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

From: Sricharan
Date: Fri Jun 10 2016 - 14:14:59 EST

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+Wolfram Sang

>-----Original Message-----
>From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Sricharan R
>Sent: Friday, June 10, 2016 11:38 PM
>To: linux-arm-msm@xxxxxxxxxxxxxxx; ntelkar@xxxxxxxxxxxxxx; galak@xxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>andy.gross@xxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; agross@xxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
>nkaje@xxxxxxxxxxxxxx; absahu@xxxxxxxxxxxxxx
>Cc: sricharan@xxxxxxxxxxxxxx
>Subject: [PATCH V4 1/3] i2c: qup: Fix broken dma when CONFIG_DEBUG_SG is enabled
>
>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@xxxxxxxxxxxxxx>
>Reviewed-by: Andy Gross <andy.gross@xxxxxxxxxx>
>---
> 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
>
>
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>linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
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In reply to: Sricharan R: "[PATCH V4 1/3] i2c: qup: Fix broken dma when CONFIG_DEBUG_SG is enabled"
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