocks = 1;
-
 		if (brq.data.blocks > 1) {
 			/* SPI multiblock writes terminate using a special
 			 * token, not a STOP_TRANSMISSION request.
@@ -367,12 +356,14 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
  	 * mark the known good sectors as ok.
  	 *
 	 * If the card is not SD, we can still ok written sectors
-	 * if the controller can do proper error reporting.
+	 * as reported by the controller (which might be less than
+	 * the real number of written sectors, but never more).
 	 *
 	 * For reads we just fail the entire chunk as that should
 	 * be safe in all cases.
 	 */
- 	if (rq_data_dir(req) != READ && mmc_card_sd(card)) {
+	if (rq_data_dir(req) != READ) {
+		if (mmc_card_sd(card)) {
 			u32 blocks;
 			unsigned int bytes;
 
@@ -386,12 +377,12 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 				ret = __blk_end_request(req, 0, bytes);
 				spin_unlock_irq(&md->lock);
 			}
-	} else if (rq_data_dir(req) != READ &&
-		   (card->host->caps & MMC_CAP_MULTIWRITE)) {
+		} else {
 			spin_lock_irq(&md->lock);
 			ret = __blk_end_request(req, 0, brq.data.bytes_xfered);
 			spin_unlock_irq(&md->lock);
 		}
+	}
 
 	mmc_release_host(card->host);
 

drivers/mmc/host/at91_mci.c

@@ -995,7 +995,7 @@ static int __init at91_mci_probe(struct platform_device *pdev)
 	mmc->f_min = 375000;
 	mmc->f_max = 25000000;
 	mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
-	mmc->caps = MMC_CAP_MULTIWRITE | MMC_CAP_SDIO_IRQ;
+	mmc->caps = MMC_CAP_SDIO_IRQ;
 
 	mmc->max_blk_size = 4095;
 	mmc->max_blk_count = mmc->max_req_size;

drivers/mmc/host/atmel-mci.c

@@ -849,7 +849,7 @@ static int __init atmci_probe(struct platform_device *pdev)
 	mmc->f_min = (host->bus_hz + 511) / 512;
 	mmc->f_max = host->bus_hz / 2;
 	mmc->ocr_avail	= MMC_VDD_32_33 | MMC_VDD_33_34;
-	mmc->caps |= MMC_CAP_4_BIT_DATA | MMC_CAP_MULTIWRITE;
+	mmc->caps |= MMC_CAP_4_BIT_DATA;
 
 	mmc->max_hw_segs = 64;
 	mmc->max_phys_segs = 64;

drivers/mmc/host/mmc_spi.c

@@ -1252,10 +1252,7 @@ static int mmc_spi_probe(struct spi_device *spi)
 	mmc->ops = &mmc_spi_ops;
 	mmc->max_blk_size = MMC_SPI_BLOCKSIZE;
 
-	/* As long as we keep track of the number of successfully
-	 * transmitted blocks, we're good for multiwrite.
-	 */
-	mmc->caps = MMC_CAP_SPI | MMC_CAP_MULTIWRITE;
+	mmc->caps = MMC_CAP_SPI;
 
 	/* SPI doesn't need the lowspeed device identification thing for
 	 * MMC or SD cards, since it never comes up in open drain mode.

drivers/mmc/host/mmci.c

@@ -535,7 +535,6 @@ static int mmci_probe(struct amba_device *dev, void *id)
 	mmc->f_min = (host->mclk + 511) / 512;
 	mmc->f_max = min(host->mclk, fmax);
 	mmc->ocr_avail = plat->ocr_mask;
-	mmc->caps = MMC_CAP_MULTIWRITE;
 
 	/*
 	 * We can do SGIO

drivers/mmc/host/omap.c

@@ -1317,7 +1317,7 @@ static int __init mmc_omap_new_slot(struct mmc_omap_host *host, int id)
 
 	host->slots[id] = slot;
 
-	mmc->caps = MMC_CAP_MULTIWRITE;
+	mmc->caps = 0;
 	if (host->pdata->conf.wire4)
 		mmc->caps |= MMC_CAP_4_BIT_DATA;
 

drivers/mmc/host/tifm_sd.c

@@ -973,7 +973,7 @@ static int tifm_sd_probe(struct tifm_dev *sock)
 
 	mmc->ops = &tifm_sd_ops;
 	mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
-	mmc->caps = MMC_CAP_4_BIT_DATA | MMC_CAP_MULTIWRITE;
+	mmc->caps = MMC_CAP_4_BIT_DATA;
 	mmc->f_min = 20000000 / 60;
 	mmc->f_max = 24000000;
 

drivers/mmc/host/wbsd.c

@@ -1219,7 +1219,7 @@ static int __devinit wbsd_alloc_mmc(struct device *dev)
 	mmc->f_min = 375000;
 	mmc->f_max = 24000000;
 	mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
-	mmc->caps = MMC_CAP_4_BIT_DATA | MMC_CAP_MULTIWRITE;
+	mmc->caps = MMC_CAP_4_BIT_DATA;
 
 	spin_lock_init(&host->lock);
 

include/linux/mmc/host.h

@@ -111,12 +111,11 @@ struct mmc_host {
 	unsigned long		caps;		/* Host capabilities */
 
 #define MMC_CAP_4_BIT_DATA	(1 << 0)	/* Can the host do 4 bit transfers */
-#define MMC_CAP_MULTIWRITE	(1 << 1)	/* Can accurately report bytes sent to card on error */
-#define MMC_CAP_MMC_HIGHSPEED	(1 << 2)	/* Can do MMC high-speed timing */
-#define MMC_CAP_SD_HIGHSPEED	(1 << 3)	/* Can do SD high-speed timing */
-#define MMC_CAP_SDIO_IRQ	(1 << 4)	/* Can signal pending SDIO IRQs */
-#define MMC_CAP_SPI		(1 << 5)	/* Talks only SPI protocols */
-#define MMC_CAP_NEEDS_POLL	(1 << 6)	/* Needs polling for card-detection */
+#define MMC_CAP_MMC_HIGHSPEED	(1 << 1)	/* Can do MMC high-speed timing */
+#define MMC_CAP_SD_HIGHSPEED	(1 << 2)	/* Can do SD high-speed timing */
+#define MMC_CAP_SDIO_IRQ	(1 << 3)	/* Can signal pending SDIO IRQs */
+#define MMC_CAP_SPI		(1 << 4)	/* Talks only SPI protocols */
+#define MMC_CAP_NEEDS_POLL	(1 << 5)	/* Needs polling for card-detection */
 
 	/* host specific block data */
 	unsigned int		max_seg_size;	/* see blk_queue_max_segment_size */