From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752874AbbK2AqU (ORCPT ); Sat, 28 Nov 2015 19:46:20 -0500 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:42557 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752333AbbK2AqQ (ORCPT ); Sat, 28 Nov 2015 19:46:16 -0500 Date: Sun, 29 Nov 2015 11:46:03 +1100 (AEDT) From: Finn Thain To: Ondrej Zary cc: "James E.J. Bottomley" , Michael Schmitz , linux-m68k@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 22/71] ncr5380: Eliminate selecting state In-Reply-To: <201511290013.06581.linux@rainbow-software.org> Message-ID: References: <20151118083455.331768508@telegraphics.com.au> <201511262035.40920.linux@rainbow-software.org> <201511290013.06581.linux@rainbow-software.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 29 Nov 2015, Ondrej Zary wrote: > > [...] I think that this should solve the problem: > > Yes, it does! > > [ 48.119367] scsi host2: Generic NCR5380/NCR53C400 SCSI, io_port 0x0, n_io_port 0, base 0xd8000, irq 0, can_queue 16, cmd_per_lun 2, sg_tablesize 128, this_id 7, flags { NO_DMA_FIXUP }, options { AUTOPROBE_IRQ PSEUDO_DMA } > [ 49.715388] scsi 2:0:1:0: Direct-Access QUANTUM LP240S GM240S01X 4.6 PQ: 0 ANSI: 2 CCS That still takes about 1.6 seconds to scan a vacant bus ID. It should be more like 0.25 seconds. Did you have the entire patch series applied? The code presently in mainline spins for 500 iterations in the relevant busy-wait loop, with the comment, "8uS a cycle for the cpu access". That doesn't help me much. Does that refer to an ISA bus cycle? Or one iteration of the loop? Electrical conductance? If we knew how many loops_per_jiffy your machine gets, and your CONFIG_HZ value, we could figure out how long a chip register access takes (which might be 8 us). I'll try to figure out a similar timing for my Domex PCI card to see if there is some sort of compromise to be found. --