Re: [PATCH v2 6/6] test/dmadev: add tests for stopping and restarting dev

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Feb 15, 2023 at 09:59:06AM +0800, fengchengwen wrote:
> On 2023/1/17 1:37, Bruce Richardson wrote:
> > Validate device operation when a device is stopped or restarted.
> > 
> > The only complication - and gap in the dmadev ABI specification - is
> > what happens to the job ids on restart. Some drivers reset them to 0,
> > while others continue where things left off. Take account of both
> > possibilities in the test case.
> > 
> > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com> ---
> > app/test/test_dmadev.c | 46 ++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 46 insertions(+)
> > 
> > diff --git a/app/test/test_dmadev.c b/app/test/test_dmadev.c index
> > de787c14e2..8fb73a41e2 100644 --- a/app/test/test_dmadev.c +++
> > b/app/test/test_dmadev.c @@ -304,6 +304,48 @@
> > test_enqueue_copies(int16_t dev_id, uint16_t vchan) ||
> > do_multi_copies(dev_id, vchan, 0, 0, 1); }
> >  
> > +static int +test_stop_start(int16_t dev_id, uint16_t vchan) +{ +	/*
> > device is already started on input, should be (re)started on output */
> > + +	uint16_t id = 0; +	enum rte_dma_status_code status =
> > RTE_DMA_STATUS_SUCCESSFUL; + +	/* - test stopping a device works
> > ok, +	 * - then do a start-stop without doing a copy +	 *
> > - finally restart the device +	 * checking for errors at each
> > stage, and validating we can still copy at the end.  +	 */ +	if
> > (rte_dma_stop(dev_id) < 0) +		ERR_RETURN("Error stopping
> > device\n"); + +	if (rte_dma_start(dev_id) < 0) +
> > ERR_RETURN("Error restarting device\n"); +	if (rte_dma_stop(dev_id) <
> > 0) +		ERR_RETURN("Error stopping device after restart (no
> > jobs executed)\n"); + +	if (rte_dma_start(dev_id) < 0) +
> > ERR_RETURN("Error restarting device after multiple stop-starts\n"); + +
> > /* before doing a copy, we need to know what the next id will be it
> > should +	 * either be: +	 * - the last completed job before start if
> > driver does not reset id on stop +	 * - or -1 i.e. next job is 0, if
> > driver does reset the job ids on stop +	 */ +	if
> > (rte_dma_completed_status(dev_id, vchan, 1, &id, &status) != 0) +
> > ERR_RETURN("Error with rte_dma_completed_status when no job done\n"); +
> > id += 1; /* id_count is next job id */ +	if (id != id_count && id !=
> > 0) +		ERR_RETURN("Unexpected next id from device after
> > stop-start. Got %u, expected %u or 0\n", +				id,
> > id_count);
> 
> Hi Bruce,
> 
> Suggest add a warn LOG to identify the id was not reset zero.  So that
> new driver could detect break ABI specification.
> 
Not sure that that is necessary. The actual ABI, nor the doxygen docs,
doesn't specify what happens to the values on doing stop and then start. My
thinking was that it should continue numbering as it would be equivalent to
suspend and resume, but other drivers appear to treat it as a "reset". I
suspect there are advantages and disadvantages to both schemes. Until we
decide on what the correct behaviour should be - or decide to allow both -
I don't think warning is the right thing to do here.

/Bruce