netdev - Re: [PATCH net 1/2] tg3: Fix for diasllow rx coalescing time to be 0

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Message-ID: <CACKFLikoKktanhxgaMeSA0NGmA6RiaBnxnCXUYfcssYWefdMVg@mail.gmail.com>
Date:	Wed, 3 Aug 2016 15:15:35 -0700
From:	Michael Chan <michael.chan@...adcom.com>
To:	Rick Jones <rick.jones2@....com>
Cc:	skallam <siva.kallam@...adcom.com>,
	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>,
	Prashant Sreedharan <prashant@...adcom.com>,
	Satish Baddipadige <satish.baddipadige@...adcom.com>
Subject: Re: [PATCH net 1/2] tg3: Fix for diasllow rx coalescing time to be 0

On Wed, Aug 3, 2016 at 9:04 AM, Rick Jones <rick.jones2@....com> wrote:
>
> Should anything then happen with:
>
>         /* No rx interrupts will be generated if both are zero */
>         if ((ec->rx_coalesce_usecs == 0) &&
>             (ec->rx_max_coalesced_frames == 0))
>                 return -EINVAL;
>
>
> which is the next block of code?  The logic there seems to suggest that it
> was intended to be able to have an rx_coalesce_usecs of 0 and rely on packet
> arrival to trigger an interrupt.  Presumably setting rx_max_coalesced_frames
> to 1 to disable interrupt coalescing.
>

I remember writing this block of code over 10 years ago for early
generations of the chip.  Newer chips seem to behave differently and
rx_coalesce_usecs can never be zero.  So this block can be removed now
that the condition can never be true.  We should probably leave a
comment there for future reference.