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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 5F246C43219 for ; Wed, 1 May 2019 17:11:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E80F208C3 for ; Wed, 1 May 2019 17:11:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=impinj.com header.i=@impinj.com header.b="jNSlPJSY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726019AbfEARLz (ORCPT ); Wed, 1 May 2019 13:11:55 -0400 Received: from mail-eopbgr770113.outbound.protection.outlook.com ([40.107.77.113]:61102 "EHLO NAM02-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726005AbfEARLz (ORCPT ); Wed, 1 May 2019 13:11:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=impinj.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=kojW7S+AlG1rx3CFD8ID9aPv2p0VvWWrcMoljH3m8Ik=; b=jNSlPJSYueMMqpo7dHLXaFUPCgdqrFHuXreClNhB3Z7G0ihqQFLpFXTIK/FIhyR/JIW8Dl2HXe/RPbBqCN4B0TQzvznh+sl6srsoZKHzSN5JFRJ5Kj0s4SXaCM/sdKFY18eZ226zKG2BiBMtcofFgi1tlOQjlgZNYS2E1oO/1VI= Received: from MWHPR0601MB3708.namprd06.prod.outlook.com (10.167.236.38) by MWHPR0601MB3596.namprd06.prod.outlook.com (10.167.236.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.1856.10; Wed, 1 May 2019 17:11:50 +0000 Received: from MWHPR0601MB3708.namprd06.prod.outlook.com ([fe80::2d6d:7e4b:d2ff:5e29]) by MWHPR0601MB3708.namprd06.prod.outlook.com ([fe80::2d6d:7e4b:d2ff:5e29%3]) with mapi id 15.20.1856.008; Wed, 1 May 2019 17:11:44 +0000 From: Trent Piepho To: "alexandre.belloni@bootlin.com" CC: "patrice.chotard@st.com" , "linux-rtc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] rtc: st-lpc: remove unnecessary check Thread-Topic: [PATCH] rtc: st-lpc: remove unnecessary check Thread-Index: AQHU/5H32hcx4X+jhEK8dI4HvkdrpqZVSbiAgAEKhICAAC6FgA== Date: Wed, 1 May 2019 17:11:44 +0000 Message-ID: <1556730703.31309.53.camel@impinj.com> References: <20190430201834.12634-1-alexandre.belloni@bootlin.com> <1556663479.31309.36.camel@impinj.com> <20190501142513.GK11339@piout.net> In-Reply-To: <20190501142513.GK11339@piout.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=tpiepho@impinj.com; x-originating-ip: [216.207.205.253] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 5f998f5b-d709-4b3a-6e6f-08d6ce58165b x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600141)(711020)(4605104)(2017052603328)(7193020);SRVR:MWHPR0601MB3596; x-ms-traffictypediagnostic: MWHPR0601MB3596: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8882; x-forefront-prvs: 00246AB517 