Re: [Qemu-devel] DMA active hw_error

[Richard Cole]

Another thing I don't understand is the code from this function

  https://github.com/qemu/QEMU/blob/master/hw/pl080.c#L289

If I look here 
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0218e/ch03s04s15.html
it seems to suggest that the src register is located at:

  0x100 offset from the base of the device

but the function does this this:

  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.

Am I completely off base or has this code never been run?

regards,

Richard.

On Mon, Dec 26, 2011 at 6:26 PM, Richard Cole <address@hidden> wrote:
> I'm new to QEMU so this might be a rather naive question but why is
> there a hw_error here:
>
> https://github.com/qemu/QEMU/blob/2ac711791b2e4aabc5e4046b7428727828c705eb/hw/pl080.c#L96
>
> It causes QEMU at least on my machine to abort. It would seem to make
> it so the rest of the function will never be executed? That hw_error
> (or a cpu_error) line seems have have been there since the file was
> imported.
>
> Here's the code fragment in case that link doesn't work.
>
> static void pl080_run(pl080_state *s)
> {
>    int c;
>    int flow;
>    pl080_channel *ch;
>    int swidth;
>    int dwidth;
>    int xsize;
>    int n;
>    int src_id;
>    int dest_id;
>    int size;
>    uint8_t buff[4];
>    uint32_t req;
>
>    s->tc_mask = 0;
>    for (c = 0; c < s->nchannels; c++) {
>        if (s->chan[c].conf & PL080_CCONF_ITC)
>            s->tc_mask |= 1 << c;
>        if (s->chan[c].conf & PL080_CCONF_IE)
>            s->err_mask |= 1 << c;
>    }
>
>    if ((s->conf & PL080_CONF_E) == 0)
>        return;
>
> hw_error("DMA active\n");
>    /* If we are already in the middle of a DMA operation then indicate that
>       there may be new DMA requests and return immediately.  */
>    if (s->running) {
>        s->running++;
>        return;
>    }
>
> regards,
>
> Richard.