Hi Arnd,
On Mon, Nov 15, 2021 at 01:38:07PM +0100, Arnd Bergmann wrote:
On Mon, Nov 15, 2021 at 12:49 PM Laurent Pinchart wrote:
On Mon, Nov 15, 2021 at 11:21:30AM +0100, Arnd Bergmann wrote:
On Mon, Nov 15, 2021 at 10:14 AM Laurent Pinchart wrote:
On Mon, Nov 15, 2021 at 09:54:00AM +0100, Arnd Bergmann wrote:
@@ -1285,11 +1287,13 @@ static int xilinx_dpdma_config(struct dma_chan *dchan, spin_lock_irqsave(&chan->lock, flags);
/*
* Abuse the slave_id to indicate that the channel is part of a video* group.
* Abuse the peripheral_config to indicate that the channel is partIs it still an abuse, or is this now the right way to pass custom data to the DMA engine driver ?
It doesn't make the driver any more portable, but it's now being more explicit about it. As far as I can tell, this is the best way to pass data that cannot be expressed through the regular interfaces in DT and the dmaengine API.
Ideally there would be a generic way to pass this flag, but I couldn't figure out what this is actually doing, or whether there is a better way. Maybe Vinod has an idea.
I don't think we need a generic API in this case. The DMA engine is specific to the display device, I don't foresee a need to mix-n-match.
Right. I wonder if there is even a point in using the dmaengine API in that case, I think for other single-purpose drivers we tend to just integrate the functionality in the client driver. No point changing this now of course, but it does feel odd.
I agree, and that's what I would have done as well, if it wasn't for the fact that the DMA engine also supports a second client for audio. This isn't supported in upstream yet. We could still have created an ad-hoc solution, possibly based on the components framework, but the DMA engine subsystem wasn't a bad fit.
From my earlier reading of the driver, my impression was that this is just a memory-to-memory device, so it could be used that way as well, but does need a flag when working on the video memory. I couldn't quite make sense of that though.
It's only memory-to-device (video and audio). See figures 33-1 and 33-16 in https://www.xilinx.com/support/documentation/user_guides/ug1085-zynq-ultrasc...
/* * Use the peripheral_config to indicate that the channel is part * of a video group. This requires matching use of the custom * structure in each driver. */ pconfig = config->peripheral_config; if (WARN_ON(config->peripheral_size != 0 && config->peripheral_size != sizeof(*pconfig))) return -EINVAL;How about
if (WARN_ON(config->peripheral_config && config->peripheral_size != sizeof(*pconfig)))spin_lock_irqsave(&chan->lock, flags); if (chan->id <= ZYNQMP_DPDMA_VIDEO2 && config->peripheral_size == sizeof(*pconfig))And here you can test pconfig != NULL.
Good idea. Changed now, using 'if (pconfig)' without the '!= NULL' in both expressions.
Sounds good to me.