Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 6 Jul 2001 14:26:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 6 Jul 2001 14:26:10 -0400 Received: from h131s117a129n47.user.nortelnetworks.com ([47.129.117.131]:25475 "HELO pcard0ks.ca.nortel.com") by vger.kernel.org with SMTP id ; Fri, 6 Jul 2001 14:25:59 -0400 Message-ID: <3B4602BA.91C5DAD3@nortelnetworks.com> Date: Fri, 06 Jul 2001 14:26:02 -0400 From: Chris Friesen X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.3-custom i686) X-Accept-Language: en MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Cc: becker@scyld.com, root@chaos.analogic.com Subject: why this 1ms delay in mdio_read? (cont'd from "are ioctl calls supposed to take this long?") In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org The beginning of mdio_read() in tulip.c goes like this: static int mdio_read(struct device *dev, int phy_id, int location) { struct tulip_private *tp = (struct tulip_private *)dev->priv; int i; int read_cmd = (0xf6 << 10) | (phy_id << 5) | location; int retval = 0; long ioaddr = dev->base_addr; long mdio_addr = ioaddr + CSR9; if (tp->chip_id == LC82C168) { int i = 1000; outl(0x60020000 + (phy_id<<23) + (location<<18), ioaddr + 0xA0); inl(ioaddr + 0xA0); inl(ioaddr + 0xA0); while (--i > 0) if ( ! ((retval = inl(ioaddr + 0xA0)) & 0x80000000)) return retval & 0xffff; return 0xffff; } if (tp->chip_id == COMET) { if (phy_id == 1) { if (location < 7) return inl(ioaddr + 0xB4 + (location<<2)); else if (location == 17) return inl(ioaddr + 0xD0); else if (location >= 29 && location <= 31) return inl(ioaddr + 0xD4 + ((location-29)<<2)); } return 0xffff; } mdelay(1); /* One ms delay... */ ...rest of code... The chip I'm using is the DEC 21143, which means that we skip over the two conditional blocks, so the first thing that happens when we call this is to wait around doing nothing for a millisecond. Is there some subtle reason why we would want to wait around for a millisecond before doing anything? Thanks for your help, Chris -- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/