Commit 7ad06f21 authored Jan 13, 2023 by Serge Semin Committed by Lorenzo Pieralisi Jan 27, 2023

dmaengine: dw-edma: Fix invalid interleaved xfers semantics

The interleaved DMA transfer support added by 85e7518f ("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: 85e7518f ("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>

parent c8ed4918

drivers/dma/dw-edma/dw-edma-core.c

+7 −11

Original line number	Diff line number	Diff line
		@@ -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)