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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 710A6C433F5 for ; Thu, 17 Mar 2022 11:11:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=b4Jf2dKo2VRuX/zTuqXQ9q7FIhevJsB6amkNI6uqWLk=; b=Z5ZnG4EjDeDLT7 idL/3DmkjpTR0zxvdFhQ+et3K2x7b2UKDnqchReme+Q+fvR8Oy16b6Plud8rG395ATOeNLFx1Aohj fuy/c27WTxkWSRjAJU18EEdbbyXyiRO2GbjJ/wisB39uLMVVSpwLiPDSLUiWhE/y6NCr998+YfyTm xlKJqDW4ivN2ZYF7xqRHxO7UllFgnTr1eb7Xhs0izaC4X717nTxxMReaywx1rlGy7eOMUlBSQUkL1 JjKtgiQENocIfhNFjHFEppO2QtxSwlUrWasp2Mgsnx4Jb6GIde1R0I6sQlLqB/TdAeUQgnzzrwtht QTv9tPtiyzz0rXbXAWKw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nUo1V-00Fmn3-2e; Thu, 17 Mar 2022 11:10:29 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nUo1S-00Fmlk-CU for linux-mtd@lists.infradead.org; Thu, 17 Mar 2022 11:10:28 +0000 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-255-MiCiRbVUN16QRgYdqh5Xig-1; Thu, 17 Mar 2022 11:10:22 +0000 X-MC-Unique: MiCiRbVUN16QRgYdqh5Xig-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Thu, 17 Mar 2022 11:10:21 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.033; Thu, 17 Mar 2022 11:10:21 +0000 From: David Laight To: 'Vignesh Raghavendra' , 'Michael Walle' CC: Tudor Ambarus , "p.yadav@ti.com" , "broonie@kernel.org" , "miquel.raynal@bootlin.com" , "richard@nod.at" , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-spi@vger.kernel.org" , "nicolas.ferre@microchip.com" Subject: RE: [PATCH v2 0/6] spi-mem: Allow specifying the byte order in DTR mode Thread-Topic: [PATCH v2 0/6] spi-mem: Allow specifying the byte order in DTR mode Thread-Index: AQHYOQSPIX1seC7nAUuKrYcK6uPoWazCAVMggAFSn4CAAATp8IAABzYAgAAFzgA= Date: Thu, 17 Mar 2022 11:10:21 +0000 Message-ID: References: <20220311080147.453483-1-tudor.ambarus@microchip.com> <76eb13b6-9263-975f-3196-312259634301@ti.com> <0f271365-354b-82e2-02a2-9d69a6ac85b1@ti.com> <9bc530d1fdaf4490a00fee150f963ac7@AcuMS.aculab.com> <8b765d24cb9a422bb383aad07251b65f@AcuMS.aculab.com> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220317_041026_719788_B3D615E7 X-CRM114-Status: GOOD ( 10.25 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org From: Vignesh Raghavendra > Sent: 17 March 2022 10:24 ... > Modern OSPI/QSPI flash controllers provide MMIO interface to read from > flash where DMA can pull data as if though you are reading from On chip RAM So the cpu does an MMIO read cycle to the controller which doesn't complete until (for the nibble-mode spi device I have): 1) Chipselect is asserted. 2) The 8-bit command has been clocked out. 3) The 32bit address have been clocked out (8 clocks in nibbles). 