mmc: cull sg list to match mmc request size

mmc layer may introduce additional (compared to block layer) limits on
request size. Culling of the sg list to match adjusted request size
simplifies the handling of such cases in the low level driver, allowing
it to skip block count checks while processing sg entries.

(fixes for wbsd and sdhci by Pierre Ossman)

Signed-off-by: Alex Dubov <oakad@yahoo.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/mmc_block.c

@@ -223,7 +223,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 	struct mmc_blk_data *md = mq->data;
 	struct mmc_card *card = md->queue.card;
 	struct mmc_blk_request brq;
-	int ret = 1;
+	int ret = 1, sg_pos, data_size;
 
 	if (mmc_card_claim_host(card))
 		goto flush_queue;
@@ -283,6 +283,20 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 		brq.data.sg = mq->sg;
 		brq.data.sg_len = blk_rq_map_sg(req->q, req, brq.data.sg);
 
+		if (brq.data.blocks !=
+		    (req->nr_sectors >> (md->block_bits - 9))) {
+			data_size = brq.data.blocks * brq.data.blksz;
+			for (sg_pos = 0; sg_pos < brq.data.sg_len; sg_pos++) {
+				data_size -= mq->sg[sg_pos].length;
+				if (data_size <= 0) {
+					mq->sg[sg_pos].length += data_size;
+					sg_pos++;
+					break;
+				}
+			}
+			brq.data.sg_len = sg_pos;
+		}
+
 		mmc_wait_for_req(card->host, &brq.mrq);
 		if (brq.cmd.error) {
 			printk(KERN_ERR "%s: error %d sending read/write command\n",

drivers/mmc/sdhci.c

@@ -1,7 +1,7 @@
 /*
  *  linux/drivers/mmc/sdhci.c - Secure Digital Host Controller Interface driver
  *
- *  Copyright (C) 2005-2006 Pierre Ossman, All Rights Reserved.
+ *  Copyright (C) 2005-2007 Pierre Ossman, All Rights Reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -247,14 +247,13 @@ static void sdhci_read_block_pio(struct sdhci_host *host)
 			chunk_remain = min(blksize, 4);
 		}
 
-		size = min(host->size, host->remain);
-		size = min(size, chunk_remain);
+		size = min(host->remain, chunk_remain);
 
 		chunk_remain -= size;
 		blksize -= size;
 		host->offset += size;
 		host->remain -= size;
-		host->size -= size;
+
 		while (size) {
 			*buffer = data & 0xFF;
 			buffer++;
@@ -289,14 +288,13 @@ static void sdhci_write_block_pio(struct sdhci_host *host)
 	buffer = sdhci_sg_to_buffer(host) + host->offset;
 
 	while (blksize) {
-		size = min(host->size, host->remain);
-		size = min(size, chunk_remain);
+		size = min(host->remain, chunk_remain);
 
 		chunk_remain -= size;
 		blksize -= size;
 		host->offset += size;
 		host->remain -= size;
-		host->size -= size;
+
 		while (size) {
 			data >>= 8;
 			data |= (u32)*buffer << 24;
@@ -325,7 +323,7 @@ static void sdhci_transfer_pio(struct sdhci_host *host)
 
 	BUG_ON(!host->data);
 
-	if (host->size == 0)
+	if (host->num_sg == 0)
 		return;
 
 	if (host->data->flags & MMC_DATA_READ)
@@ -339,10 +337,8 @@ static void sdhci_transfer_pio(struct sdhci_host *host)
 		else
 			sdhci_write_block_pio(host);
 
-		if (host->size == 0)
+		if (host->num_sg == 0)
 			break;
-
-		BUG_ON(host->num_sg == 0);
 	}
 
 	DBG("PIO transfer complete.\n");
@@ -408,8 +404,6 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
 
 		writel(sg_dma_address(data->sg), host->ioaddr + SDHCI_DMA_ADDRESS);
 	} else {
-		host->size = data->blksz * data->blocks;
-
 		host->cur_sg = data->sg;
 		host->num_sg = data->sg_len;
 
@@ -473,10 +467,6 @@ static void sdhci_finish_data(struct sdhci_host *host)
 			"though there were blocks left.\n",
 			mmc_hostname(host->mmc));
 		data->error = MMC_ERR_FAILED;
-	} else if (host->size != 0) {
-		printk(KERN_ERR "%s: %d bytes were left untransferred.\n",
-			mmc_hostname(host->mmc), host->size);
-		data->error = MMC_ERR_FAILED;
 	}
 
 	DBG("Ending data transfer (%d bytes)\n", data->bytes_xfered);

drivers/mmc/sdhci.h

@@ -1,7 +1,7 @@
 /*
  *  linux/drivers/mmc/sdhci.h - Secure Digital Host Controller Interface driver
  *
- *  Copyright (C) 2005 Pierre Ossman, All Rights Reserved.
+ *  Copyright (C) 2005-2007 Pierre Ossman, All Rights Reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -187,8 +187,6 @@ struct sdhci_host {
 	int			offset;		/* Offset into current sg */
 	int			remain;		/* Bytes left in current */
 
-	int			size;		/* Remaining bytes in transfer */
-
 	char			slot_descr[20];	/* Name for reservations */
 
 	int			irq;		/* Device IRQ */