Re: [PATCH v5] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

["Måns Rullgård" <mans@mansr.com>]

David Miller <davem@davemloft.net> writes:

> From: Måns Rullgård <mans@mansr.com>
> Date: Wed, 11 Nov 2015 19:09:19 +0000
>
>> David Miller <davem@davemloft.net> writes:
>> 
>>> From: Måns Rullgård <mans@mansr.com>
>>> Date: Wed, 11 Nov 2015 18:25:05 +0000
>>>
>>>> If the TX DMA channel is idle when start_xmit is called, it can be
>>>> started immediately.  Checking the DMA status and starting it if
>>>> idle has to be done atomically somehow.
>>>
>>> ->ndo_start_xmit() is guaranteed to be invoked atomically, protected
>>> by the TX queue spinlock.
>> 
>> Yes, but the DMA needs to be restarted from some other context if it was
>> busy when start_xmit checked.
>
> Then you can probably use the TXQ lock in the interrupt handler just for
> that.

That seems a bit heavy-handed when the critical section for this is only
a tiny part of the start_xmit function.

-- 
Måns Rullgård
mans@mansr.com