4) A few (probably 4) extra delay clocks are added. 5) The data is read - 8 clocks for 32bits in nibble mode. 6) Chipselect is removed. Now you can do long sequential reads without all the red tape. But a random read in nibble mode is about 30 clocks. 16 bit mode saves 6 clocks for the data and maybe 6 for the address? The controller could do 'clever stuff' for sequential reads. At a cost of slowing down random reads. So even at 400MHz it isn't that fast. If the MMIO interface to the flash controller is PCIe you can add in a load of extra latency for the cpu read itself. While PCIe allows multiple read requests to be outstanding, the Intel cpu I've looked at serialise the reads from each cpu core (each cpu always uses the same TLP tag). Now longer read TLP help a lot (IIRC max is 256 bytes). But the x86 cpu will only generate read TLP for register reads. You need to use AVX512 registers (or cache line fetches) to get better throughput! The alternative is getting the flash controller to issue the read/write TLP for memory transfers. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/ 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE914C433EF for ; Thu, 17 Mar 2022 11:10:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232865AbiCQLLo (ORCPT ); Thu, 17 Mar 2022 07:11:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52498 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232640AbiCQLLn (ORCPT ); Thu, 17 Mar 2022 07:11:43 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B27881DBA89 for ; Thu, 17 Mar 2022 04:10:25 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-255-MiCiRbVUN16QRgYdqh5Xig-1; Thu, 17 Mar 2022 11:10:22 +0000 X-MC-Unique: MiCiRbVUN16QRgYdqh5Xig-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Thu, 17 Mar 2022 11:10:21 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.033; Thu, 17 Mar 2022 11:10:21 +0000 From: David Laight To: 'Vignesh Raghavendra' , 'Michael Walle' CC: Tudor Ambarus , "p.yadav@ti.com" , "broonie@kernel.org" , "miquel.raynal@bootlin.com" , "richard@nod.at" , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-spi@vger.kernel.org" , "nicolas.ferre@microchip.com" Subject: RE: [PATCH v2 0/6] spi-mem: Allow specifying the byte order in DTR mode Thread-Topic: [PATCH v2 0/6] spi-mem: Allow specifying the byte order in DTR mode Thread-Index: AQHYOQSPIX1seC7nAUuKrYcK6uPoWazCAVMggAFSn4CAAATp8IAABzYAgAAFzgA= Date: Thu, 17 Mar 2022 11:10:21 +0000 Message-ID: References: <20220311080147.453483-1-tudor.ambarus@microchip.com> <76eb13b6-9263-975f-3196-312259634301@ti.com> <0f271365-354b-82e2-02a2-9d69a6ac85b1@ti.com> <9bc530d1fdaf4490a00fee150f963ac7@AcuMS.aculab.com> <8b765d24cb9a422bb383aad07251b65f@AcuMS.aculab.com> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: base64 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org RnJvbTogVmlnbmVzaCBSYWdoYXZlbmRyYQ0KPiBTZW50OiAxNyBNYXJjaCAyMDIyIDEwOjI0DQou Li4NCj4gTW9kZXJuIE9TUEkvUVNQSSBmbGFzaCBjb250cm9sbGVycyBwcm92aWRlIE1NSU8gaW50 ZXJmYWNlIHRvIHJlYWQgZnJvbQ0KPiBmbGFzaCB3aGVyZSBETUEgY2FuIHB1bGwgZGF0YSBhcyBp ZiB0aG91Z2ggeW91IGFyZSByZWFkaW5nIGZyb20gT24gY2hpcCBSQU0NCg0KU28gdGhlIGNwdSBk b2VzIGFuIE1NSU8gcmVhZCBjeWNsZSB0byB0aGUgY29udHJvbGxlciB3aGljaCBkb2Vzbid0DQpj b21wbGV0ZSB1bnRpbCAoZm9yIHRoZSBuaWJibGUtbW9kZSBzcGkgZGV2aWNlIEkgaGF2ZSk6DQox KSBDaGlwc2VsZWN0IGlzIGFzc2VydGVkLg0KMikgVGhlIDgtYml0IGNvbW1hbmQgaGFzIGJlZW4g Y2xvY2tlZCBvdXQuDQozKSBUaGUgMzJiaXQgYWRkcmVzcyBoYXZlIGJlZW4gY2xvY2tlZCBvdXQg KDggY2xvY2tzIGluIG5pYmJsZXMpLg0KNCkgQSBmZXcgKHByb2JhYmx5IDQpIGV4dHJhIGRlbGF5 IGNsb2NrcyBhcmUgYWRkZWQuDQo1KSBUaGUgZGF0YSBpcyByZWFkIC0gOCBjbG9ja3MgZm9yIDMy Yml0cyBpbiBuaWJibGUgbW9kZS4NCjYpIENoaXBzZWxlY3QgaXMgcmVtb3ZlZC4NCg0KTm93IHlv dSBjYW4gZG8gbG9uZyBzZXF1ZW50aWFsIHJlYWRzIHdpdGhvdXQgYWxsIHRoZSByZWQgdGFwZS4N CkJ1dCBhIHJhbmRvbSByZWFkIGluIG5pYmJsZSBtb2RlIGlzIGFib3V0IDMwIGNsb2Nrcy4NCjE2 IGJpdCBtb2RlIHNhdmVzIDYgY2xvY2tzIGZvciB0aGUgZGF0YSBhbmQgbWF5YmUgNiBmb3IgdGhl IGFkZHJlc3M/DQoNClRoZSBjb250cm9sbGVyIGNvdWxkIGRvICdjbGV2ZXIgc3R1ZmYnIGZvciBz ZXF1ZW50aWFsIHJlYWRzLg0KQXQgYSBjb3N0IG9mIHNsb3dpbmcgZG93biByYW5kb20gcmVhZHMu DQoNClNvIGV2ZW4gYXQgNDAwTUh6IGl0IGlzbid0IHRoYXQgZmFzdC4NCg0KSWYgdGhlIE1NSU8g aW50ZXJmYWNlIHRvIHRoZSBmbGFzaCBjb250cm9sbGVyIGlzIFBDSWUgeW91IGNhbg0KYWRkIGlu IGEgbG9hZCBvZiBleHRyYSBsYXRlbmN5IGZvciB0aGUgY3B1IHJlYWQgaXRzZWxmLg0KDQpXaGls ZSBQQ0llIGFsbG93cyBtdWx0aXBsZSByZWFkIHJlcXVlc3RzIHRvIGJlIG91dHN0YW5kaW5nLA0K dGhlIEludGVsIGNwdSBJJ3ZlIGxvb2tlZCBhdCBzZXJpYWxpc2UgdGhlIHJlYWRzIGZyb20gZWFj aA0KY3B1IGNvcmUgKGVhY2ggY3B1IGFsd2F5cyB1c2VzIHRoZSBzYW1lIFRMUCB0YWcpLg0KDQpO b3cgbG9uZ2VyIHJlYWQgVExQIGhlbHAgYSBsb3QgKElJUkMgbWF4IGlzIDI1NiBieXRlcykuDQpC dXQgdGhlIHg4NiBjcHUgd2lsbCBvbmx5IGdlbmVyYXRlIHJlYWQgVExQIGZvciByZWdpc3RlciBy ZWFkcy4NCllvdSBuZWVkIHRvIHVzZSBBVlg1MTIgcmVnaXN0ZXJzIChvciBjYWNoZSBsaW5lIGZl dGNoZXMpIHRvDQpnZXQgYmV0dGVyIHRocm91Z2hwdXQhDQoNClRoZSBhbHRlcm5hdGl2ZSBpcyBn ZXR0aW5nIHRoZSBmbGFzaCBjb250cm9sbGVyIHRvIGlzc3VlDQp0aGUgcmVhZC93cml0ZSBUTFAg Zm9yIG1lbW9yeSB0cmFuc2ZlcnMuDQoNCglEYXZpZA0KDQotDQpSZWdpc3RlcmVkIEFkZHJlc3Mg TGFrZXNpZGUsIEJyYW1sZXkgUm9hZCwgTW91bnQgRmFybSwgTWlsdG9uIEtleW5lcywgTUsxIDFQ VCwgVUsNClJlZ2lzdHJhdGlvbiBObzogMTM5NzM4NiAoV2FsZXMpDQo=