On Mon, Nov 14, 2016 at 11:44:33AM +0200, Peter Ujfalusi wrote:
> On 11/14/2016 06:35 AM, Vinod Koul wrote:
> >> } else {
> >> - d->ccr |= CCR_DST_AMODE_CONSTANT | CCR_SRC_AMODE_POSTINC;
> >> d->csdp = CSDP_SRC_BURST_64 | CSDP_SRC_PACKED;
> >> +
> >> + d->ccr |= CCR_SRC_AMODE_POSTINC;
> >> + if (port_window) {
> >> + d->ccr |= CCR_DST_AMODE_DBLIDX;
> >> +
> >> + if (port_window / 64)
> >> + d->csdp = CSDP_DST_BURST_64 | CSDP_DST_PACKED;
> >> + else if (port_window / 32)
> >> + d->csdp = CSDP_DST_BURST_32 | CSDP_DST_PACKED;
> >> + else if (port_window / 16)
> >> + d->csdp = CSDP_DST_BURST_16 | CSDP_DST_PACKED;
> >
> > what does these mean?
>
> To optimize the speed on the write side. First check if the window size is
> multiple of 64 bytes, we enable the 64byte burst and packed transfer, if not
> try the 32bytes, then 16bytes.
> Same for the opposite direction previously.
Ah and how does client know the size of window..?
>
> >
> >> + } else {
> >> + d->ccr |= CCR_DST_AMODE_CONSTANT;
> >> + }
> >> }
> >>
> >> d->cicr = CICR_DROP_IE | CICR_BLOCK_IE;
> >> @@ -945,6 +979,9 @@ static struct dma_async_tx_descriptor
> >> *omap_dma_prep_slave_sg(
> >> d->ccr |= CCR_TRIGGER_SRC;
> >>
> >> d->cicr |= CICR_MISALIGNED_ERR_IE | CICR_TRANS_ERR_IE;
> >> +
> >> + if (port_window)
> >> + d->csdp |= CSDP_WRITE_LAST_NON_POSTED;
> >> }
> >> if (od->plat->errata & DMA_ERRATA_PARALLEL_CHANNELS)
> >> d->clnk_ctrl = c->dma_ch;
> >> @@ -970,6 +1007,10 @@ static struct dma_async_tx_descriptor
> >> *omap_dma_prep_slave_sg(
> >> osg->addr = sg_dma_address(sgent);
> >> osg->en = en;
> >> osg->fn = sg_dma_len(sgent) / frame_bytes;
> >> + if (port_window && dir == DMA_MEM_TO_DEV) {
> >> + osg->ei = 1;
> >> + osg->fi = (-1) * (port_window - 1);
> >> + }
> >
> > can you describe what you are trying here..
>
> The DMA is set up so one frame covers the port window. When the frame is
> finished we need to start reading the next frame from the start of the window
> again. The FI as (-1) * (port_window - 1) will take us to the start of the
> window. When the frame is finished the DMA is pointing to the last byte of the
> window.
Sound right to me, would help to add this as a comment..
--
~Vinod
