Using the loop feature of the DMA controller on MPC8544 DS
timur at FREESCALE.COM
Thu Mar 13 02:58:21 EST 2008
Sebastian Siewior wrote:
> I have here a MPC8544 DS board and I tried to utilise the dma
> controller. For the transfers I need set the [S|D]AHE bit in the Mode
> Register. This seems to be implemented but is currently unused in the
Which driver? Zhang's DMA driver?
I haven't looked at Zhang's driver, but I just spotted this code:
new_fsl_chan->toggle_ext_start = fsl_chan_toggle_ext_start;
new_fsl_chan->toggle_ext_pause = fsl_chan_toggle_ext_pause;
new_fsl_chan->set_src_loop_size = fsl_chan_set_src_loop_size;
new_fsl_chan->set_dest_loop_size = fsl_chan_set_dest_loop_size;
(Don't let the missing "break" from FSL_DMA_IP_85XX fool you)
So it looks like there already is a way to set the SAHE and DAHE bits. I guess
this is what you mean by "seems to be implemented but is currently unused"?
> I haven't found a way how to set this bit except globally for
> the whole channel.
Well, the SAHE bit is part of the MR register, so it can only apply to a whole
channel. This is a hardware limitation.
> Is it possible to solve this nicely except dedicating one channel for
> such an operation?
Linux kernel developer at Freescale
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