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(396003)(346002)(39850400004)(136003)(366004)(376002)(189003)(199004)(91956017)(68736007)(186003)(71190400001)(6246003)(478600001)(71200400001)(446003)(26005)(2501003)(86362001)(53936002)(229853002)(11346002)(6512007)(2616005)(476003)(76116006)(73956011)(66476007)(25786009)(8936002)(2906002)(486006)(54906003)(5640700003)(81156014)(66556008)(6916009)(36756003)(305945005)(6116002)(5660300002)(64756008)(66446008)(3846002)(99286004)(2351001)(66066001)(103116003)(6506007)(14454004)(14444005)(81166006)(102836004)(6486002)(8676002)(66946007)(256004)(7736002)(6436002)(316002)(4326008)(76176011);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR0601MB3596;H:MWHPR0601MB3708.namprd06.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A:1; received-spf: None (protection.outlook.com: impinj.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: CdNHVVc3M3BSSAHRBa9grt07cs2ZjPhftO1uO/+0uYkQPei6up/y+ihObIZGm0EqdY588gXnLBtSe4GydW8sim1scm58cRInN4FnSEZ8KKIoFMUrhsoOjp6hdK/xJUpv8p7arWHc0DY/BttQiC4AVyqT9RT/NtiGii4sNUNoSXiKf9/WlGSYqFXBpS78MiQvOdubKRksVnuIbxb+TlPghL1ai47nPH0IoHiEtgCepWbNPqTtJigZgn+h1hndMaTa+h2WBbfaKumCzPsLflsDkjxg+2p+YNavAGzC0BQVbnwGn7XEEfBr0tZ9TXNamnnTC4qauUn36hhwjMwK5DuUF5Stic3UaJ8rqn9g4B1MDAUNIXX7lKTi5kRzM0oFY0gUN7QG1qkYKhgTYB7ZdWwBgVjAXIwMCUBv9VzPOy/a3EA= Content-Type: text/plain; charset="utf-8" Content-ID: <49FCA81B3B0C5042BD02E5EC95515723@namprd06.prod.outlook.com> Content-Transfer-Encoding: base64 MIME-Version: 1.0 X-OriginatorOrg: impinj.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5f998f5b-d709-4b3a-6e6f-08d6ce58165b X-MS-Exchange-CrossTenant-originalarrivaltime: 01 May 2019 17:11:44.6117 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 6de70f0f-7357-4529-a415-d8cbb7e93e5e X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR0601MB3596 Sender: linux-rtc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rtc@vger.kernel.org T24gV2VkLCAyMDE5LTA1LTAxIGF0IDE2OjI1ICswMjAwLCBBbGV4YW5kcmUgQmVsbG9uaSB3cm90 ZToNCj4gT24gMzAvMDQvMjAxOSAyMjozMToxOSswMDAwLCBUcmVudCBQaWVwaG8gd3JvdGU6DQo+ ID4gT24gVHVlLCAyMDE5LTA0LTMwIGF0IDIyOjE4ICswMjAwLCBBbGV4YW5kcmUgQmVsbG9uaSB3 cm90ZToNCj4gPiA+IFRoZSBSVEMgY29yZSBhbHJlYWR5IGVuc3VyZXMgdGhlIGFsYXJtIGlzIHNl dCB0byBhIHRpbWUgaW4gdGhlIGZ1dHVyZSwgaXQNCj4gPiA+IGlzIG5vdCBuZWNlc3NhcnkgdG8g Y2hlY2sgYWdhaW4gaW4gdGhlIGRyaXZlci4NCj4gPiANCj4gPiBNeSByZWFkaW5nIG9mIHRoZSBy dGMgY29yZSBjb2RlIGlzIHRoYXQgaXQgY2hlY2tzIGlmIHRoZSBhbGFybSBpcyBpbg0KPiA+IHRo ZSBmdXR1cmUgKnR3aWNlKiBiZWZvcmUgaGFuZGluZyBvZmYgdGhlIHNldCBjYWxsIHRvIHRoZSBk cml2ZXIsIHdoaWNoDQo+ID4gcG9zc2libHkgY2hlY2tzIGEgM3JkIHRpbWUgKGFzIHNlZW4gaGVy ZSkuDQo+ID4gDQo+ID4gSG93ZXZlciwgYWxsIHRoZXNlIGNoZWNrcyBhcmUgZG9uZSAqYmVmb3Jl