[PATCH V4 1/3] i2c: qup: Fix broken dma when CONFIG_DEBUG_SG is enabled

[Sricharan R <sricharan@codeaurora.org>]

With CONFIG_DEBUG_SG is enabled and when dma mode is used, below dump is seen,

------------[ cut here ]------------
kernel BUG at include/linux/scatterlist.h:140!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.0-00459-g9f087b9-dirty #7
Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
task: ffffffc036868000 ti: ffffffc036870000 task.ti: ffffffc036870000
PC is at qup_sg_set_buf.isra.13+0x138/0x154
LR is at qup_sg_set_buf.isra.13+0x50/0x154
pc : [<ffffffc0005a0ed8>] lr : [<ffffffc0005a0df0>] pstate: 60000145
sp : ffffffc0368735c0
x29: ffffffc0368735c0 x28: ffffffc036873752
x27: ffffffc035233018 x26: ffffffc000c4e000
x25: 0000000000000000 x24: 0000000000000004
x23: 0000000000000000 x22: ffffffc035233668
x21: ffffff80004e3000 x20: ffffffc0352e0018
x19: 0000004000000000 x18: 0000000000000028
x17: 0000000000000004 x16: ffffffc0017a39c8
x15: 0000000000001cdf x14: ffffffc0019929d8
x13: ffffffc0352e0018 x12: 0000000000000000
x11: 0000000000000001 x10: 0000000000000001
x9 : ffffffc0012b2d70 x8 : ffffff80004e3000
x7 : 0000000000000018 x6 : 0000000030000000
x5 : ffffffc00199f018 x4 : ffffffc035233018
x3 : 0000000000000004 x2 : 00000000c0000000
x1 : 0000000000000003 x0 : 0000000000000000

Process swapper/0 (pid: 1, stack limit = 0xffffffc036870020)
Stack: (0xffffffc0368735c0 to 0xffffffc036874000)

sg_set_bug expects that the buf parameter passed in should be from
lowmem and a valid pageframe. This is not true for pages from
dma_alloc_coherent which can be carveouts, hence the check fails.
Change allocation of sg buffers from dma_coherent memory to kzalloc
to fix the issue. Note that now dma_map/unmap is used to make the
kzalloc'ed buffers coherent before passing it to the dmaengine.

Signed-off-by: Sricharan R <sricharan@codeaurora.org>
Reviewed-by: Andy Gross <andy.gross@linaro.org>
---
 drivers/i2c/busses/i2c-qup.c | 51 +++++++++++++-------------------------------
 1 file changed, 15 insertions(+), 36 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index cc6439ab..43adc2d 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -585,8 +585,8 @@ static void qup_i2c_bam_cb(void *data)
 }
 
 static int qup_sg_set_buf(struct scatterlist *sg, void *buf,
-			  struct qup_i2c_tag *tg, unsigned int buflen,
-			  struct qup_i2c_dev *qup, int map, int dir)
+			  unsigned int buflen, struct qup_i2c_dev *qup,
+			  int dir)
 {
 	int ret;
 
@@ -595,9 +595,6 @@ static int qup_sg_set_buf(struct scatterlist *sg, void *buf,
 	if (!ret)
 		return -EINVAL;
 
-	if (!map)
-		sg_dma_address(sg) = tg->addr + ((u8 *)buf - tg->start);
-
 	return 0;
 }
 
@@ -670,16 +667,15 @@ static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
 				/* scratch buf to read the start and len tags */
 				ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
 						     &qup->brx.tag.start[0],
-						     &qup->brx.tag,
-						     2, qup, 0, 0);
+						     2, qup, DMA_FROM_DEVICE);
 
 				if (ret)
 					return ret;
 
 				ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
 						     &msg->buf[limit * i],
-						     NULL, tlen, qup,
-						     1, DMA_FROM_DEVICE);
+						     tlen, qup,
+						     DMA_FROM_DEVICE);
 				if (ret)
 					return ret;
 
