mmc: dw_mmc: Fix PIO mode with support of highmem

Current PIO mode makes a kernel crash with CONFIG_HIGHMEM.
Highmem pages have a NULL from sg_virt(sg).
This patch fixes the following problem.

Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 817 [#1] PREEMPT SMP
Modules linked in:
CPU: 0    Not tainted  (3.0.15-01423-gdbf465f #589)
PC is at dw_mci_pull_data32+0x4c/0x9c
LR is at dw_mci_read_data_pio+0x54/0x1f0
pc : [<c0358824>]    lr : [<c035988c>]    psr: 20000193
sp : c0619d48  ip : c0619d70  fp : c0619d6c
r10: 00000000  r9 : 00000002  r8 : 00001000
r7 : 00000200  r6 : 00000000  r5 : e1dd3100  r4 : 00000000
r3 : 65622023  r2 : 0000007f  r1 : eeb96000  r0 : e1dd3100
Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment
xkernel
Control: 10c5387d  Table: 61e2004a  DAC: 00000015
Process swapper (pid: 0, stack limit = 0xc06182f0)
Stack: (0xc0619d48 to 0xc061a000)
9d40:                   e1dd3100 e1a4f000 00000000 e1dd3100 e1a4f000 00000200
9d60: c0619da4 c0619d70 c035988c c03587e4 c0619d9c e18158f4 e1dd3100 e1dd3100
9d80: 00000020 00000000 00000000 00000020 c06e8a84 00000000 c0619e04 c0619da8
9da0: c0359b24 c0359844 e18158f4 e1dd3164 e1dd3168 e1dd3150 3d02fc79 e1dd3154
9dc0: e1dd3178 00000000 00000020 00000000 e1dd3150 00000000 c10dd7e8 e1a84900
9de0: c061e7cc 00000000 00000000 0000008d c06e8a84 c061e780 c0619e4c c0619e08
9e00: c00c4738 c0359a34 3d02fc79 00000000 c0619e4c c05a1698 c05a1670 c05a165c
9e20: c04de8b0 c061e780 c061e7cc e1a84900 ffffed68 0000008d c0618000 00000000
9e40: c0619e6c c0619e50 c00c48b4 c00c46c8 c061e780 c00423ac c061e7cc ffffed68
9e60: c0619e8c c0619e70 c00c7358 c00c487c 0000008d ffffee38 c0618000 ffffed68
9e80: c0619ea4 c0619e90 c00c4258 c00c72b0 c00423ac ffffee38 c0619ecc c0619ea8
9ea0: c004241c c00c4234 ffffffff f8810000 0000006d 00000002 00000001 7fffffff
9ec0: c0619f44 c0619ed0 c0048bc0 c00423c4 220ae7a9 00000000 386f0d30 0005d3a4
9ee0: c00423ac c10dd0b8 c06f2cd8 c0618000 c0594778 c003a674 7fffffff c0619f44
9f00: 386f0d30 c0619f18 c00a6f94 c005be3c 80000013 ffffffff 386f0d30 0005d3a4
9f20: 386f0d30 0005d2d1 c10dd0a8 c10dd0b8 c06f2cd8 c0618000 c0619f74 c0619f48
9f40: c0345858 c005be00 c00a2440 c0618000 c0618000 c00410d8 c06c1944 c00410fc
9f60: c0594778 c003a674 c0619f9c c0619f78 c004a7e8 c03457b4 c0618000 c06c18f8
9f80: 00000000 c0039c70 c06c18d4 c003a674 c0619fb4 c0619fa0 c04ceafc c004a714
9fa0: c06287b4 c06c18f8 c0619ff4 c0619fb8 c0008b68 c04cea68 c0008578 00000000
9fc0: 00000000 c003a674 00000000 10c5387d c0628658 c003aa78 c062f1c4 4000406a
9fe0: 413fc090 00000000 00000000 c0619ff8 40008044 c0008858 00000000 00000000
Backtrace:
[<c03587d8>] (dw_mci_pull_data32+0x0/0x9c) from [<c035988c>] (dw_mci_read_data_pio+0x54/0x1f0)
 r6:00000200 r5:e1a4f000 r4:e1dd3100
 [<c0359838>] (dw_mci_read_data_pio+0x0/0x1f0) from [<c0359b24>] (dw_mci_interrupt+0xfc/0x4a4)
[<c0359a28>] (dw_mci_interrupt+0x0/0x4a4) from [<c00c4738>] (handle_irq_event_percpu+0x7c/0x1b4)
[<c00c46bc>] (handle_irq_event_percpu+0x0/0x1b4) from [<c00c48b4>] (handle_irq_event+0x44/0x64)
[<c00c4870>] (handle_irq_event+0x0/0x64) from [<c00c7358>] (handle_fasteoi_irq+0xb4/0x124)
 r7:ffffed68 r6:c061e7cc r5:c00423ac r4:c061e780
 [<c00c72a4>] (handle_fasteoi_irq+0x0/0x124) from [<c00c4258>] (generic_handle_irq+0x30/0x38)
 r7:ffffed68 r6:c0618000 r5:ffffee38 r4:0000008d
 [<c00c4228>] (generic_handle_irq+0x0/0x38) from [<c004241c>] (asm_do_IRQ+0x64/0xe0)
 r5:ffffee38 r4:c00423ac
 [<c00423b8>] (asm_do_IRQ+0x0/0xe0) from [<c0048bc0>] (__irq_svc+0x80/0x14c)
Exception stack(0xc0619ed0 to 0xc0619f18)
Signed-off-by: NSeungwon Jeon <tgih.jun@samsung.com>
Acked-by: NWill Newton <will.newton@imgtec.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/host/dw_mmc.c