KiBzZXR0aW5nIHRoZSBhbGFybS4gIEl0DQo+ID4gc3RpbGwgcG9zc2libGUgdG8gaGF2ZSBhIHJh Y2UgYW5kIHNldCB0aGUgYWxhcm0gYWZ0ZXIgdGhlIHRpbWUgaGFzDQo+ID4gYWxyZWFkeSBwYXNz ZWQsIGluIHdoaWNoIGNhc2UgdGhlIGFsYXJtIHdpbGwgbmV2ZXIgZmlyZS4NCj4gPiANCj4gDQo+ IEkgYWdyZWUgdGhlIGNvcmUgbmVlZCB0byBoYW5kbGUgdGhhdCBwb3NzaWJsZSByYWNlIGJldHRl ciBhbmQgdGhpcyBpcw0KPiBzb21ldGhpbmcgSSdtIHBsYW5uaW5nIHRvIHdvcmsgb24uDQo+IA0K PiA+IFRoZSB3YXkgdG8gZml4IHRoZSByYWNlIHdvdWxkIGJlIHRvIGhhdmUgdGhlIGRyaXZlciBj aGVjayB0aGUgYWxhcm0NCj4gPiAqYWZ0ZXIqIHNldHRpbmcgaXQuICBJbiBwcmVjaXNlbHkgdGhp cyBvcmRlciwgZG8gdGhlc2Ugc3RlcHM6DQo+ID4gDQo+ID4gMS4gU2V0IGFsYXJtIGluIFJUQywg dG8gVGFsYXJtDQo+ID4gMi4gR2V0IHRpbWUgZnJvbSBSVEMsIGFzIFRjdXJyZW50DQo+ID4gMy4g R2V0IGFsYXJtIHN0YXR1cyBmcm9tIFJUQw0KPiA+IA0KPiA+IElmIFRhbGFybSA8IFRjdXJyZW50 LCBhbGFybSB3YXMgc2V0IHRvIGZ1dHVyZSB0aW1lLCBubyBlcnJvcg0KPiANCj4gVGhpcyBzaG91 bGQgYmUgVGFsYXJtID4gVGN1cnJlbnQsIHJpZ2h0Pw0KDQpZZXMuICBJIHdyb3RlIHRoYXQgYmFj a3dhcmQuDQoNCj4gPiBFbHNlDQo+ID4gICBJZiBzdGF0dXMgPT0gZmlyZWQsIGFsYXJtIHdhcyBz ZXQgYW5kIGhhcyBzaW5jZSBmaXJlZCwgbm8gZXJyb3INCj4gPiAgIEVsc2Ugc3RhdHVzID09IG5v dCBmaXJlZCwgYWxhcm0gd2FzIHNldCBpbiBwYXN0LCBFSU5WQUwNCj4gPiANCj4gPiBUaGlzIHNo b3VsZCBiZSByYWNlIGZyZWUuDQo+ID4gDQo+ID4gDQo+ID4gPiAgDQo+ID4gPiAtCS8qIEludmFs aWQgYWxhcm0gdGltZSAqLw0KPiA+ID4gLQlpZiAobm93X3NlY3MgPiBhbGFybV9zZWNzKQ0KPiA+ ID4gLQkJcmV0dXJuIC1FSU5WQUw7DQo+ID4gPiAtDQo+ID4gPiAgCW1lbWNweSgmcnRjLT5hbGFy bSwgdCwgc2l6ZW9mKHN0cnVjdCBydGNfd2thbHJtKSk7DQo+ID4gPiAgDQo+ID4gPiAgCS8qIE5v dyBtYW55IHNlY3MgdG8gZmlyZSAqLw0KPiA+IA0KPiA+ICAgICAgICAgYWxhcm1fc2VjcyAtPSBu b3dfc2VjczsNCj4gPiAgICAgICAgIGxwYSA9ICh1bnNpZ25lZCBsb25nIGxvbmcpYWxhcm1fc2Vj cyAqIHJ0Yy0+Y2xrcmF0ZTsNCj4gPiANCj4gPiBXaGlsZSBpdCdzIHRydWUgdGhlIHRpbWUgd291 bGRuJ3Qgbm9ybWFsbHkgYmUgaW4gcGFzdCwgaXQgc3RpbGwgcmFjZXMsDQo+ID4gYXMgZGVzY3Jp YmUgYWJvdmUuIEluIHRoYXQgY2FzZSwgdGhlIG1hdGggaGVyZSB1bmRlcmZsb3dzIGFsYXJtX3Nl Y3MsDQo+ID4gc28gaXQgcHJvYmFibHkgc3RpbGwgbWFrZXMgc2Vuc2UgdG8gY2hlY2suDQo+IA0K PiBJIGNhbid0IGJlbGlldmUgeW91IGNhbiBwb3NzaWJseSBoYXZlIG1vcmUgdGhhbiBvbmUgc2Vj b25kIGJldHdlZW4gdGhlDQo+IGNoZWNrIGluIHRoZSBjb3JlIGFuZCB0aGUgY2hlY2sgaW4gdGhl IGRyaXZlciwgaXQgZG9lc24ndCBtYWtlIG11Y2gNCj4gc2Vuc2UgdG8gY2hlY2ssIGV2ZW4gaW4g dGhlIGN1cnJlbnQgc3RhdGUgb2YgdGhlIGNvcmUuDQoNCkl0J3MgY2VydGFpbmx5IHBvc3NpYmxl IHRvIGhhdmUgbXVsdGlwbGUgc2Vjb25kcyBwYXNzLiAgRm9yIGFuIGV4dGVybmFsDQpkZXZpY2Ug b3ZlciBTUEkgb3IgSTJDLCBvbmUgaGFzIHRvIHdhaXQgZm9yIHRoZSBidXMgdG8gYmVjb21lIGZy ZWUuIA0KQW5kIG9uIFNQSSB0aGF0IHJlcXVpcmVzIHRoZSBrZXJuZWwgdGhyZWFkIHJ1bm5pbmcg dGhlIGJ1cyB0byBiZSANCnNjaGVkdWxlZC4gIEp1c3QgcHV0IGluIHNvbWUgcmVhbC10aW1lIHRh