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=-17.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 34B02C07E9B for ; Sat, 10 Jul 2021 08:14:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 180C4613AB for ; Sat, 10 Jul 2021 08:14:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232103AbhGJIRO (ORCPT ); Sat, 10 Jul 2021 04:17:14 -0400 Received: from mail-eopbgr00102.outbound.protection.outlook.com ([40.107.0.102]:48110 "EHLO EUR02-AM5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S230009AbhGJIRL (ORCPT ); Sat, 10 Jul 2021 04:17:11 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=jkg1maZHlQa331PBxlH10HsEAN6IGy/wbbdazPB8erWIaJN9wKWX6ZC4a2Re11n87nvPzZRzjtWYAzHxV5VaprZQHY5W8aLWPgfjpCtG9UY4Pl2xbtGQJeQxjgJEY2oXQSHvq4SrogMMljIZEGrZbFKP84H4hrfCHLqVUFOUFK7RpbXKzUjkBum7jtuiKDG8IIIL+JMiB+ovq6rRrjbf4FqDyLVKoLl4fd6bz51ts30Y5VtJlmf9o8ntdi/7YDFwdgM33eyMTHiq03R5T5RwDsf1TFpZFnja+/GnOAh4+uVXGxOMJ+ud5JkKivpq8fwA2+Lp32JhpAkF+0hcNwvduQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=4+TesGfYmJRGQUFN1XDt/Fy7MvYRwzxqwxk9vrY0FUk=; b=hE/w7PCoOQ9SoSpbENkLMQFZiRIQnqOwkyXxjlT/jxzecxo1VZ4lCDx1M8y9+0dzFZnfHOtq8fH3PqEMRiu3FfgtNZu2ZipC2R+sDwznjboAYBNEI+Lb2Ohh80WjXqOFuDojc6iNK2OzR47I4FKQiabI21bP5hKmRM9CVx8E7I+ACgJvdKH1/3K6Fzml47HuhKbPMQutjYKGFgrpTcfcKBA9Jt7eQ+esRgb5Si7Yb/DMiJf+7ZvF9JuG4RS39LnBKS3/cf7q83Lu5MKSwoPJW0felp0mISXQywXnsFPu2OJQwHCeUcGST6lY4g6DvHXtzQ8IM4jOcVR9oNTlYJNWQA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=axentia.se; dmarc=pass action=none header.from=axentia.se; dkim=pass header.d=axentia.se; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=axentia.se; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=4+TesGfYmJRGQUFN1XDt/Fy7MvYRwzxqwxk9vrY0FUk=; b=PFn6ovgBjBV+3JobCgPPMEYxFCS2nZMHTjl0P8FV1BOsYbZTzcHb3BiAUsSsPe9cKcXMTeVQxw8bqAgORCbPuAj6+Ro5AQawX78pfgV9lFxsftHyt4o2D7cHtU7ALX+Wtvo6WHiXka/QXX0Q9vXQm/j6P3XbnNCQm2GPfdYqUEk= Authentication-Results: kernel.org; dkim=none (message not signed) header.d=none;kernel.org; dmarc=none action=none header.from=axentia.se; Received: from DB8PR02MB5482.eurprd02.prod.outlook.com (2603:10a6:10:eb::29) by DB3PR0202MB3418.eurprd02.prod.outlook.com (2603:10a6:8:d::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4287.23; Sat, 10 Jul 2021 08:14:23 +0000 Received: from DB8PR02MB5482.eurprd02.prod.outlook.com ([fe80::14ca:a41:2218:3578]) by DB8PR02MB5482.eurprd02.prod.outlook.com ([fe80::14ca:a41:2218:3578%6]) with mapi id 15.20.4287.035; Sat, 10 Jul 2021 08:14:23 +0000 Subject: Re: [PATCH v4 05/10] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support To: Liam Beguin , jic23@kernel.org, lars@metafoo.de, pmeerw@pmeerw.net Cc: linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, robh+dt@kernel.org References: <20210706160942.3181474-1-liambeguin@gmail.com> <20210706160942.3181474-6-liambeguin@gmail.com> <4be51a74-9913-291a-9dac-422ac23da3ea@axentia.se> From: Peter Rosin Organization: Axentia Technologies