renegade-project/linux-next
2
0
Fork 0
mirror of https://github.com/edk2-porting/linux-next.git synced 2025-01-11 23:23:52 +08:00
Code

dmaengine: rcar-dmac: Work around descriptor mode IOMMU errata

Browse Source 
When descriptor memory is accessed through an IOMMU the DMADAR register
isn't initialized automatically from the first descriptor at beginning
of transfer by the DMAC like it should. Initialize it manually with the
destination address of the first chunk.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Laurent Pinchart 2015-01-27 18:33:29 +02:00 committed by Vinod Koul
parent 6a634808e3
commit 3f46306127
1 changed files with 14 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/dma/sh/rcar-dmac.c
View File

@ -325,6 +325,8 @@ static void rcar_dmac_chan_start_xfer(struct rcar_dmac_chan *chan)
rcar_dmac_chan_write(chan, RCAR_DMARS, chan->mid_rid);
if (desc->hwdescs.use) {
struct rcar_dmac_xfer_chunk *chunk;
dev_dbg(chan->chan.device->dev,
"chan%u: queue desc %p: %u@%pad\n",
chan->index, desc, desc->nchunks, &desc->hwdescs.dma);
@ -340,6 +342,18 @@ static void rcar_dmac_chan_start_xfer(struct rcar_dmac_chan *chan)
RCAR_DMACHCRB_DCNT(desc->nchunks - 1) |
RCAR_DMACHCRB_DRST);
/*
* Errata: When descriptor memory is accessed through an IOMMU
* the DMADAR register isn't initialized automatically from the
* first descriptor at beginning of transfer by the DMAC like it
* should. Initialize it manually with the destination address
* of the first chunk.
*/
chunk = list_first_entry(&desc->chunks,
struct rcar_dmac_xfer_chunk, node);
rcar_dmac_chan_write(chan, RCAR_DMADAR,
chunk->dst_addr & 0xffffffff);
/*
* Program the descriptor stage interrupt to occur after the end
* of the first stage.