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Subject[PATCH v7 06/25] dmaengine: dw-edma: Fix invalid interleaved xfers semantics
Date
The interleaved DMA transfer support added in commit 85e7518f42c8
("dmaengine: dw-edma: Add device_prep_interleave_dma() support") seems
contradicting to what the DMA-engine defines. The next conditional
statements:
if (!xfer->xfer.il->numf)
return NULL;
if (xfer->xfer.il->numf > 0 && xfer->xfer.il->frame_size > 0)
return NULL;
basically mean that numf can't be zero and frame_size must always be zero,
otherwise the transfer won't be executed. But further the transfer
execution method takes the frames size from the
dma_interleaved_template.sgl[] array for each frame. That array in
accordance with [1] is supposed to be of
dma_interleaved_template.frame_size size, which as we discovered before
the code expects to be zero. So judging by the dw_edma_device_transfer()
implementation the method implies the dma_interleaved_template.sgl[] array
being of dma_interleaved_template.numf size, which is wrong. Since the
dw_edma_device_transfer() method doesn't permit
dma_interleaved_template.frame_size being non-zero then actual multi-chunk
interleaved transfer turns to be unsupported even though the code implies
having it supported.

Let's fix that by adding a fully functioning support of the interleaved
DMA transfers. First of all dma_interleaved_template.frame_size is
supposed to be greater or equal to one thus having at least simple linear
chunked frames. Secondly we can create a walk-through all over the chunks
and frames just by initializing the number of the eDMA burst transactios
as a multiple of dma_interleaved_template.numf and
dma_interleaved_template.frame_size and getting the frame_size-modulo of
the iteration step as an index of the dma_interleaved_template.sgl[]
array. The rest of the dw_edma_device_transfer() method code can be left
unchanged.

[1] include/linux/dmaengine.h: doc struct dma_interleaved_template

Fixes: 85e7518f42c8 ("dmaengine: dw-edma: Add device_prep_interleave_dma() support")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Vinod Koul <vkoul@kernel.org>
---
drivers/dma/dw-edma/dw-edma-core.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 35588e14f79a..d5c4192141ef 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -332,6 +332,7 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
struct dw_edma_chunk *chunk;
struct dw_edma_burst *burst;
struct dw_edma_desc *desc;
+ size_t fsz = 0;
u32 cnt = 0;
int i;

@@ -381,9 +382,7 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
if (xfer->xfer.sg.len < 1)
return NULL;
} else if (xfer->type == EDMA_XFER_INTERLEAVED) {
- if (!xfer->xfer.il->numf)
- return NULL;
- if (xfer->xfer.il->numf > 0 && xfer->xfer.il->frame_size > 0)
+ if (!xfer->xfer.il->numf || xfer->xfer.il->frame_size < 1)
return NULL;
if (!xfer->xfer.il->src_inc || !xfer->xfer.il->dst_inc)
return NULL;
@@ -413,10 +412,8 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
cnt = xfer->xfer.sg.len;
sg = xfer->xfer.sg.sgl;
} else if (xfer->type == EDMA_XFER_INTERLEAVED) {
- if (xfer->xfer.il->numf > 0)
- cnt = xfer->xfer.il->numf;
- else
- cnt = xfer->xfer.il->frame_size;
+ cnt = xfer->xfer.il->numf * xfer->xfer.il->frame_size;
+ fsz = xfer->xfer.il->frame_size;
}

for (i = 0; i < cnt; i++) {
@@ -438,7 +435,7 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
else if (xfer->type == EDMA_XFER_SCATTER_GATHER)
burst->sz = sg_dma_len(sg);
else if (xfer->type == EDMA_XFER_INTERLEAVED)
- burst->sz = xfer->xfer.il->sgl[i].size;
+ burst->sz = xfer->xfer.il->sgl[i % fsz].size;

chunk->ll_region.sz += burst->sz;
desc->alloc_sz += burst->sz;
@@ -481,10 +478,9 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)

if (xfer->type == EDMA_XFER_SCATTER_GATHER) {
sg = sg_next(sg);
- } else if (xfer->type == EDMA_XFER_INTERLEAVED &&
- xfer->xfer.il->frame_size > 0) {
+ } else if (xfer->type == EDMA_XFER_INTERLEAVED) {
struct dma_interleaved_template *il = xfer->xfer.il;
- struct data_chunk *dc = &il->sgl[i];
+ struct data_chunk *dc = &il->sgl[i % fsz];

src_addr += burst->sz;
if (il->src_sgl)
--
2.38.1

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