On Wed, Aug 17, 2016 at 04:11:03PM +0800, Shawn Lin wrote: > Hi, Vinod and Lars-Peter > > Ping.. Any better idea to share :) > > On 2016/8/9 17:12, Shawn Lin wrote: > >Hi Lars-Peter, > > > >在 2016/8/9 16:39, Lars-Peter Clausen 写道: > >>On 08/05/2016 09:25 AM, Shawn Lin wrote: > >>>Hi Vinod, > >>> > >>>在 2016/8/5 11:34, Vinod Koul 写道: > >>>>On Fri, Aug 05, 2016 at 10:53:20AM +0800, Shawn Lin wrote: > >>>>>This patch adds the "arm,pl330-periph-burst" for arm-pl330 to > >>>>>support busrt mode. > >>>> > >>>>why should this be DT property. Only reason I can think of if some hw > >>>>versions support this and some won't. > >>> > >>>yes, if we want to support burst mode, both of the master(pl330) and > >>>client(several peripherals) should implement it, otherwise it will > >>>be broken when enabling. > >> > >>As you said, it is up to the consumer peripheral whether it supports > >>BURST, > >>SINGLE or both. So this is a per client property, but you specify this > >>as a > >>a global property on the producer side. > > > >Thanks for comment. > > > >yup, but what is the proper way to add it ? :) > > > > > >a) If pl330 support BURST as well as all the peripherals, we could > >enable it. > > > >b) If pl300 support BURST, but all the peripherals don't support it, > >we could not enable it. > > > >c) If pl300 support BURST, but not all the peripherals support it, > >we also could not enable it. > > > >the burst feature of peripheral IP may be vendor-specific, but the > >common driver for this peripheral are used for many many vendors which > >means we could not check all of this info. It's very likely to break > >them... I couldn't figure out how many upstreamed peripheral drivers > >who are using pl300 either. > > > >So this check should be done by all this vendors but we could make > >sure we don't break them before they check a), b), c), right? Since support for BURST needs to be from peripheral too, we should have that as a property for peripheral not for controller. The peripheral drivers can communicate the burst to be used to pl330 using src_maxburst/dst_maxburst in dma_slave_config. We can use this value to indicate the DMA should be single (a value of 0) or burst with "burst" value. -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
