Messages in this thread | | | Date | Mon, 13 Jun 2016 11:20:12 +0530 | From | Vinod Koul <> | Subject | Re: [PATCH v10 2/2] dmaengine: Add Xilinx zynqmp dma engine driver support |
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On Wed, Jun 08, 2016 at 07:40:52AM +0000, Appana Durga Kedareswara Rao wrote: > > > +static void zynqmp_dma_desc_config_eod(struct zynqmp_dma_chan *chan, > > > +void *desc) > > > > eod? 80 line?
What's eod?
> > > +int zynqmp_dma_channel_set_config(struct dma_chan *dchan, > > > + struct zynqmp_dma_config *cfg) > > > +{ > > > + struct zynqmp_dma_chan *chan = to_chan(dchan); > > > + > > > + chan->config.ovrfetch = cfg->ovrfetch; > > > + chan->config.has_sg = cfg->has_sg; > > > > is this HW capability? if so why would anyone not like to use it! > > Yes it is HW capability. It can be either in simple mode or SG mode > Earlier In the driver this configuration is read from the device-tree > But as per lars and your suggestion moved it as runtime config parameters.
If sg mode is available why would anyone _not_ want it?
I do not think there is point to have this
> > > > > > + chan->config.ratectrl = cfg->ratectrl; > > > + chan->config.src_issue = cfg->src_issue; > > > + chan->config.src_burst_len = cfg->src_burst_len; > > > + chan->config.dst_burst_len = cfg->dst_burst_len; > > > > can you describe these parameters? > ratectl: > Rate control can be independently enabled per channel. When rate control is enabled, the > DMA channel uses the rate control count to schedule successive data read transactions.
And how is this used by client?
> src_issue: > Tells outstanding transaction on SRC.
This should be read only then, right?
> Burst_len: > Configures the burst length of the src and dst transfers...
Hmmm, but you are on memcpy, so that should be programmed for throughput?
> > > > How would a client know how to configure them? > > With the default values of the config parameters driver will work.
But how will client know what is default!
> If user has specific requirement to change these parameters they can pass > It to the driver using set_config API and all these parameters are > Documented in the include/linux/dma/xilinx_dma.h file...
Can you give me an example where user would like to do that
-- ~Vinod
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