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dmaengine: dma-jz4780: Set DTCn register explicitly

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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 <[email protected]>
Signed-off-by: Paul Cercueil <[email protected]>
Tested-by: Mathieu Malaterre <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>
This commit is contained in:
Daniel Silsby 2018-08-29 23:32:55 +02:00 • committed by Vinod Koul
commit 9e4e3a4c00
1 changed files with 9 additions and 0 deletions
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9
drivers/dma/dma-jz4780.c
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@ -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));