From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932520AbbLVNhM (ORCPT ); Tue, 22 Dec 2015 08:37:12 -0500 Received: from mx2.suse.de ([195.135.220.15]:39683 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932293AbbLVNhH (ORCPT ); Tue, 22 Dec 2015 08:37:07 -0500 Subject: Re: [PATCH v3 18/77] ncr5380: Eliminate USLEEP_WAITLONG delay To: Finn Thain References: <20151222011737.980475848@telegraphics.com.au> <20151222011742.905471269@telegraphics.com.au> <5678F61E.4050905@suse.de> Cc: "James E.J. Bottomley" , Michael Schmitz , linux-m68k@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "Martin K. Petersen" From: Hannes Reinecke Message-ID: <567951FF.1020203@suse.de> Date: Tue, 22 Dec 2015 14:37:03 +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: 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 01:38 PM, Finn Thain wrote: > > On Tue, 22 Dec 2015, Hannes Reinecke wrote: > >> 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... > > Actually, this patch does remove USLEEP_WAITLONG completely. It does not > remove USLEEP_POLL and USLEEP_SLEEP. In patch 25, the USLEEP_POLL and > USLEEP_SLEEP stuff is replaced by an algorithm that sleeps while polling. > > You are right that adding USLEEP_SLEEP to this snprintf() is a change that > doesn't really belong here. But since I was changing those lines anyway, > it seemed like a good time to fix a mistake I made when I first added the > snprintf() and wrote "USLEEP_POLL, USLEEP_WAITLONG" instead of > "USLEEP_POLL, USLEEP_SLEEP". > > Shall I revise this patch? That will affect patch 25. Or perhaps I should > add the snprintf() change in the commit log? > > Thanks for your review. > Na, that's fine. The entire thing got removed in a later patch, so no worries. Reviewed-by: Hannes Reinecke 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)