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 EB01DC2BA83 for ; Fri, 7 Feb 2020 19:28:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC4C020661 for ; Fri, 7 Feb 2020 19:28:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727065AbgBGT2t (ORCPT ); Fri, 7 Feb 2020 14:28:49 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:11742 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726900AbgBGT2s (ORCPT ); Fri, 7 Feb 2020 14:28:48 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 017JEwWv091196; Fri, 7 Feb 2020 14:28:43 -0500 Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 2y0ktsu67d-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 Feb 2020 14:28:43 -0500 Received: from m0098419.ppops.net (m0098419.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 017JFNjU092205; Fri, 7 Feb 2020 14:28:42 -0500 Received: from ppma02dal.us.ibm.com (a.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.10]) by mx0b-001b2d01.pphosted.com with ESMTP id 2y0ktsu672-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 Feb 2020 14:28:42 -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 017JPobF027215; Fri, 7 Feb 2020 19:28:41 GMT Received: from b01cxnp22035.gho.pok.ibm.com (b01cxnp22035.gho.pok.ibm.com [9.57.198.25]) by ppma02dal.us.ibm.com with ESMTP id 2xykca5kvv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 Feb 2020 19:28:41 +0000 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 017JSf0354591802 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 7 Feb 2020 19:28:41 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1008D2805A; Fri, 7 Feb 2020 19:28:41 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 913DA28059; Fri, 7 Feb 2020 19:28:40 +0000 (GMT) Received: from [9.41.103.158] (unknown [9.41.103.158]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 7 Feb 2020 19:28:40 +0000 (GMT) Subject: Re: [PATCH] spi: Add FSI-attached SPI controller driver To: Andy Shevchenko , Eddie James Cc: linux-spi , Linux Kernel Mailing List , Mark Brown , Joel Stanley , Andrew Jeffery References: <1580328504-436-1-git-send-email-eajames@linux.ibm.com> <29f6cc86-69ca-bc88-b6ae-2b1a24c0dae3@linux.vnet.ibm.com> <744f0019-8656-eec1-cb9a-7e70cd042587@linux.ibm.com> From: Eddie James Message-ID: <90973143-bd0a-33cf-9eb8-a83be1a9b415@linux.vnet.ibm.com> Date: Fri, 7 Feb 2020 13:28:40 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-07_04:2020-02-07,2020-02-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 mlxlogscore=999 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 spamscore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002070139 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/5/20 9:51 AM, Andy Shevchenko wrote: > On Tue, Feb 4, 2020 at 6:06 PM Eddie James wrote: >> On 2/4/20 5:02 AM, Andy Shevchenko wrote: >>> On Mon, Feb 3, 2020 at 10:33 PM Eddie James wrote: >>>> On 1/30/20 10:37 AM, Andy Shevchenko wrote: >>>>> On Wed, Jan 29, 2020 at 10:09 PM Eddie James wrote: > ... > >>>>>> + struct device *dev; >>>>> Isn't fsl->dev the same? >>>>> Perhaps kernel doc to explain the difference? >>>> No, it's not the same, as dev here is the SPI controller. I'll add a >>>> comment. >>> Why to have duplication then? >> >> Nothing is being duplicated, the two variables are storing entirely >> different information, both of which are necessary for each SPI >> controller that this driver is driving. > Oh, I see now, thanks! > > ... > >>>>>> + for (i = 0; i < num_bytes; ++i) >>>>>> + rx[i] = (u8)((in >> (8 * ((num_bytes - 1) - i))) & 0xffULL); >>>>> Redundant & 0xffULL part. >>>>> >>>>> Isn't it NIH of get_unalinged_be64 / le64 or something similar? >>>> No, these are shift in/out operations. The read register will also have >>>> previous operations data in them and must be extracted with only the >>>> correct number of bytes. >>> Why not to call put_unaligned() how the tail in this case (it's 0 or >>> can be easily made to be 0) will affect the result? >> >> The shift-in is not the same as any byte-swap or unaligned operation. >> For however many bytes we've read, we start at that many bytes >> left-shifted in the register and copy out to our buffer, moving right >> for each next byte... I don't think there is an existing function for >> this operation. > For me it looks like > > u8 tmp[8]; > > put_unaligned_be64(in, tmp); > memcpy(rx, tmp, num_bytes); > > put_unaligned*() is just a method to unroll the value to the u8 buffer. > See, for example, linux/unaligned/be_byteshift.h implementation. Unforunately it is not the same. put_unaligned_be64 will take the highest 8 bits (0xff00000000000000) and move it into tmp[0]. Then 0x00ff000000000000 into tmp[1], etc. This is only correct for this driver IF my transfer is 8 bytes. If, for example, I transfer 5 bytes, then I need 0x000000ff00000000 into tmp[0], 0x00000000ff000000 into tmp[1], etc. So I think my current implementation is correct. Thanks, Eddie > >>>>>> + return num_bytes; >>>>>> +} >>>>>> +static int fsi_spi_data_out(u64 *out, const u8 *tx, int len) >>>>>> +{ >>>>> Ditto as for above function. (put_unaligned ...) >>> Ditto. >> >> I don't understand how this could work for transfers of less than 8 >> bytes, any put_unaligned would access memory that it doesn't own. > Ditto. > >>>>>> +}