dma-trace: Allow DMA re-configuration

[ujfalusi]

The host will receive an error if it tries to re-configure the dtrace:

[ 22736132.117381] ( 28.645832) c0 hda-dma ..../intel/hda/hda-dma.c:489 ERROR hda-dmac: 4 no free channel 0
[ 22736147.377797] ( 15.260416) c0 dma-copy src/ipc/dma-copy.c:163 ERROR dma_copy_set_stream_tag(): dc->chan is NULL
[ 22736180.346545] ( 32.968750) c0 ipc src/ipc/ipc3/handler.c:805 ERROR ipc: failed to enable trace -22

Since we try to request an already used channel. If we skip the requesting
then we will fail with the configuration:

[ 31707957.542122] ( 27.447916) c0 dma-copy src/ipc/dma-copy.c:162 ERROR dma_copy_set_stream_tag(): already have chan for stream_tag 1
[ 31708021.917120] ( 64.375000) c0 hda-dma ..../intel/hda/hda-dma.c:539 ERROR hda-dmac: 4 channel 0 busy. dgcs 0x800000 status 5
[ 31708056.083785] ( 34.166664) c0 ipc src/ipc/ipc3/handler.c:805 ERROR ipc: failed to enable trace -16

To support the reconfiguration:
if we have DMA channel for dtrace, stop it to allow the reconfiguration.
In the unlikely case when the stream_id has changed, release the channel
as well and request a new one.

Tested with the SOF client kernel by rmmod and modprobe the dtrace client
during active audio playback to prevent the DSP to be turned off.

Signed-off-by: Peter Ujfalusi peter.ujfalusi@linux.intel.com

[marc-hb]

What is the simplest way to test this?

[ujfalusi]

What is the simplest way to test this?

my wip branch is kept up to date with sof-dev:
https://github.com/ujfalusi/sof-linux/tree/peter/sof%2Fauxiliary_bus_wip_take3

Build it, reboot if needed.
start audio playback (aplay -Dhw:0,0 -fdat /dev/urandom)
while it is running:
rmmod snd_sof_dma_trace
modprobe snd_sof_dma_trace

And repeat the module removal/insert

[ujfalusi]

Changes since v1:

• Add a patch to implement cleanup on error in dma_trace_start()
• Use mtrace_printf() to print a warning in case of DMA channel reconfiguration

[lgirdwood]

Hapy to merge alongside #4849 or this one first. Let me know.

[lgirdwood]

Seems CI is stuck. Restart it.

[lgirdwood]

SOFCI TEST

[marc-hb]

Could adding some reference to the channel in the log be helpful?

[ujfalusi]

Changes since v2:

• print the stream_tag if the channel is used, also print the change in stream_tag (unlikely)

[lyakh]

just use else if to avoid repeating err == 0?

[ujfalusi]

Yes, that is a cleaner way.

[ujfalusi]

Changes since v3:

• use else if to avoid re-testing for err == 0 when verifying the current and new stream_tag.