Re: [Qemu-devel] DMA active hw_error

[Richard Cole <richard.j.cole@gmail.com>]

I'll have to learn quite a bit more about QEMU and arm before I'll be
able to contribute back any patches. I bought a beagle board today so
that at least is a start, being able to compare QEMU to some real
hardware.

Out of curiosity what is the testing strategy for QEMU. Does one
simply write stand alone test programs that are then executed via qemu
or is there a more unit test kind of approach? I'm quite new to
emulators and such.

Is there an issues list for QEMU. Does anyone use github features like
being able to comment on particular sources lines or create issues
refer to specific lines of code? That would seem a good way to track
bugs discovered in the code.

A more broad question. Does anyone know why linux doesn't use the DMA?
Is the DMA really old school (I grew up with an Amiga that was full of
them), or is it just for portability, i.e that DMA differ from
platform to platform too much?

regards,

Richard.

On Tue, Dec 27, 2011 at 2:39 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 27 December 2011 03:21, Richard Cole <richard.j.cole@gmail.com> wrote:
>> Another thing I don't understand is the code from this function
>
>>  switch(offset >> 2)
>>    case 0:
>>      // src address register
>>
>> but 0x100 >> 2 does not equal 0. Not even close. Maybe it should be
>>
>>  (offset - 0x100) >> 2?
>>
>> But that would only work for channel 0. I guess one would then need to
>> mod by the size of the channel struct.
>
> (offset & 0x1f) >> 2
> is probably what you want. (you can see we just used 0xe0 to get
> the channel number).
>
>> Am I completely off base or has this code never been run?
>
> I expect it hasn't, no. You may be detecting a pattern here :-)
>
> Free extra bug if you're collecting them: the code that chases
> linked lists doesn't handle ch->lli bit 0 properly (it's the
> AHB master select bit, so it (and bit 1) should be ignored
> when using it as a pointer to load from).
>
> -- PMM