Re: [PATCH] usb: gadget: u_ether: remove interrupt throttling

[Felipe Balbi <felipe.balbi@linux.intel.com>]

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Hi,

Peter Chen <hzpeterchen@gmail.com> writes:
>> Peter Chen <hzpeterchen@gmail.com> writes:
>> > On Wed, Nov 02, 2016 at 11:22:54AM -0400, David Miller wrote:
>> >> From: Peter Chen <hzpeterchen@gmail.com>
>> >> Date: Wed, 2 Nov 2016 14:02:02 +0800
>> >> 
>> >> > Felipe, it may increase cpu utilization since more interrupts will be there,
>> >> > it may affect the SoC which has lower cpu frequency. This code existed
>> >> > many years, why this problem has only reported at dwc3 recently?
>> >> 
>> >> It's a bug, and it's going to cause TCP sockets to potentially hang.
>> >> 
>> >
>> > For some controllers, it is, so we need to add parameter for user
>> > to see if interrupt migration is supported or not.
>> 
>> not for some controller, for ALL networking drivers.
>> 
>> > But just like some ethernet controllers, some USB controllers support
>> > hardware timeout mechanism which interrupt will be triggered after
>> > some uFrame occurs if the transaction has completed but not required
>> > to interrupt, it is used to support interrupt migration like ethernet.
>> 
>> you're missing the point. What Dave Miller is saying is that it's ALWAYS
>> a bug to delay completion of SKBs. The only thing you're doing with
>> chipidea is delaying interrupt by up to 125us; which is still a bug from
>> the point of view of the networking layer, but it's more difficult to
>> perceive any problems because of the short time where interrupt is
>> delayed.
>> 
>
> If it is ALWAYS a bug to delay completion of SKBs, how the local
> ethernet driver designs interrupt migration?

what driver are you talking about? Which "local" ethernet driver?

Also, do you mean 'moderation' instead of 'migration?

-- 
balbi

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