AB Message-ID: <353ceae9-ad7a-3175-d764-a9e590d3e8d3@axentia.se> Date: Sat, 10 Jul 2021 10:14:20 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: sv-SE Content-Transfer-Encoding: 7bit X-ClientProxiedBy: HE1PR05CA0201.eurprd05.prod.outlook.com (2603:10a6:3:f9::25) To DB8PR02MB5482.eurprd02.prod.outlook.com (2603:10a6:10:eb::29) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.13.3] (85.229.94.233) by HE1PR05CA0201.eurprd05.prod.outlook.com (2603:10a6:3:f9::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4308.20 via Frontend Transport; Sat, 10 Jul 2021 08:14:23 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 511d16c2-bb5a-47b5-4d1e-08d9437aba13 X-MS-TrafficTypeDiagnostic: DB3PR0202MB3418: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DB8PR02MB5482.eurprd02.prod.outlook.com;PTR:;CAT:NONE;SFS:(396003)(366004)(346002)(376002)(136003)(39830400003)(8936002)(6486002)(8676002)(16576012)(36756003)(186003)(956004)(38100700002)(316002)(478600001)(26005)(36916002)(31696002)(31686004)(66556008)(2906002)(2616005)(66946007)(86362001)(53546011)(66476007)(5660300002)(4326008)(45980500001)(43740500002);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?Tzl0ME91Wm9KQ1lRZXFMMlRNWXFlV0NudmpmVEo4UGhqNS9ZR0tvMW1ZWHgy?= =?utf-8?B?dmgyN2FxdEJyeEZCcHlRSmhxajYwRHJwdjZyZk1MMmwyeXpsMzFUbE9MUEw4?= =?utf-8?B?UjhGNlpWQWhvck5Ka2ZHRjlHSG84OHdTa2dhUnByZmRQeER0Rml0MVJPOFlv?= =?utf-8?B?M1BlOUk4OHVaL21YRzE2VUtSZUVHcG1vSEZtdnhGTmgwczNaMWxhbDNkMGwz?= =?utf-8?B?YnpKeEJJYXZXTlJiaVZTNTc4RWw5dTVTcUZDWDB0Q3RYNVhoNksvVXdYbnBw?= =?utf-8?B?MUdGS1d0d0N5bHovVm55Q0k1dys3MDJCK2hFbXJEVGZkbjNIVFdrUnp1cU9V?= =?utf-8?B?K3NCdyt1ejVtTlc1SzMvNkJkZzJmYWpKUnAyK011QzhqaGZXK2xMeUpGRko4?= =?utf-8?B?cUdHd3BiZ292MjhreVFrOTFZNmQ4TmFwL3lWdGNmVVM1MklrZHlseVYzVldN?= =?utf-8?B?RGluTkVndFBZNS9yUzF4cGxPZitNeWpMY3J3Y3pvMXBUL0w2c0FRMXFqTGwz?= =?utf-8?B?bUtJUXROdUQ2ODkxZ0dQYjBYNStZT3ZJV0FGaWpiZ2cwWFRSTVdZRVJwQmJq?= =?utf-8?B?M0RQTm53MnJ2TUo5Zmhnd2o2UkF3aVBqNWtFTGtYTVJCbzJwbXI3WGFZaGJi?= =?utf-8?B?NkwrZzV2Y3hqUDJyTlJOZzRrSkxoakszdEtydHFreCtNajk2V3NNc1VHT1hi?= =?utf-8?B?VFYzWWkwR0s1V0ZrZVFKZXg2dFVqVTVDdVpZekpsTG01YXAvY01STjRXdHZk?= =?utf-8?B?SzRrd005Tnk0dXc3RHFDSWkzcVRVRzlQTENCR1QwVENOaWxpSHNyNkR3aHRq?= =?utf-8?B?ZXpYdmF0SlJEaEhDTkxYazEweHl1Zjg0V05nd3JlUTY2NTJvL1NZSmU1RDRQ?= =?utf-8?B?Vy80b3RjUWxKQktWRys1NllhanBVd05FTEs2aFdHdmYrdFpjTU1SN3NzME1y?= =?utf-8?B?VTJFSjNkcC96Q3lSMDFkRnl4QlVNU1MwOXZPd1BtVjlGRlRXdnFHQ0hwMmRW?= =?utf-8?B?MlREbE90dUxqK2pvN1JhL2p5UzhuYVpUQmM0MkMveWVBWm1MZFZOdGFTUkoy?= =?utf-8?B?eldUR2EwNXp0UDZYNEwrNzZmL0F2SG9tbEJQU01kdFhnQmxVOVp0b3l4L1Zz?= =?utf-8?B?TjNqeVliY3FoNjJVUmZwbGhlTERvTUN1Mk5WdzRVNFE4azF2Wm1FQ2tyUGww?= =?utf-8?B?bDE2N0ZFRlE2bGcwbTl4ZCtXYnB1TEtBSnBaaTBzaWlMTng0NGM5dEhLdURn?= =?utf-8?B?VXE1QnV1WDN0dzhXUjNRdlZqNzlTYmJGaHhZcnVDalRjRTkrZ2lnOTdYeHMr?= =?utf-8?B?ZVp0ZWw4UG9xcUdFajlBbjhXZXgydWlSbVVDQm9kVFdsWHpKWFVTZ09HL3o1?= =?utf-8?B?SG1rK3g3S0QxcEpFZEdZS1FMM3VaVFpFZHQwa1NUNjVOT0plb2wvRk1MWmVn?