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 E5CA5C2BA83 for ; Fri, 7 Feb 2020 20:04:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCC08222C2 for ; Fri, 7 Feb 2020 20:04:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727347AbgBGUEa (ORCPT ); Fri, 7 Feb 2020 15:04:30 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:18578 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727012AbgBGUE3 (ORCPT ); Fri, 7 Feb 2020 15:04:29 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 017JxK1s147412; Fri, 7 Feb 2020 15:04:25 -0500 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xyhn5n8h6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 Feb 2020 15:04:24 -0500 Received: from m0098421.ppops.net (m0098421.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 017K0kKY005873; Fri, 7 Feb 2020 15:04:24 -0500 Received: from ppma04wdc.us.ibm.com (1a.90.2fa9.ip4.static.sl-reverse.com [169.47.144.26]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xyhn5n8gq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 Feb 2020 15:04:24 -0500 Received: from pps.filterd (ppma04wdc.us.ibm.com [127.0.0.1]) by ppma04wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id 017K4FWr005458; Fri, 7 Feb 2020 20:04:23 GMT Received: from b01cxnp22035.gho.pok.ibm.com (b01cxnp22035.gho.pok.ibm.com [9.57.198.25]) by ppma04wdc.us.ibm.com with ESMTP id 2xykc9yxph-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 Feb 2020 20:04:23 +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 017K4Nr448234900 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 7 Feb 2020 20:04:23 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 108E128065; Fri, 7 Feb 2020 20:04:23 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 939EE28059; Fri, 7 Feb 2020 20:04:22 +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 20:04:22 +0000 (GMT) Subject: Re: [PATCH] spi: Add FSI-attached SPI controller driver To: Andy Shevchenko Cc: Eddie James , 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> <90973143-bd0a-33cf-9eb8-a83be1a9b415@linux.vnet.ibm.com> From: Eddie James Message-ID: Date: Fri, 7 Feb 2020 14:04:22 -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_05:2020-02-07,2020-02-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 clxscore=1015 adultscore=0 mlxlogscore=999 bulkscore=0 spamscore=0 lowpriorityscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002070142 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/7/20 1:39 PM, Andy Shevchenko wrote: > On Fri, Feb 7, 2020 at 9:28 PM Eddie James wrote: >> 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: > ... > >>>>>>>> + 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. > Yes, I missed correction of the start address in memcpy(). Otherwise > it's still the same what I was talking about. I see now, yes, thanks. Do you think this is worth a v3? Perhaps put_unaligned is slightly more optimized than the loop but there is more memory copy with that way too. 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. >>> >>>>>>>> +}