ARM: 6237/1: mmci: use sg_miter API to fix multi-page sg handling

The mmci driver's SG list iteration logic assumes that each SG entry
spans only one page, and only maps and flushes one page of the sg.  This
is not a valid assumption.  Fix it by converting the driver to the
sg_miter API, which correctly handles sgs which span multiple pages.

Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/mmc/host/mmci.c

@@ -26,7 +26,6 @@
 #include <linux/amba/mmci.h>
 #include <linux/regulator/consumer.h>
 
-#include <asm/cacheflush.h>
 #include <asm/div64.h>
 #include <asm/io.h>
 #include <asm/sizes.h>
@@ -98,6 +97,18 @@ static void mmci_stop_data(struct mmci_host *host)
 	host->data = NULL;
 }
 
+static void mmci_init_sg(struct mmci_host *host, struct mmc_data *data)
+{
+	unsigned int flags = SG_MITER_ATOMIC;
+
+	if (data->flags & MMC_DATA_READ)
+		flags |= SG_MITER_TO_SG;
+	else
+		flags |= SG_MITER_FROM_SG;
+
+	sg_miter_start(&host->sg_miter, data->sg, data->sg_len, flags);
+}
+
 static void mmci_start_data(struct mmci_host *host, struct mmc_data *data)
 {
 	unsigned int datactrl, timeout, irqmask;
@@ -210,8 +221,17 @@ mmci_data_irq(struct mmci_host *host, struct mmc_data *data,
 		 * We hit an error condition.  Ensure that any data
 		 * partially written to a page is properly coherent.
 		 */
-		if (host->sg_len && data->flags & MMC_DATA_READ)
-			flush_dcache_page(sg_page(host->sg_ptr));
+		if (data->flags & MMC_DATA_READ) {
+			struct sg_mapping_iter *sg_miter = &host->sg_miter;
+			unsigned long flags;
+
+			local_irq_save(flags);
+			if (sg_miter_next(sg_miter)) {
+				flush_dcache_page(sg_miter->page);
+				sg_miter_stop(sg_miter);
+			}
+			local_irq_restore(flags);
+		}
 	}
 	if (status & MCI_DATAEND) {
 		mmci_stop_data(host);
@@ -314,15 +334,18 @@ static int mmci_pio_write(struct mmci_host *host, char *buffer, unsigned int rem
 static irqreturn_t mmci_pio_irq(int irq, void *dev_id)
 {
 	struct mmci_host *host = dev_id;
+	struct sg_mapping_iter *sg_miter = &host->sg_miter;
 	void __iomem *base = host->base;
+	unsigned long flags;
 	u32 status;
 
 	status = readl(base + MMCISTATUS);
 
 	dev_dbg(mmc_dev(host->mmc), "irq1 (pio) %08x\n", status);
 
+	local_irq_save(flags);
+
 	do {
-		unsigned long flags;
 		unsigned int remain, len;
 		char *buffer;
 
@@ -336,11 +359,11 @@ static irqreturn_t mmci_pio_irq(int irq, void *dev_id)
 		if (!(status & (MCI_TXFIFOHALFEMPTY|MCI_RXDATAAVLBL)))
 			break;
 
-		/*
-		 * Map the current scatter buffer.
-		 */
-		buffer = mmci_kmap_atomic(host, &flags) + host->sg_off;
-		remain = host->sg_ptr->length - host->sg_off;
+		if (!sg_miter_next(sg_miter))
+			break;
+
+		buffer = sg_miter->addr;
+		remain = sg_miter->length;
 
 		len = 0;
 		if (status & MCI_RXACTIVE)
@@ -348,31 +371,24 @@ static irqreturn_t mmci_pio_irq(int irq, void *dev_id)
 		if (status & MCI_TXACTIVE)
 			len = mmci_pio_write(host, buffer, remain, status);
 
-		/*
-		 * Unmap the buffer.
-		 */
-		mmci_kunmap_atomic(host, buffer, &flags);
+		sg_miter->consumed = len;
 
-		host->sg_off += len;
 		host->size -= len;
 		remain -= len;
 
 		if (remain)
 			break;
 
-		/*
-		 * If we were reading, and we have completed this
-		 * page, ensure that the data cache is coherent.
-		 */
 		if (status & MCI_RXACTIVE)
-			flush_dcache_page(sg_page(host->sg_ptr));
-
-		if (!mmci_next_sg(host))
-			break;
+			flush_dcache_page(sg_miter->page);
 
 		status = readl(base + MMCISTATUS);
 	} while (1);
 
+	sg_miter_stop(sg_miter);
+
+	local_irq_restore(flags);
+
 	/*
 	 * If we're nearing the end of the read, switch to
 	 * "any data available" mode.

drivers/mmc/host/mmci.h

@@ -171,42 +171,9 @@ struct mmci_host {
 	struct timer_list	timer;
 	unsigned int		oldstat;
 
-	unsigned int		sg_len;
-
 	/* pio stuff */
-	struct scatterlist	*sg_ptr;
-	unsigned int		sg_off;
+	struct sg_mapping_iter	sg_miter;
 	unsigned int		size;
 	struct regulator	*vcc;
 };
 
-static inline void mmci_init_sg(struct mmci_host *host, struct mmc_data *data)
-{
-	/*
-	 * Ideally, we want the higher levels to pass us a scatter list.
-	 */
-	host->sg_len = data->sg_len;
-	host->sg_ptr = data->sg;
-	host->sg_off = 0;
-}
-
-static inline int mmci_next_sg(struct mmci_host *host)
-{
-	host->sg_ptr++;
-	host->sg_off = 0;
-	return --host->sg_len;
-}
-
-static inline char *mmci_kmap_atomic(struct mmci_host *host, unsigned long *flags)
-{
-	struct scatterlist *sg = host->sg_ptr;
-
-	local_irq_save(*flags);
-	return kmap_atomic(sg_page(sg), KM_BIO_SRC_IRQ) + sg->offset;
-}
-
-static inline void mmci_kunmap_atomic(struct mmci_host *host, void *buffer, unsigned long *flags)
-{
-	kunmap_atomic(buffer, KM_BIO_SRC_IRQ);
-	local_irq_restore(*flags);
-}