c2tzIGFuZCBtYXliZSBhIGJpZyB0cmFuc2Zlcg0KdG8gYSBmbGFzaCBjaGlwIGFuZCBpdCBjb3Vs ZCBiZSBhIHdoaWxlIGJlZm9yZSB0aGF0IGhhcHBlbnMuDQoNCkkgZG9uJ3QgdGhpbmsgdGhpcyBk ZXZpY2UgaGFzIHRoYXQgaXNzdWUgYXMgSSBkb24ndCB0aGluayBpdCdzDQpleHRlcm5hbC4gIEFu ZCBldmVyIGZvciBhIGRldmljZSBvbiBhbiBleHRlcm5hbCBidXMsIGRlbGF5cyA+IDEgc2Vjb25k DQphcmUgdW5saWtlbHkuICBQb3NzaWJsZSwgYnV0IHVubGlrZWx5Lg0KDQpZb3UgY2FuIGFsc28g Z2V0IHRoZW0gd2hlbiBMaW51eCBpcyBydW5uaW5nIHVuZGVyIGEgaHlwZXJ2aXNvciwgaS5lLiBh DQpMaW51eCBWTS4gIEJ1dCBhbHNvIHNvbWV0aGluZyBsaWtlIGFuIE5NSSBhbmQgQUNQSSBCSU9T LiAgSWYgdGhlIExpbnV4DQpndWVzdCBpcyBub3Qgc2NoZWR1bGVkIHRvIHJ1biBmb3Igd2hpbGUg YW55dGhpbmcgdGhhdCBpcyBzdXBwb3NlZCB0byBiZQ0KYmFzZWQgb24gcmVhbCB0aW1lLCBsaWtl IHRoZSB2YWx1ZSByZXR1cm5lZCBieSBhbiBSVEMsIHdpbGwgc3RpbGwNCmFkdmFuY2UuICBJdCBp cyBwb3NzaWJsZSB0aGF0IG11bHRpcGxlIHNlY29uZHMgZWxhcHNlIGZyb20gdGhlIGd1ZXN0DQpD UFUgZXhlY3V0aW5nIG9uZSBpbnN0cnVjdGlvbiB0byB0aGUgbmV4dC4NCg0KQnV0IGV2ZW4gaWdu b3JpbmcgdGhhdCwgZG9lcyBpdCByZXF1aXJlID4gMSBzZWNvbmQgdG8gZWxhcHNlLiAgQ2FuJ3Qg aXQNCmhhcHBlbiB3aGVuIHRoZSBjbG9jayB0aWNrcyBmcm9tIG9uZSBzZWNvbmQgdG8gdGhlIG5l eHQsIHdoaWNoIGhhcHBlbnMNCmVmZmVjdGl2ZWx5IGluc3RhbnRseT8NCg0KSWYgdGhlIHRpbWUg ZnJvbSB0aGUgY2hlY2sgdG8gdGhlIHRpbWUgd2hlbiB0aGUgYWxhcm0gaXMgc2V0IGlzIDENCm1p Y3Jvc2Vjb25kLCBhbmQgdGhlIHRpbWUgdGhpcyBjYWxsIHRvIHNldCB0aGUgYWxhcm0gaXMgbWFk ZSBpcw0KcmFuZG9tbHkgZG9uZSBhbmQgbm90IHN5bmNocm9uaXplZCB0byB0aGUgUlRDLCB0aGVu IGlzbid0IHRoZXJlIGEgMSBvdXQNCm9mIDEgbWlsbGlvbiBjaGFuY2UgKDEgbWljcm9zZWNvbmQg LyAxIHNlY29uZCksIHRoYXQgdGhlIG9uY2UgcGVyDQpzZWNvbmQgY2xvY2sgdGljayB3aWxsIGhp dCBvdXIgMSB1cyB3aW5kb3c/ 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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 73781C43219 for ; Wed, 1 May 2019 17:12:06 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 41D1220645 for ; Wed, 1 May 2019 17:12:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="rkJdTE88"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=impinj.com header.i=@impinj.com header.b="jNSlPJSY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 41D1220645 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=impinj.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Content-ID:In-Reply-To: References:Message-ID:Date:Subject:To:From:Reply-To:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rxnl4m3ujdj7W9zPfxwsxz6jE17NQFeStNrFxG0bgAQ=; b=rkJdTE88m0MnA7 eSFkd1qhQIJoOdkgfjIuh/i6lKaVtC84Oao1ZzR0DWm6qiAl99q4iySEPwIII7qRPLUri7ZqV+mV+ h7JMBGLYRB29EQX60Xy5kJA9bgrPpHeMT4wOQ+NT7Jlc2xSDEN93bvI90l1eAjaCHkr3sK70npufA 4EivYTQoy1n2bjrWH5/sQuK7qfoqlEEPxEyZHGX4O5NnMJ0GiVekCHj6t2brKKtJE6DCFXrDec09c