@@ -22,7 +22,6 @@
 #include <linux/ioport.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
-#include <linux/scatterlist.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/stat.h>
@@ -502,8 +501,14 @@ static void dw_mci_submit_data(struct dw_mci *host, struct mmc_data *data)
 		host->dir_status = DW_MCI_SEND_STATUS;
 
 	if (dw_mci_submit_data_dma(host, data)) {
+		int flags = SG_MITER_ATOMIC;
+		if (host->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);
 		host->sg = data->sg;
-		host->pio_offset = 0;
 		host->part_buf_start = 0;
 		host->part_buf_count = 0;
 
@@ -972,6 +977,7 @@ static void dw_mci_tasklet_func(unsigned long priv)
 				 * generates a block interrupt, hence setting
 				 * the scatter-gather pointer to NULL.
 				 */
+				sg_miter_stop(&host->sg_miter);
 				host->sg = NULL;
 				ctrl = mci_readl(host, CTRL);
 				ctrl |= SDMMC_CTRL_FIFO_RESET;
@@ -1311,54 +1317,44 @@ static void dw_mci_pull_data(struct dw_mci *host, void *buf, int cnt)
 
 static void dw_mci_read_data_pio(struct dw_mci *host)
 {
-	struct scatterlist *sg = host->sg;
-	void *buf = sg_virt(sg);
-	unsigned int offset = host->pio_offset;
+	struct sg_mapping_iter *sg_miter = &host->sg_miter;
+	void *buf;
+	unsigned int offset;
 	struct mmc_data	*data = host->data;
 	int shift = host->data_shift;
 	u32 status;
 	unsigned int nbytes = 0, len;
+	unsigned int remain, fcnt;
 
 	do {
-		len = host->part_buf_count +
-			(SDMMC_GET_FCNT(mci_readl(host, STATUS)) << shift);
-		if (offset + len <= sg->length) {
+		if (!sg_miter_next(sg_miter))
+			goto done;
+
+		host->sg = sg_miter->__sg;
+		buf = sg_miter->addr;
+		remain = sg_miter->length;
+		offset = 0;
+
+		do {
+			fcnt = (SDMMC_GET_FCNT(mci_readl(host, STATUS))
+					<< shift) + host->part_buf_count;
+			len = min(remain, fcnt);
+			if (!len)
+				break;
 			dw_mci_pull_data(host, (void *)(buf + offset), len);
-
 			offset += len;
 			nbytes += len;
-
-			if (offset == sg->length) {
-				flush_dcache_page(sg_page(sg));
-				host->sg = sg = sg_next(sg);
-				if (!sg)
-					goto done;
-
-				offset = 0;
-				buf = sg_virt(sg);
-			}
-		} else {
-			unsigned int remaining = sg->length - offset;
-			dw_mci_pull_data(host, (void *)(buf + offset),
-					 remaining);
-			nbytes += remaining;
-
-			flush_dcache_page(sg_page(sg));
-			host->sg = sg = sg_next(sg);
-			if (!sg)
-				goto done;
-
-			offset = len - remaining;
-			buf = sg_virt(sg);
-			dw_mci_pull_data(host, buf, offset);
-			nbytes += offset;
-		}
+			remain -= len;
+		} while (remain);
+		sg_miter->consumed = offset;
 
 		status = mci_readl(host, MINTSTS);
 		mci_writel(host, RINTSTS, SDMMC_INT_RXDR);
 		if (status & DW_MCI_DATA_ERROR_FLAGS) {
 			host->data_status = status;
 			data->bytes_xfered += nbytes;
+			sg_miter_stop(sg_miter);
+			host->sg = NULL;
 			smp_wmb();
 
 			set_bit(EVENT_DATA_ERROR, &host->pending_events);
@@ -1367,65 +1363,66 @@ static void dw_mci_read_data_pio(struct dw_mci *host)
 			return;
 		}
 	} while (status & SDMMC_INT_RXDR); /*if the RXDR is ready read again*/
-	host->pio_offset = offset;
 	data->bytes_xfered += nbytes;
+
+	if (!remain) {
+		if (!sg_miter_next(sg_miter))
+			goto done;
+		sg_miter->consumed = 0;
+	}
+	sg_miter_stop(sg_miter);
 	return;
 
