From: Jose Abreu <joabreu@xxxxxxxxxxxx> Date: Sep/25/2019, 12:41:04 (UTC+00:00) > From: David Miller <davem@xxxxxxxxxxxxx> > Date: Sep/25/2019, 12:33:53 (UTC+00:00) > > > From: Jose Abreu <Jose.Abreu@xxxxxxxxxxxx> > > Date: Wed, 25 Sep 2019 10:44:53 +0000 > > > > > From: David Miller <davem@xxxxxxxxxxxxx> > > > Date: Sep/24/2019, 20:45:08 (UTC+00:00) > > > > > >> From: Thierry Reding <thierry.reding@xxxxxxxxx> > > >> Date: Fri, 20 Sep 2019 19:00:34 +0200 > > >> > > >> Also, you're now writing to the high 32-bits unconditionally, even when > > >> it will always be zero because of 32-bit addressing. That looks like > > >> a step backwards to me. > > > > > > Don't agree. As per previous discussions and as per my IP knowledge, if > > > EAME is not enabled / not supported the register can still be written. > > > This is not fast path and will not impact any remaining operation. Can > > > you please explain what exactly is the concern about this ? > > > > > > Anyway, this is an important feature for performance so I hope Thierry > > > re-submits this once -next opens and addressing the review comments. > > > > Perhaps I misunderstand the context, isn't this code writing the > > descriptors for every packet? > > No, its just setting up the base address for the descriptors which is > done in open(). The one that's in the fast path is the tail address, > which is always the lower 32 bits. Oops, sorry. Indeed it's done in refill operation in function dwmac4_set_addr() for rx/tx which is fast path so you do have a point that I was not seeing. Thanks for bringing this up! Now, the point would be: a) Is it faster to have an condition check in dwmac4_set_addr(), or b) Always write to descs the upper 32 bits. Which always exists in the IP and is a standard write to memory. --- Thanks, Jose Miguel Abreu
