From: Vinod Koul <vinod.koul@intel.com>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: dan.j.williams@intel.com, Tony Lindgren <tony@atomide.com>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-omap@vger.kernel.org, arnd@arndb.de
Subject: Re: [PATCH 2/2] dmaengine: omap-dma: Support for slave devices with data port window
Date: Mon, 14 Nov 2016 16:25:46 +0530 [thread overview]
Message-ID: <20161114105546.GF3000@localhost> (raw)
In-Reply-To: <11c9dee6-1ddf-f2d3-e616-73fbac7cfd4f@ti.com>
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
next prev parent reply other threads:[~2016-11-14 10:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-25 10:50 [PATCH 0/2] dmaengine: core/omap-dma: Support for port window Peter Ujfalusi
2016-10-25 10:50 ` [PATCH 1/2] dmaengine: dma_slave_config: add support for slave " Peter Ujfalusi
2016-10-25 10:50 ` [PATCH 2/2] dmaengine: omap-dma: Support for slave devices with data " Peter Ujfalusi
2016-11-14 4:35 ` Vinod Koul
2016-11-14 9:44 ` Peter Ujfalusi
2016-11-14 10:55 ` Vinod Koul [this message]
2016-11-14 11:49 ` Peter Ujfalusi
2016-11-14 10:53 ` Russell King - ARM Linux
2016-11-14 11:56 ` Peter Ujfalusi
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