napi driver for multiport device with the only one dma channel - is it possible?

napi driver for multiport device with the only one dma channel - is it possible?

[Jan Petrous]

Hi,

am I understand it right that I can not use NAPI-powered design in case
when there is only one rx queue and one tx queue (only two
dma channels) usable for data transfer with the ethernet controller for
all interfaces (2 ports or more)?

I could imagine there would be possibility to declare for example rx
queue sharable between napi interfaces, but I was not able to find
anything like that.

I agree that it is a bit strange configuration but we have to support
such corner case (when other dma channels are used by independent
systems).

I seems like I have to create two drivers - one with napi, when at
least the same number of dma channels are free for use and second one
without napi (because of not enough dma channels).


Thanks.
/Jan

Re: napi driver for multiport device with the only one dma channel - is it possible?

[Stephen Hemminger]

On Thu, 13 Dec 2018 13:30:50 +0000
Jan Petrous <jan.petrous@nxp.com> wrote:

> Hi,
> 
> am I understand it right that I can not use NAPI-powered design in case
> when there is only one rx queue and one tx queue (only two
> dma channels) usable for data transfer with the ethernet controller for
> all interfaces (2 ports or more)?
> 
> I could imagine there would be possibility to declare for example rx
> queue sharable between napi interfaces, but I was not able to find
> anything like that.
> 
> I agree that it is a bit strange configuration but we have to support
> such corner case (when other dma channels are used by independent
> systems).
> 
> I seems like I have to create two drivers - one with napi, when at
> least the same number of dma channels are free for use and second one
> without napi (because of not enough dma channels).
> 
> 
> Thanks.
> /Jan

It is possible. Sky2 for some hardware has a single NAPI (on port 0)
and if the card is dual port the napi of port 0 is used by port 1.

Re: napi driver for multiport device with the only one dma channel - is it possible?

[Jan Petrous]

Hi Steven.

On Thu, 2018-12-13 at 10:18 -0800, Stephen Hemminger wrote:
> On Thu, 13 Dec 2018 13:30:50 +0000
> Jan Petrous <jan.petrous@nxp.com> wrote:
> 
> > Hi,
> > 
> > am I understand it right that I can not use NAPI-powered design in
> > case
> > when there is only one rx queue and one tx queue (only two
> > dma channels) usable for data transfer with the ethernet controller
> > for
> > all interfaces (2 ports or more)?
> > 
> > I could imagine there would be possibility to declare for example
> > rx
> > queue sharable between napi interfaces, but I was not able to find
> > anything like that.
> > 
> > I agree that it is a bit strange configuration but we have to
> > support
> > such corner case (when other dma channels are used by independent
> > systems).
> > 
> > I seems like I have to create two drivers - one with napi, when at
> > least the same number of dma channels are free for use and second
> > one
> > without napi (because of not enough dma channels).
> > 
> > 
> > Thanks.
> > /Jan
> 
> It is possible. Sky2 for some hardware has a single NAPI (on port 0)
> and if the card is dual port the napi of port 0 is used by port 1.

Thanks for the hint. It is exactly what I was searching for.

/Jan