Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 30 May 2022 10:06:39 +0200 | Subject | Re: [PATCH] dmaengine: add verification of DMA_INTERRUPT capability for dmatest |
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Hi Dave, Vinod,
On Wed, Apr 13, 2022 at 12:58 AM Dave Jiang <dave.jiang@intel.com> wrote: > Looks like I forgot to add DMA_INTERRUPT cap setting to the idxd driver and > dmatest is still working regardless of this mistake. Add an explicit check > of DMA_INTERRUPT capability for dmatest to make sure the DMA device being used > actually supports interrupt before the test is launched and also that the > driver is programmed correctly. > > Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Thanks for your patch, which is now commit a8facc7b988599f8 ("dmaengine: add verification of DMA_INTERRUPT capability for dmatest") upstream.
> --- a/drivers/dma/dmatest.c > +++ b/drivers/dma/dmatest.c > @@ -675,10 +675,16 @@ static int dmatest_func(void *data) > /* > * src and dst buffers are freed by ourselves below > */ > - if (params->polled) > + if (params->polled) { > flags = DMA_CTRL_ACK; > - else > - flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT; > + } else { > + if (dma_has_cap(DMA_INTERRUPT, dev->cap_mask)) { > + flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT; > + } else { > + pr_err("Channel does not support interrupt!\n"); > + goto err_pq_array; > + } > + } > > ktime = ktime_get(); > while (!(kthread_should_stop() || > @@ -906,6 +912,7 @@ static int dmatest_func(void *data)
Shimoda-san reports that this commit breaks dmatest on rcar-dmac. Like most DMA engine drivers, rcar-dmac does not set the DMA_INTERRUPT capability flag, hence dmatest now fails to start:
dmatest: Channel does not support interrupt!
To me, it looks like the new check is bogus, as I believe it confuses two different concepts:
1. Documentation/driver-api/dmaengine/provider.rst says:
- DMA_INTERRUPT
- The device is able to trigger a dummy transfer that will generate periodic interrupts
2. In non-polled mode, dmatest sets DMA_PREP_INTERRUPT. include/linux/dmaengine.h says:
* @DMA_PREP_INTERRUPT - trigger an interrupt (callback) upon completion of * this transaction
As dmatest uses real transfers, I think it does not depend on the ability to use interrupts from dummy transfers.
Do you agree? Thanks!
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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