From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: Phy read timeout in ibm_new_emac driver Date: Wed, 16 Apr 2008 22:09:51 +1000 Message-ID: <1208347791.6958.279.camel@pasglop> References: <6a6049b80804160349q42120b4bs1c0db49ea5ad055d@mail.gmail.com> Reply-To: benh@kernel.crashing.org Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, ppc-dev To: M B Return-path: Received: from gate.crashing.org ([63.228.1.57]:54742 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759730AbYDPMKP (ORCPT ); Wed, 16 Apr 2008 08:10:15 -0400 In-Reply-To: <6a6049b80804160349q42120b4bs1c0db49ea5ad055d@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: > My Micrel/Kendin KSZ8721BT on my ppc405EP board needs one us longer to > finish. I was able to reproduce this all the time. So I wonder if the > timeout of 100us is defined by the MII standard, or by the author of > the driver? > If it's a standard I've still a bad feeling if we just correct the > timeout to 100us, maybe 110 should be fine. If it's not defined by the > standard, I would add 50% to the timeout. It won't slow down other > phys, but a scan on the phy bus might get slowed down. > Same applies for __emac_mdio_write. > > Oh and we could save a us by putting the udelay(1) after the if section ;-) Increasing the timeout is fine. In fact, EMAC specifically can sleep in it's MDIO access routines (it already takes mutexes) so maybe a good option here is to use longer sleeping delays and less iterations. Somebody knows off hand what the standard says the timeout should be ? I can check that tomorrow, I don't have it at hand right now and it's getting late but feel free to beat me to it :-) Cheers, Ben.