LHv6NMzeypqDVwkk0Oy+c+RNMh4EDIOVDfFYKAjQjwA/uWhy/TPJEp95kjkG6N7Y2D4tcs31Ui+8r mhWBkWnEbdwDpbuoQq9w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hLsly-0004yv-53; Wed, 01 May 2019 17:11:58 +0000 Received: from mail-sn1nam02on071d.outbound.protection.outlook.com ([2a01:111:f400:fe44::71d] helo=NAM02-SN1-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hLslu-0004xc-RH for linux-arm-kernel@lists.infradead.org; Wed, 01 May 2019 17:11:57 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=impinj.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=kojW7S+AlG1rx3CFD8ID9aPv2p0VvWWrcMoljH3m8Ik=; b=jNSlPJSYueMMqpo7dHLXaFUPCgdqrFHuXreClNhB3Z7G0ihqQFLpFXTIK/FIhyR/JIW8Dl2HXe/RPbBqCN4B0TQzvznh+sl6srsoZKHzSN5JFRJ5Kj0s4SXaCM/sdKFY18eZ226zKG2BiBMtcofFgi1tlOQjlgZNYS2E1oO/1VI= Received: from MWHPR0601MB3708.namprd06.prod.outlook.com (10.167.236.38) by MWHPR0601MB3596.namprd06.prod.outlook.com (10.167.236.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.1856.10; Wed, 1 May 2019 17:11:50 +0000 Received: from MWHPR0601MB3708.namprd06.prod.outlook.com ([fe80::2d6d:7e4b:d2ff:5e29]) by MWHPR0601MB3708.namprd06.prod.outlook.com ([fe80::2d6d:7e4b:d2ff:5e29%3]) with mapi id 15.20.1856.008; Wed, 1 May 2019 17:11:44 +0000 From: Trent Piepho To: "alexandre.belloni@bootlin.com" Subject: Re: [PATCH] rtc: st-lpc: remove unnecessary check Thread-Topic: [PATCH] rtc: st-lpc: remove unnecessary check Thread-Index: AQHU/5H32hcx4X+jhEK8dI4HvkdrpqZVSbiAgAEKhICAAC6FgA== Date: Wed, 1 May 2019 17:11:44 +0000 Message-ID: <1556730703.31309.53.camel@impinj.com> References: <20190430201834.12634-1-alexandre.belloni@bootlin.com> <1556663479.31309.36.camel@impinj.com> <20190501142513.GK11339@piout.net> In-Reply-To: <20190501142513.GK11339@piout.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=tpiepho@impinj.com; x-originating-ip: [216.207.205.253] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 5f998f5b-d709-4b3a-6e6f-08d6ce58165b x-microsoft-antispam: BCL:0; PCL:0; RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600141)(711020)(4605104)(2017052603328)(7193020); SRVR:MWHPR0601MB3596; x-ms-traffictypediagnostic: MWHPR0601MB3596: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8882; x-forefront-prvs: 00246AB517 x-forefront-antispam-report: SFV:NSPM; SFS:(10019020)(396003)(346002)(39850400004)(136003)(366004)(376002)(189003)(199004)(91956017)(68736007)(186003)(71190400001)(6246003)(478600001)(71200400001)(446003)(26005)(2501003)(86362001)(53936002)(229853002)(11346002)(6512007)(2616005)(476003)(76116006)(73956011)(66476007)(25786009)(8936002)(2906002)(486006)(54906003)(5640700003)(81156014)(66556008)(6916009)(36756003)(305945005)(6116002)(5660300002)(64756008)(66446008)(3846002)(99286004)(2351001)(66066001)(103116003)(6506007)(14454004)(14444005)(81166006)(102836004)(6486002)(8676002)(66946007)(256004)(7736002)(6436002)(316002)(4326008)(76176011); DIR:OUT; SFP:1102; SCL:1; SRVR:MWHPR0601MB3596; H:MWHPR0601MB3708.namprd06.