* Tony Lindgren <t...@atomide.com> [170118 16:50]:
> At least with the cppi41 dma, size 1 in dma transfers will just wait
> until the device is disconnected. And it also seems that enumerating
> a USB stick with a hub can take a USB reset with smallish size in
> transfers.
>
> This causes timeouts in cppi41 dma runtime PM.
>
> Fix the issue by adding a minimum size of 16 which is based on my
> obeservations on BeagleBone to make enumerating more reliable.
>
> Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
> Signed-off-by: Tony Lindgren <t...@atomide.com>
> ---
> drivers/usb/musb/musb_host.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
> --- a/drivers/usb/musb/musb_host.c
> +++ b/drivers/usb/musb/musb_host.c
> @@ -743,7 +743,14 @@ static void musb_ep_program(struct musb *musb, u8 epnum,
>
> musb_ep_select(mbase, epnum);
>
> - if (is_out && !len) {
> + /*
> + * Skip dma for zero sized out and small in transfers.
> + * At least cppi41 in dma will just hang with size of 1 until the
> + * device is connected. For sizes 8 and less it seems to take a
> + * long time to complete. Let's use minimum size of 16 to avoid
> + * tiny in DMA transfers.
> + */
> + if ((is_out && !len) || (!is_out && (len < 16))) {
> use_dma = 0;
> csr = musb_readw(epio, MUSB_TXCSR);
> csr &= ~MUSB_TXCSR_DMAENAB;
Uh I think this needs a separate check to not mess with the TXCSR
for in transfers.
Regards,
Tony
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