03.02.2020 14:37, Jon Hunter пишет:

On 01/02/2020 15:13, Dmitry Osipenko wrote:

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31.01.2020 17:22, Dmitry Osipenko пишет:

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31.01.2020 12:02, Jon Hunter пишет:

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On 30/01/2020 20:04, Dmitry Osipenko wrote:

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The tegra_dma_stop() should put RPM anyways, which is missed in yours
sample. Please see handle_continuous_head_request().

Yes and that is deliberate. The cyclic transfers the transfers *should*
not stop until terminate_all is called. The tegra_dma_stop in
handle_continuous_head_request() is an error condition and so I am not
sure it is actually necessary to call pm_runtime_put() here.

But then tegra_dma_stop() shouldn't unset the "busy" mark.

True.

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I'm also finding the explicit get/put a bit easier to follow in the
code, don't you think so?

I can see that, but I was thinking that in the case of cyclic transfers,
it should only really be necessary to call the get/put at the beginning
and end. So in my mind there should only be two exit points which are
the ISR handler for SG and terminate_all for SG and cyclic.

Alright, I'll update this patch.

Hmmm ... I am wondering if we should not mess with that and leave how
you have it.

I took another look and seems my current v6 should be more correct because:

1. If "busy" is unset in tegra_dma_stop(), then the RPM should be put
there since tegra_dma_terminate_all() won't put RPM in this case:

	if (!tdc->busy)
		goto skip_dma_stop;

2. We can't move the "busy" unsetting into the terminate because then
tegra_dma_stop() will be invoked twice. Although, one option could be to
remove the tegra_dma_stop() from the error paths of
handle_continuous_head_request(), but I'm not sure that this is correct
to do.

Jon, I realized that my v6 variant is wrong too because
tegra_dma_terminate_all() -> tdc->isr_handler() will put RPM, and thus,
the RPM enable-count will be wrecked in this case.

Did you see my other suggestion to move the pm_runtime_put() outside of
tegra_dma_stop?

Yes, but seems I skimmed too quickly through the lines and failed to
recognize the point you made.

There are only a few call sites for tegra_dma_stop and
so if we call pm_runtime_put() after calling tegra_dma_stop this should
simplify matters.

This is somewhat similar to what I made in the v7. Instead of adding
pm_runtime_put() after each tegra_dma_stop(), I removed the
tegra_dma_stop().

Looking at it once again, perhaps indeed it will be better to leave the
relevant tegra_dma_stop() in place (the irrelevant could be removed).

Please take a look at the v7, I'll drop the "[PATCH v7 13/19] dmaengine:
tegra-apb: Don't stop cyclic DMA in a case of error condition" and make
v8 after yours review of the v7. Thanks in advance!