= =?utf-8?B?aWwwMDVHSzRpZjNGaGpsb25sQUhka2tRNUtwK2UzdzBHZVBVWmxnTzNSbWRo?= =?utf-8?B?Q1Y0K1BNNkk4S0xCbC9Dcm9OOGtqZmJ6WFlzQXhDcW5BSFlXUCt5UDZxd1Za?= =?utf-8?B?Q0V0Mzh1YVF5Z2ptT05QUjZIcXViQXZreUIvTnA3MGlsekdvaE1OZEN5US9a?= =?utf-8?B?VHIxY0sxc0Zqd3pwTXFTSmNlMHJYeHc3V0hDSndDVC92Q2FCb1hYS3lBTnp4?= =?utf-8?B?WTdTdll3bzJ6VnNybHN2UDg2ZEdVNU83N1VKME9PQTBEYUxZYkEwREFJck0y?= =?utf-8?Q?7dEvEP21Y/n8HDv84sTGHAfrt9/rV8iHepixPAt?= X-OriginatorOrg: axentia.se X-MS-Exchange-CrossTenant-Network-Message-Id: 511d16c2-bb5a-47b5-4d1e-08d9437aba13 X-MS-Exchange-CrossTenant-AuthSource: DB8PR02MB5482.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jul 2021 08:14:23.7733 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4ee68585-03e1-4785-942a-df9c1871a234 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: QL4u9l2b/h2fw1Ug9CrM3Q4rMPDfV57RhW8k/x16WvIf56dLTYn9yk+v3StWl+dp X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB3PR0202MB3418 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-07-09 21:30, Liam Beguin wrote: > On Fri Jul 9, 2021 at 12:29 PM EDT, Peter Rosin wrote: >> >> >> On 2021-07-06 18:09, Liam Beguin wrote: >>> From: Liam Beguin >>> >>> Add IIO_VAL_INT_PLUS_{NANO,MICRO} scaling support. >>> Scale the integer part and the decimal parts individually and keep the >>> original scaling type. >>> >>> Signed-off-by: Liam Beguin >>> --- >>> drivers/iio/afe/iio-rescale.c | 8 ++++++++ >>> 1 file changed, 8 insertions(+) >>> >>> diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c >>> index ba3bdcc69b16..1d0e24145d87 100644 >>> --- a/drivers/iio/afe/iio-rescale.c >>> +++ b/drivers/iio/afe/iio-rescale.c >>> @@ -89,7 +89,15 @@ static int rescale_read_raw(struct iio_dev *indio_dev, >>> do_div(tmp, 1000000000LL); >>> *val = tmp; >>> return ret; >>> + case IIO_VAL_INT_PLUS_NANO: >>> + case IIO_VAL_INT_PLUS_MICRO: >>> + tmp = (s64)*val * rescale->numerator; >>> + *val = div_s64(tmp, rescale->denominator); >>> + tmp = (s64)*val2 * rescale->numerator; >>> + *val2 = div_s64(tmp, rescale->denominator); >> > > Hi Peter, > >> Hi! >> >> You are losing precision, and you are not mormalising after the >> calculation. > > Can you elaborate a little on what you mean here? > > Do you mean that I should make sure that *val2, the PLUS_{NANO,MICRO} > part, doesn't contain an integer part? And if so transfer that part back > to *val? Yes. On 32-bit, you will easily wrap, especially for PLUS_NANO. You'd only need a scale factor of 10 or so and a fractional part above .5 to hit the roof (10 * 500000000 > 2^32). But I also mean that you are losing precision when you are scaling the integer part and the fractional part separately. That deserves at least a comment, but ideally it should be handled correctly. >> I think it's better to not even attempt this given that the results can >> be >> really poor. > > Unfortunatelly, I'm kinda stuck with this as some of my ADC use these > types. Ok. Crap. :-) Cheers, Peter