[Letux-kernel] DMA driver (was Re: [PATCH 00/20] A bunch of JZ4730 fixups for letux-kernel)

H. Nikolaus Schaller hns at goldelico.com
Fri Jan 15 09:49:34 CET 2021

Hi Paul,

> Am 15.01.2021 um 00:49 schrieb Paul Boddie <paul at boddie.org.uk>:
> On Tuesday, 12 January 2021 15:17:13 CET H. Nikolaus Schaller wrote:
>> Am 11.01.2021 um 22:59 schrieb Paul Boddie <paul at boddie.org.uk>:
>>> (I have been investigating the DMA controller and have demonstrated it
>>> working under L4Re, so I will now try and apply the lessons to the Linux
>>> driver.)
>> That will be great!
> I found one problem with my earlier changes: the IRQ pending register on the 
> JZ4730 has the flags in a different place and in reverse order. The additional 
> patch supplied here updates the previous changes to hopefully fix interrupt 
> flag testing.
> Paul<0001-JZ4730-Fixed-DMA-interrupt-pending-tests.patch>

Thanks! I gave it a try but we still have the waiting for mmc issue.

Hm. Maybe we need a different test strategy.

Boot with non-dma MMC driver and try to use DMA for something else after
successful boot. Maybe a dummy driver which just tries to copy bytes around
which can be loaded through modprobe from the command line?

Then we can easily inspect register values and activities of the isolated
driver and how it interacts with the DMA controller registers.


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