From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752167AbbLVHFI (ORCPT ); Tue, 22 Dec 2015 02:05:08 -0500 Received: from mx2.suse.de ([195.135.220.15]:42022 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751710AbbLVHFF (ORCPT ); Tue, 22 Dec 2015 02:05:05 -0500 Subject: Re: [PATCH v3 18/77] ncr5380: Eliminate USLEEP_WAITLONG delay To: Finn Thain , "James E.J. Bottomley" , Michael Schmitz , linux-m68k@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "Martin K. Petersen" References: <20151222011737.980475848@telegraphics.com.au> <20151222011742.905471269@telegraphics.com.au> From: Hannes Reinecke Message-ID: <5678F61E.4050905@suse.de> Date: Tue, 22 Dec 2015 08:05:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20151222011742.905471269@telegraphics.com.au> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/22/2015 02:17 AM, Finn Thain wrote: > Linux 2.1.105 introduced the USLEEP_WAITLONG delay, apparently "needed for > Mustek scanners". It is intended to stall the issue queue for 5 seconds. > There are a number of problems with this. > > 1. Only g_NCR5380 enables the delay, which implies that the other five > drivers using the NCR5380.c core driver remain incompatible with > Mustek scanners. > > 2. The delay is not implemented by atari_NCR5380.c, which is problematic > for re-unifying the two core driver forks. > > 3. The delay is implemented using NCR5380_set_timer() which makes it > unreliable. A new command queued by the mid-layer cancels the delay. > > 4. The delay is applied indiscriminately in several situations in which > NCR5380_select() returns -1. These are-- reselection by the target, > failure of the target to assert BSY, and failure of the target to > assert REQ. It's clear from the comments that USLEEP_WAITLONG is not > relevant to the reselection case. And reportedly, these scanners do > not disconnect. > > 5. atari_NCR5380.c was forked before Linux 2.1.105, so it was spared some > of the damage done to NCR5380.c. In this case, the atari_NCR5380.c core > driver was more standard-compliant and may not have needed any > workaround like the USLEEP_WAITLONG kludge. The compliance issue was > addressed in the previous patch. > > If these scanners still don't work, we need a better solution. Retrying > selection until EH aborts a command offers equivalent robustness. Bugs in > the existing driver prevent EH working correctly but this is addressed in > a subsequent patch. Remove USLEEP_WAITLONG. > > Signed-off-by: Finn Thain > > --- > drivers/scsi/NCR5380.c | 19 +++++-------------- > drivers/scsi/g_NCR5380.c | 1 - > 2 files changed, 5 insertions(+), 15 deletions(-) > > Index: linux/drivers/scsi/NCR5380.c > =================================================================== > --- linux.orig/drivers/scsi/NCR5380.c 2015-12-22 12:15:51.000000000 +1100 > +++ linux/drivers/scsi/NCR5380.c 2015-12-22 12:15:52.000000000 +1100 > @@ -468,10 +468,6 @@ static void NCR5380_print_phase(struct S > #ifndef USLEEP_POLL > #define USLEEP_POLL msecs_to_jiffies(200) > #endif > -#ifndef USLEEP_WAITLONG > -/* RvC: (reasonable time to wait on select error) */ > -#define USLEEP_WAITLONG USLEEP_SLEEP > -#endif > > /* > * Function : int should_disconnect (unsigned char cmd) > @@ -619,8 +615,8 @@ static void prepare_info(struct Scsi_Hos > "can_queue %d, cmd_per_lun %d, " > "sg_tablesize %d, this_id %d, " > "flags { %s%s%s%s}, " > -#if defined(USLEEP_POLL) && defined(USLEEP_WAITLONG) > - "USLEEP_POLL %lu, USLEEP_WAITLONG %lu, " > +#if defined(USLEEP_POLL) && defined(USLEEP_SLEEP) > + "USLEEP_POLL %lu, USLEEP_SLEEP %lu, " > #endif > "options { %s} ", > instance->hostt->name, instance->io_port, instance->n_io_port, > @@ -631,8 +627,8 @@ static void prepare_info(struct Scsi_Hos > hostdata->flags & FLAG_DTC3181E ? "DTC3181E " : "", > hostdata->flags & FLAG_NO_PSEUDO_DMA ? "NO_PSEUDO_DMA " : "", > hostdata->flags & FLAG_TOSHIBA_DELAY ? "TOSHIBA_DELAY " : "", > -#if defined(USLEEP_POLL) && defined(USLEEP_WAITLONG) > - USLEEP_POLL, USLEEP_WAITLONG, > +#if defined(USLEEP_POLL) && defined(USLEEP_SLEEP) > + USLEEP_POLL, USLEEP_SLEEP, > #endif > #ifdef AUTOPROBE_IRQ > "AUTOPROBE_IRQ " Wouldn't it make more sense to remove the USLEEP_WAITLONG completely? From what I can see it is meant to indicate that WAITLONG is enabled, but we've just removed that functionality... Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)