Re: Getting to the bottom of the Dreamcast DMA issue

[Paul M. <le...@li...>]

On Sun, Jul 15, 2007 at 07:09:02PM +0100, Adrian McMenamin wrote:
> It appears it is not the sh_dmac code which is to blame, but the
> pvr2_dma code. If I fix the build to exclude pvr2_dma.c, the Dreamcast
> will boot with CONFIG_NR_ONCHIP_DMA_CHANNELS set correctly (ie to 4)
> 
CONFIG_NR_ONCHIP_DMA_CHANNELS should be 4 for this, yes.
CONFIG_NR_DMA_CHANNELS should be 9, as per the Kconfig entry.

> Plainly the pvr code is broken when it tries to take channel 4, not sure
> why though, will have a deeper look.
> 
How do you reach that conclusion? The pvr code is requesting the first
channel of the pvr2 DMAC. SH DMAC channels are mapped to virtual channels
0 - 3, pvr2 at 4, andthe G2 channels above that. It's all ordering
dependent.

While there might be some problems in the channel management, you're
barking up the wrong tree here. This stuff worked fine before, and the
driver has undergone zero changes in terms of the DMA code since then.