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| author | Daniel Silsby <dansilsby@gmail.com> | 2018-08-29 23:32:55 +0200 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2018-09-11 12:59:26 +0530 |
| commit | 9e4e3a4c00c0af333d1c32925b80d12dc571778b (patch) | |
| tree | 0d09af38eddbd6b52b5ada44dacb36dc6daf4342 | |
| parent | f3c045dffe738fb2de534a8156f540dff42c315e (diff) | |
| download | linux-9e4e3a4c00c0af333d1c32925b80d12dc571778b.tar.bz2 | |
dmaengine: dma-jz4780: Set DTCn register explicitly
Normally, we wouldn't set the channel transfer count register directly
when using descriptor-driven transfers. However, there is no harm in
doing so, and it allows jz4780_dma_desc_residue() to report the correct
residue of an ongoing transfer, no matter when it is called.
Signed-off-by: Daniel Silsby <dansilsby@gmail.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
| -rw-r--r-- | drivers/dma/dma-jz4780.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c index d055602a92ca..d3b915ec8a09 100644 --- a/drivers/dma/dma-jz4780.c +++ b/drivers/dma/dma-jz4780.c @@ -532,6 +532,15 @@ static void jz4780_dma_begin(struct jz4780_dma_chan *jzchan) jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DRT, jzchan->transfer_type); + /* + * Set the transfer count. This is redundant for a descriptor-driven + * transfer. However, there can be a delay between the transfer start + * time and when DTCn reg contains the new transfer count. Setting + * it explicitly ensures residue is computed correctly at all times. + */ + jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DTC, + jzchan->desc->desc[jzchan->curr_hwdesc].dtc); + /* Write descriptor address and initiate descriptor fetch. */ desc_phys = jzchan->desc->desc_phys + (jzchan->curr_hwdesc * sizeof(*jzchan->desc->desc)); |