| Message ID | 20180721110643.19624-14-paul@crapouillou.net (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
On 07/21/2018 04:06 AM, Paul Cercueil wrote: > From: Daniel Silsby <dansilsby@gmail.com> > > 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> > Tested-by: Mathieu Malaterre <malat@debian.org> > --- > drivers/dma/dma-jz4780.c | 9 +++++++++ > 1 file changed, 9 insertions(+) Hi, Documentation/process/submitting-patches.rst says: The Signed-off-by: tag indicates that the signer was involved in the development of the patch, or that he/she was in the patch's delivery path. That means that patches that are from Daniel but you send (delivery path) should also be Signed-off-by: you.
diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c index cc2a86844db4..78849131c81d 100644 --- a/drivers/dma/dma-jz4780.c +++ b/drivers/dma/dma-jz4780.c @@ -530,6 +530,15 @@ 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));