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1; received-spf: None (protection.outlook.com: impinj.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: CdNHVVc3M3BSSAHRBa9grt07cs2ZjPhftO1uO/+0uYkQPei6up/y+ihObIZGm0EqdY588gXnLBtSe4GydW8sim1scm58cRInN4FnSEZ8KKIoFMUrhsoOjp6hdK/xJUpv8p7arWHc0DY/BttQiC4AVyqT9RT/NtiGii4sNUNoSXiKf9/WlGSYqFXBpS78MiQvOdubKRksVnuIbxb+TlPghL1ai47nPH0IoHiEtgCepWbNPqTtJigZgn+h1hndMaTa+h2WBbfaKumCzPsLflsDkjxg+2p+YNavAGzC0BQVbnwGn7XEEfBr0tZ9TXNamnnTC4qauUn36hhwjMwK5DuUF5Stic3UaJ8rqn9g4B1MDAUNIXX7lKTi5kRzM0oFY0gUN7QG1qkYKhgTYB7ZdWwBgVjAXIwMCUBv9VzPOy/a3EA= Content-ID: <49FCA81B3B0C5042BD02E5EC95515723@namprd06.prod.outlook.com> MIME-Version: 1.0 X-OriginatorOrg: impinj.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5f998f5b-d709-4b3a-6e6f-08d6ce58165b X-MS-Exchange-CrossTenant-originalarrivaltime: 01 May 2019 17:11:44.6117 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 6de70f0f-7357-4529-a415-d8cbb7e93e5e X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR0601MB3596 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190501_101154_939675_64182E8B X-CRM114-Status: GOOD ( 24.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-rtc@vger.kernel.org" , "patrice.chotard@st.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 2019-05-01 at 16:25 +0200, Alexandre Belloni wrote: > On 30/04/2019 22:31:19+0000, Trent Piepho wrote: > > On Tue, 2019-04-30 at 22:18 +0200, Alexandre Belloni wrote: > > > The RTC core already ensures the alarm is set to a time in the future, it > > > is not necessary to check again in the driver. > > > > My reading of the rtc core code is that it checks if the alarm is in > > the future *twice* before handing off the set call to the driver, which > > possibly checks a 3rd time (as seen here). > > > > However, all these checks are done *before* setting the alarm. It > > still possible to have a race and set the alarm after the time has > > already passed, in which case the alarm will never fire. > > > > I agree the core need to handle that possible race better and this is > something I'm planning to work on. > > > The way to fix the race would be to have the driver check the alarm > > *after* setting it. In precisely