From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Date: Tue, 03 Jun 2014 20:02:19 +0000 Subject: Re: [PATCH v2] sh_eth: use RNC mode for R8A7790/R87791 Message-Id: <538E29CB.4020008@cogentembedded.com> List-Id: References: <538CFA08.3010302@cogentembedded.com> In-Reply-To: <538CFA08.3010302@cogentembedded.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sh@vger.kernel.org Hello. On 06/03/2014 03:19 PM, Ben Dooks wrote: >>>>>>> Looks like the early SH2/3 SoCs didn't implement the whole >>>>>>> register. >>>>>>> Despite that, sh_eth_dev_init() always writes to this register... :-/ >>>>>>> So far, the RMCR.RNC bit was mostly set for the Gigabit-capable >>>>>>> controllers, however that rule wasn't strictly followed. Well, this >>>>>>> driver is still a mess, and it's hard to deal with it without the >>>>>>> necessary documentation. >>>>>> Why don't we therefore: >>>>>> 1) Skip the register write if the per-chip value is zero. >>>>> I rather thought about not writing when the register is not >>>>> implemented. >>>>> I'll probably look into this when I have time. >>>>>> 2) Add the RNC bit to all of the gigabit capable controllers. >>>>> I probably misspoke -- all the Gigabit controllers already have it >>>>> set, it's just that some 100 MBbps ones have it set, but most >>>>> don't. >>>> So these chips that do not implement the register, they only process >>>> one RX descriptor at a time until the interrupt handler re-enables >>>> DMA receive? >>> I just don't know. Looks like the driver is broken on SH2/3 even >>> more than >>> I thought: it always reads the EDRRR register in sh_eth_rx() trying to >>> understand if the reception has been stopped but that register doesn't >>> seem to >>> exist on SH2/3. Moreover, sh_eth_interrupt() reads EESR in order to >>> determine >>> the interrupt status but that register doesn't seem to exist on SH2/3 >>> either! >> OK, I've chased down the commit that broke SH2/3 support 3+ years >> ago; here it is: >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?idJ55530f38e4eeee3afb06093e81309138fe8360 >> All the registers I've mentioned did exist on SH2/3, they just got >> missed in the mapping arrays. > I suppose it would be a good idea to submit a patch to add these then. Not that I'm supposed to fix the old SH machines now but I've just posted the patch. :-) WBR, Sergei