Re: [PATCH v4 10/15] dmaengine: ti: New driver for K3 UDMA - split#2: probe/remove, xlate and filter_fn

Vinod Koul
2019-11-12T05:34:48Z

On 11-11-19, 11:16, Peter Ujfalusi wrote:
>
>
> On 11/11/2019 7.33, Vinod Koul wrote:
> > On 01-11-19, 10:41, Peter Ujfalusi wrote:
> >
> >> +static bool udma_dma_filter_fn(struct dma_chan *chan, void *param)
> >> +{
> >> + struct psil_endpoint_config *ep_config;
> >> + struct udma_chan *uc;
> >> + struct udma_dev *ud;
> >> + u32 *args;
> >> +
> >> + if (chan->device->dev->driver != &udma_driver.driver)
> >> + return false;
> >> +
> >> + uc = to_udma_chan(chan);
> >> + ud = uc->ud;
> >> + args = param;
> >> + uc->remote_thread_id = args[0];
> >> +
> >> + if (uc->remote_thread_id & K3_PSIL_DST_THREAD_ID_OFFSET)
> >> + uc->dir = DMA_MEM_TO_DEV;
> >> + else
> >> + uc->dir = DMA_DEV_TO_MEM;
> >
> > Can you explain this a bit?
>
> The UDMAP in K3 works between two PSI-L endpoint. The source and
> destination needs to be paired to allow data flow.
> Source thread IDs are in range of 0x0000 - 0x7fff, while destination
> thread IDs are 0x8000 - 0xffff.
>
> If the remote thread ID have the bit 31 set (0x8000) then the transfer
> is MEM_TO_DEV and I need to pick one unused tchan for it. If the remote
> is the source then it can be handled by rchan.
>
> dmas = <&main_udmap 0xc400>, <&main_udmap 0x4400>;
> dma-names = "tx", "rx";
>
> 0xc400 is a destination thread ID, so it is MEM_TO_DEV
> 0x4400 is a source thread ID, so it is DEV_TO_MEM
>
> Even in MEM_TO_MEM case I need to pair two UDMAP channels:
> UDMAP source threads are starting at offset 0x1000, UDMAP destination
> threads are 0x9000+

Okay so a channel is set for a direction until teardown. Also this and
other patch comments are quite useful, can we add them here?

> Changing direction runtime is hardly possible as it would involve
> tearing down the channel, removing interrupts, destroying rings,
> removing the PSI-L pairing and redoing everything.

okay I would expect the prep_ to check for direction and reject the call
if direction is different.

--
~Vinod