Hi Dave, Vinod,
On Wed, Apr 13, 2022 at 12:58 AM Dave Jiang <dave.jiang@xxxxxxxxx> 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@xxxxxxxxx>
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@xxxxxxxxxxxxxx
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
