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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1E003C2D0C4 for ; Wed, 11 Dec 2019 03:22:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E9060214D8 for ; Wed, 11 Dec 2019 03:22:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726987AbfLKDWC (ORCPT ); Tue, 10 Dec 2019 22:22:02 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:7213 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726687AbfLKDWC (ORCPT ); Tue, 10 Dec 2019 22:22:02 -0500 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 86EDA17B335F7DBE9168; Wed, 11 Dec 2019 11:21:59 +0800 (CST) Received: from [127.0.0.1] (10.74.219.194) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.439.0; Wed, 11 Dec 2019 11:21:50 +0800 From: "chenxiang (M)" Subject: Failed to disable WCE for a SATA disk To: "axboe@kernel.dk" , Tejun Heo , "Martin K. Petersen" , Bart Van Assche CC: "linux-scsi@vger.kernel.org" , , Linuxarm , John Garry Message-ID: Date: Wed, 11 Dec 2019 11:21:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.74.219.194] X-CFilter-Loop: Reflected Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Hi, I encounter a issue related to libata and libsas. For hisi_sas driver, it uses libsas. When disable WCE with tool sdparm (sdparm --clear=WCE /dev/sda) for a SATA disk, it fails with error info from hardware (the error info indicates that the length of transfer data is conflicted with the direction of data, the length is 0 but the data of direction is from host to device). I check the process: When disable WCE, it sends pasthrough IO with sg_io , req->__data_len is not 0, and scsi_cmd->sc_data_direction = DMA_TO_DEVICE. But for the command (MODE_SELECT), qc->tf.protocol is set 0 (not ATA_PROT_DMA) in ->queuecommand() ->ata_sas_queuecmd()->ata_scsi_translate()->ata_scsi_mod_select_xlat()->ata_mselect_caching(), so it doesn't dma map ata sg in function ata_qc_issue(). While in function sas_ata_qc_issue()，it calcutes the length with the total sum of sg_dma_len(sg), as for the command it doesn't dma map ata sg, so the length is 0. Do we need to dma map ata sg for the command? Or is it really we need the data for the command MODE_SELECT? Thanks, Shawn