[PATCH 1/3] dt/bindings: arm-pl330: add description of arm,pl330-periph-burst

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:

quoted

Hi Lars-Peter,

? 2016/8/9 16:39, Lars-Peter Clausen ??:

quoted

On 08/05/2016 09:25 AM, Shawn Lin wrote:

quoted

Hi Vinod,

? 2016/8/5 11:34, Vinod Koul ??:

quoted

On Fri, Aug 05, 2016 at 10:53:20AM +0800, Shawn Lin wrote:

quoted

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