 done:
 	data->bytes_xfered += nbytes;
+	sg_miter_stop(sg_miter);
+	host->sg = NULL;
 	smp_wmb();
 	set_bit(EVENT_XFER_COMPLETE, &host->pending_events);
 }
 
 static void dw_mci_write_data_pio(struct dw_mci *host)
 {
-	struct scatterlist *sg = host->sg;
-	void *buf = sg_virt(sg);
-	unsigned int offset = host->pio_offset;
+	struct sg_mapping_iter *sg_miter = &host->sg_miter;
+	void *buf;
+	unsigned int offset;
 	struct mmc_data	*data = host->data;
 	int shift = host->data_shift;
 	u32 status;
 	unsigned int nbytes = 0, len;
+	unsigned int fifo_depth = host->fifo_depth;
+	unsigned int remain, fcnt;
 
 	do {
-		len = ((host->fifo_depth -
-			SDMMC_GET_FCNT(mci_readl(host, STATUS))) << shift)
-			- host->part_buf_count;
-		if (offset + len <= sg->length) {
+		if (!sg_miter_next(sg_miter))
+			goto done;
+
+		host->sg = sg_miter->__sg;
+		buf = sg_miter->addr;
+		remain = sg_miter->length;
+		offset = 0;
+
+		do {
+			fcnt = ((fifo_depth -
+				 SDMMC_GET_FCNT(mci_readl(host, STATUS)))
+					<< shift) - host->part_buf_count;
+			len = min(remain, fcnt);
+			if (!len)
+				break;
 			host->push_data(host, (void *)(buf + offset), len);
-
 			offset += len;
 			nbytes += len;
-			if (offset == sg->length) {
-				host->sg = sg = sg_next(sg);
-				if (!sg)
-					goto done;
-
-				offset = 0;
-				buf = sg_virt(sg);
-			}
-		} else {
-			unsigned int remaining = sg->length - offset;
-
-			host->push_data(host, (void *)(buf + offset),
-					remaining);
-			nbytes += remaining;
-
-			host->sg = sg = sg_next(sg);
-			if (!sg)
-				goto done;
-
-			offset = len - remaining;
-			buf = sg_virt(sg);
-			host->push_data(host, (void *)buf, offset);
-			nbytes += offset;
-		}
+			remain -= len;
+		} while (remain);
+		sg_miter->consumed = offset;
 
 		status = mci_readl(host, MINTSTS);
 		mci_writel(host, RINTSTS, SDMMC_INT_TXDR);
 		if (status & DW_MCI_DATA_ERROR_FLAGS) {
 			host->data_status = status;
 			data->bytes_xfered += nbytes;
+			sg_miter_stop(sg_miter);
+			host->sg = NULL;
 
 			smp_wmb();
 
@@ -1435,12 +1432,20 @@ static void dw_mci_write_data_pio(struct dw_mci *host)
 			return;
 		}
 	} while (status & SDMMC_INT_TXDR); /* if TXDR write again */
-	host->pio_offset = offset;
 	data->bytes_xfered += nbytes;
+
+	if (!remain) {
+		if (!sg_miter_next(sg_miter))
+			goto done;
+		sg_miter->consumed = 0;
+	}
+	sg_miter_stop(sg_miter);
 	return;
 
 done:
 	data->bytes_xfered += nbytes;
+	sg_miter_stop(sg_miter);
+	host->sg = NULL;
 	smp_wmb();
 	set_bit(EVENT_XFER_COMPLETE, &host->pending_events);
 }
@@ -1643,6 +1648,7 @@ static void dw_mci_work_routine_card(struct work_struct *work)
 				 * block interrupt, hence setting the
 				 * scatter-gather pointer to NULL.
 				 */
+				sg_miter_stop(&host->sg_miter);
 				host->sg = NULL;
 
 				ctrl = mci_readl(host, CTRL);

include/linux/mmc/dw_mmc.h

@@ -14,6 +14,8 @@
 #ifndef LINUX_MMC_DW_MMC_H
 #define LINUX_MMC_DW_MMC_H
 
+#include <linux/scatterlist.h>
+
 #define MAX_MCI_SLOTS	2
 
 enum dw_mci_state {
@@ -40,7 +42,7 @@ struct mmc_data;
  * @lock: Spinlock protecting the queue and associated data.
  * @regs: Pointer to MMIO registers.
  * @sg: Scatterlist entry currently being processed by PIO code, if any.
- * @pio_offset: Offset into the current scatterlist entry.
+ * @sg_miter: PIO mapping scatterlist iterator.
  * @cur_slot: The slot which is currently using the controller.
  * @mrq: The request currently being processed on @cur_slot,
  *	or NULL if the controller is idle.
@@ -115,7 +117,7 @@ struct dw_mci {
 	void __iomem		*regs;
 
 	struct scatterlist	*sg;
-	unsigned int		pio_offset;
+	struct sg_mapping_iter	sg_miter;
 
 	struct dw_mci_slot	*cur_slot;
 	struct mmc_request	*mrq;