this order, do these steps: > > > > 1. Set alarm in RTC, to Talarm > > 2. Get time from RTC, as Tcurrent > > 3. Get alarm status from RTC > > > > If Talarm < Tcurrent, alarm was set to future time, no error > > This should be Talarm > Tcurrent, right? Yes. I wrote that backward. > > Else > > If status == fired, alarm was set and has since fired, no error > > Else status == not fired, alarm was set in past, EINVAL > > > > This should be race free. > > > > > > > > > > - /* Invalid alarm time */ > > > - if (now_secs > alarm_secs) > > > - return -EINVAL; > > > - > > > memcpy(&rtc->alarm, t, sizeof(struct rtc_wkalrm)); > > > > > > /* Now many secs to fire */ > > > > alarm_secs -= now_secs; > > lpa = (unsigned long long)alarm_secs * rtc->clkrate; > > > > While it's true the time wouldn't normally be in past, it still races, > > as describe above. In that case, the math here underflows alarm_secs, > > so it probably still makes sense to check. > > I can't believe you can possibly have more than one second between the > check in the core and the check in the driver, it doesn't make much > sense to check, even in the current state of the core. It's certainly possible to have multiple seconds pass. For an external device over SPI or I2C, one has to wait for the bus to become free. And on SPI that requires the kernel thread running the bus to be scheduled. Just put in some real-time tasks and maybe a big transfer to a flash chip and it could be a while before that happens. I don't think this device has that issue as I don't think it's external. And ever for a device on an external bus, delays > 1 second are unlikely. Possible, but unlikely. You can also get them when Linux is running under a hypervisor, i.e. a Linux VM. But also something like an NMI and ACPI BIOS. If the Linux guest is not scheduled to run for while anything that is supposed to be based on real time, like the value returned by an RTC, will still advance. It is possible that multiple seconds elapse from the guest CPU executing one instruction to the next. But even ignoring that, does it require > 1 second to elapse. Can't it happen when the clock ticks from one second to the next, which happens effectively instantly? If the time from the check to the time when the alarm is set is 1 microsecond, and the time this call to set the alarm is made is randomly done and not synchronized to the RTC, then isn't there a 1 out of 1 million chance (1 microsecond / 1 second), that the once per second clock tick will hit our 1 us window? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel