On 09/09/2013 04:53 PM, Mark Brown wrote:
On Mon, Sep 09, 2013 at 04:09:26PM +0200, Lukasz Czerwinski wrote:
This patch removes DMA channel initialization and deinitialization for each
transfer. Now DMA channel is requested only at the driver initialization
and stored in driver data.
So, this is fine but I had been under the impression that one of the
reasons that the channels were only being requested at transfer time was
that they could be used for other purposes too. If that is not the case
then fine, if that is the case then probably moving to prepare/unprepare
transfer hardware (when the clocks are enabled) would make more sense -
that'd avoid repeated allocations and frees while the controller is busy
which should be the main issue performance wise.
For 16kB buffer upload time is reduced from ~90ms to ~80ms (I tested
with S5C73M3 355560B transfer). If you think that performance increase
isn't valuable we should skip that patch.
amba-pl80 uses virtual DMA channels support so driver won't occupy all
the time physical channel. pl330 driver don't use such framework but It
will be very hard to occupy all channels at the same time. If I'm wrong
please correct me.
Thanks
Lukasz
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