From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88C4CC17443 for ; Sun, 10 Nov 2019 19:35:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A6EA20818 for ; Sun, 10 Nov 2019 19:35:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726896AbfKJTfZ (ORCPT ); Sun, 10 Nov 2019 14:35:25 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:41334 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726778AbfKJTfZ (ORCPT ); Sun, 10 Nov 2019 14:35:25 -0500 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id xAAJWegn062982; Sun, 10 Nov 2019 14:35:17 -0500 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 2w6be838yw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 10 Nov 2019 14:35:17 -0500 Received: from m0098393.ppops.net (m0098393.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id xAAJXEfi064039; Sun, 10 Nov 2019 14:35:16 -0500 Received: from ppma02dal.us.ibm.com (a.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.10]) by mx0a-001b2d01.pphosted.com with ESMTP id 2w6be838yn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 10 Nov 2019 14:35:16 -0500 Received: from pps.filterd (ppma02dal.us.ibm.com [127.0.0.1]) by ppma02dal.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id xAAJP597011453; Sun, 10 Nov 2019 19:35:15 GMT Received: from b01cxnp22036.gho.pok.ibm.com (b01cxnp22036.gho.pok.ibm.com [9.57.198.26]) by ppma02dal.us.ibm.com with ESMTP id 2w5n35j5x2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 10 Nov 2019 19:35:15 +0000 Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xAAJZFbC36897122 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 10 Nov 2019 19:35:15 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F0CC6112062; Sun, 10 Nov 2019 19:35:14 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 20BA7112063; Sun, 10 Nov 2019 19:35:14 +0000 (GMT) Received: from jarvis.ext.hansenpartnership.com (unknown [9.85.190.120]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Sun, 10 Nov 2019 19:35:13 +0000 (GMT) Message-ID: <1573414513.3230.4.camel@linux.ibm.com> Subject: Re: [PATCH] zorro_esp: increase maximum dma length to 65536 bytes From: James Bottomley To: Michael Schmitz , Kars de Jong , "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org, linux-m68k@vger.kernel.org Date: Sun, 10 Nov 2019 11:35:13 -0800 In-Reply-To: <6b914b12-cbc7-6fe6-7cba-3e89b2f6f19b@gmail.com> References: <20191109191400.8999-1-jongk@linux-m68k.org> <1573330351.3650.4.camel@linux.ibm.com> <6b914b12-cbc7-6fe6-7cba-3e89b2f6f19b@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-11-10_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=828 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1910280000 definitions=main-1911100194 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Sun, 2019-11-10 at 15:36 +1300, Michael Schmitz wrote: > All of the old board-specific drivers used a max transfer length of > 0x1000000, only the fastlane driver used 0xfffc. That lower limit > might be due to a DMA limitation on the fastlane board. We could > accommodate the different limit for this board by using a board- > specific dma_length_limit() callback... Sure, that implies the minimum dma burst length is 4 bytes ... > > case for any of the cards the zorro_esp drives, it might be better > > to lower the max length to 61440 (64k-4k) so the residual is a > > page. > > For the benefit of keeping the code simple, and avoid retesting the > fastlane board, that might indeed be the better solution. ... which means you don't have to lower the limit by 4k as I suggested, because I was being incredibly conservative about what the dma burst length might be, just use 0xfffc as the default. I think raising to 0x1000000 for boards which can support it is fine too if you want to add the extra logic to the driver. James