From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tommy Christensen Subject: Re: [PATCH] 3c59x: read current link status from phy Date: Fri, 09 Sep 2005 00:39:18 +0200 Message-ID: <4320BD96.3060307@tpack.net> References: <200509080125.j881PcL9015847@hera.kernel.org> <431F9899.4060602@pobox.com> <1126184700.4805.32.camel@tsc-6.cph.tpack.net> <1126190554.4805.68.camel@tsc-6.cph.tpack.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------090202050309010401090008" Cc: Jeff Garzik , Linux Kernel Mailing List , Andrew Morton , Netdev List Return-path: To: Bogdan Costescu In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This is a multi-part message in MIME format. --------------090202050309010401090008 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Bogdan Costescu wrote: > I now understood what the problem was, so I'll put it in words for > posterity: the Link Status bit of the MII Status register needs to be > read twice to first clear the error state (link bit=0) after which the > bit reports the actual value of the link. From the manual: Yes, this is exactly the point. > But I still don't agree with your solution: you are reading the Status > register twice in all cases, which is wrong. What you want is to read it > a second time only after the link was marked as down: a simple check if > bit 2 of the Status register is 0, in which case you issue the second > read. This still means that there will be 2 reads if the link remains > down, but at least there is only 1 read for the case where the link is > up and remains up. I don't think this makes much of a difference in the big picture, but you're certainly right: let's not waste more cycles than we have to. Can we agree on the patch below? -Tommy --------------090202050309010401090008 Content-Type: text/plain; name="3c59x-carrier.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="3c59x-carrier.patch" [3c59x] Avoid blindly reading link status twice In order to spare some I/O operations, be more intelligent about when to read from the PHY. Pointed out by Bogdan Costescu. Signed-off-by: Tommy S. Christensen --- linux-2.6.13-git8/drivers/net/3c59x.c-orig Fri Sep 9 00:05:49 2005 +++ linux-2.6.13-git8/drivers/net/3c59x.c Fri Sep 9 00:13:55 2005 @@ -1889,7 +1889,9 @@ vortex_timer(unsigned long data) { spin_lock_bh(&vp->lock); mii_status = mdio_read(dev, vp->phys[0], 1); - mii_status = mdio_read(dev, vp->phys[0], 1); + if (!(mii_status & BMSR_LSTATUS)) + /* Re-read to get actual link status */ + mii_status = mdio_read(dev, vp->phys[0], 1); ok = 1; if (vortex_debug > 2) printk(KERN_DEBUG "%s: MII transceiver has status %4.4x.\n", --------------090202050309010401090008--