dmaengine: dw-edma: Fix invalid interleaved xfers semantics

The interleaved DMA transfer support added by 85e7518f42c8 ("dmaengine:
dw-edma: Add device_prep_interleave_dma() support") seems contradictory 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;

mean that numf can't be zero and frame_size must always be zero, otherwise
the transfer won't be executed. Furthermore, the transfer execution method
takes the frame 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, the multi-chunk
interleaved transfer turns to be unsupported even though the code implies
having it supported.

Add fully functioning support of 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 over all the chunks and frames by
initializing the number of the eDMA burst transactions 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.

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

Link: https://lore.kernel.org/r/20230113171409.30470-7-Sergey.Semin@baikalelectronics.ru
Fixes: 85e7518f42c8 ("dmaengine: dw-edma: Add device_prep_interleave_dma() support")
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Vinod Koul <vkoul@kernel.org>

1 files 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)