@@ -688,7 +684,7 @@ static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
 			}
 			ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
 					     &qup->start_tag.start[off],
-					     &qup->start_tag, len, qup, 0, 0);
+					     len, qup, DMA_TO_DEVICE);
 			if (ret)
 				return ret;
 
@@ -696,8 +692,7 @@ static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
 			/* scratch buf to read the BAM EOT and FLUSH tags */
 			ret = qup_sg_set_buf(&qup->brx.sg[rx_buf++],
 					     &qup->brx.tag.start[0],
-					     &qup->brx.tag, 2,
-					     qup, 0, 0);
+					     2, qup, DMA_FROM_DEVICE);
 			if (ret)
 				return ret;
 		} else {
@@ -709,17 +704,15 @@ static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
 				len = qup_i2c_set_tags(tags, qup, msg, 1);
 
 				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
-						     tags,
-						     &qup->start_tag, len,
-						     qup, 0, 0);
+						     tags, len,
+						     qup, DMA_TO_DEVICE);
 				if (ret)
 					return ret;
 
 				tx_len += len;
 				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
 						     &msg->buf[limit * i],
-						     NULL, tlen, qup, 1,
-						     DMA_TO_DEVICE);
+						     tlen, qup, DMA_TO_DEVICE);
 				if (ret)
 					return ret;
 				i++;
@@ -738,8 +731,7 @@ static int qup_i2c_bam_do_xfer(struct qup_i2c_dev *qup, struct i2c_msg *msg,
 							QUP_BAM_FLUSH_STOP;
 				ret = qup_sg_set_buf(&qup->btx.sg[tx_buf++],
 						     &qup->btx.tag.start[0],
-						     &qup->btx.tag, len,
-						     qup, 0, 0);
+						     len, qup, DMA_TO_DEVICE);
 				if (ret)
 					return ret;
 				tx_nents += 1;
@@ -1407,27 +1399,21 @@ static int qup_i2c_probe(struct platform_device *pdev)
 
 		/* 2 tag bytes for each block + 5 for start, stop tags */
 		size = blocks * 2 + 5;
-		qup->dpool = dma_pool_create("qup_i2c-dma-pool", &pdev->dev,
-					     size, 4, 0);
 
-		qup->start_tag.start = dma_pool_alloc(qup->dpool, GFP_KERNEL,
-						      &qup->start_tag.addr);
+		qup->start_tag.start = devm_kzalloc(&pdev->dev,
+						    size, GFP_KERNEL);
 		if (!qup->start_tag.start) {
 			ret = -ENOMEM;
 			goto fail_dma;
 		}
 
-		qup->brx.tag.start = dma_pool_alloc(qup->dpool,
-						    GFP_KERNEL,
-						    &qup->brx.tag.addr);
+		qup->brx.tag.start = devm_kzalloc(&pdev->dev, 2, GFP_KERNEL);
 		if (!qup->brx.tag.start) {
 			ret = -ENOMEM;
 			goto fail_dma;
 		}
 
-		qup->btx.tag.start = dma_pool_alloc(qup->dpool,
-						    GFP_KERNEL,
-						    &qup->btx.tag.addr);
+		qup->btx.tag.start = devm_kzalloc(&pdev->dev, 2, GFP_KERNEL);
 		if (!qup->btx.tag.start) {
 			ret = -ENOMEM;
 			goto fail_dma;
@@ -1566,13 +1552,6 @@ static int qup_i2c_remove(struct platform_device *pdev)
 	struct qup_i2c_dev *qup = platform_get_drvdata(pdev);
 
 	if (qup->is_dma) {
-		dma_pool_free(qup->dpool, qup->start_tag.start,
-			      qup->start_tag.addr);
-		dma_pool_free(qup->dpool, qup->brx.tag.start,
-			      qup->brx.tag.addr);
-		dma_pool_free(qup->dpool, qup->btx.tag.start,
-			      qup->btx.tag.addr);
-		dma_pool_destroy(qup->dpool);
 		dma_release_channel(qup->btx.dma);
 		dma_release_channel(qup->brx.dma);
 	}
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation