From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1622860-1516273700-2-6600599613313015092 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, FREEMAIL_FORGED_FROMDOMAIN 0.25, FREEMAIL_FROM 0.001, HEADER_FROM_DIFFERENT_DOMAINS 0.25, RCVD_IN_DNSWL_NONE -0.0001, RCVD_IN_MSPIKE_H3 -0.01, RCVD_IN_MSPIKE_WL -0.01, SPF_PASS -0.001, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.85.218.65', Host='mail-oi0-f65.google.com', Country='US', FromHeader='de', MailFrom='com' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: arndbergmann@gmail.com ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1516273700; b=moawVn5T9ntngFUMx44JXWmhLHCp89/otE9I8UdK1NiWdVs ovWXbs3sCvDV6MQiifg7ijTjA5hFn2ms9nzwE95OGZk2o/T6zvOn/IzmoUKARIei Ux8m4ul1RMauYbMnMkEAOvD2Xk3cW621CKplr8Gq6vwgejt61BpwxV/sfWghfN8L wBmH9wqIzDw0Kew+NHfLbKuT1eAe2oSBmcg9N9v4+HgQaaf5JfVnETB+Ml654Bsb x8L6y0wjsTlIqnE6Hzeh67o8TZN9mRzFF9BTFcqEKRQVGamrsbRhchj/L+x7bfdx JC4d7kof1WZ/o61/5mxznyYyVv0gceuIiyngBPg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=mime-version:sender:in-reply-to :references:from:date:message-id:subject:to:cc:content-type; s= arctest; t=1516273700; bh=qduMPJPEM4NME/ZTDXUwYgkOiULq2EDbsSGIon /laQM=; b=N/Kmv7NKleaNZ3qLVeT4fbi1J19ObN3pTcfk9A/fff516kbXeF8P62 0nGyYmM6MMLOa6CnEsgv/Z072FotyjjRCEYgHVltqd+r6t2K2/AH//hMKYPNXUVp m43FgEySjJ1G043/cLxnsOUwZf9ewwBcQMy556WEHRplgIMD+I6df2y8G0BsjZlg ZuixTj3GcoYez9QcW40R9gqEE55Mwz0d6MYh5uFbwb8ms8oAklqhM1pe91mzxaMt Ev+gxuJ+bNvCcvE2PXWIgQCBLfOyBjIKPDanUvkWgmxzP2ln6WPY7gQNb4r1ZhBC G/z39/9CP4zSDuDZV/FZa8f0wxdqYxCQ== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=Habcm9s7 x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=arndb.de; iprev=pass policy.iprev=209.85.218.65 (mail-oi0-f65.google.com); spf=pass smtp.mailfrom=arndbergmann@gmail.com smtp.helo=mail-oi0-f65.google.com; x-aligned-from=fail; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=HiCJ6koP; x-ptr=pass x-ptr-helo=mail-oi0-f65.google.com x-ptr-lookup=mail-oi0-f65.google.com; x-return-mx=pass smtp.domain=gmail.com smtp.result=pass smtp_is_org_domain=yes header.domain=arndb.de header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=Habcm9s7 x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=arndb.de; iprev=pass policy.iprev=209.85.218.65 (mail-oi0-f65.google.com); spf=pass smtp.mailfrom=arndbergmann@gmail.com smtp.helo=mail-oi0-f65.google.com; x-aligned-from=fail; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=HiCJ6koP; x-ptr=pass x-ptr-helo=mail-oi0-f65.google.com x-ptr-lookup=mail-oi0-f65.google.com; x-return-mx=pass smtp.domain=gmail.com smtp.result=pass smtp_is_org_domain=yes header.domain=arndb.de header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Google-Smtp-Source: ACJfBosP+HFLjRd7zN2FaBrf+ZaWZWrMFaMLqlzxmMlzuquTFSft0srrGqTQrbg0PCmKnzsWH9s0QadImyA2LbQqFAE= MIME-Version: 1.0 Sender: arndbergmann@gmail.com In-Reply-To: References: From: Arnd Bergmann Date: Thu, 18 Jan 2018 12:08:17 +0100 X-Google-Sender-Auth: 3PbBZqrtS4HptuGhqO4TG0IE4bU Message-ID: Subject: Re: [PATCH v6 2/3] clocksource/drivers/atcpit100: VDSO support To: Greentime Hu Cc: Greentime , Linux Kernel Mailing List , linux-arch , Thomas Gleixner , Jason Cooper , Marc Zyngier , Rob Herring , Networking , Vincent Chen , DTML , Al Viro , David Howells , Will Deacon , Daniel Lezcano , linux-serial@vger.kernel.org, Geert Uytterhoeven , Linus Walleij , Mark Rutland , Greg KH , Guo Ren , Randy Dunlap , David Miller , Jonas Bonn , Stefan Kristiansson , Stafford Horne , Rick Chen , Rick Chen , Vincent Chen Content-Type: text/plain; charset="UTF-8" X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, Jan 15, 2018 at 6:57 AM, Greentime Hu wrote: > From: Rick Chen > > VDSO needs real-time cycle count to ensure the time accuracy. > Unlike others, nds32 architecture does not define clock source, > hence VDSO needs atcpit100 offering real-time cycle count > to derive the correct time. > > Signed-off-by: Vincent Chen > Signed-off-by: Rick Chen > Signed-off-by: Greentime Hu I'm a bit puzzled by this patch, can you explain how the vdso actually manages to access the clock hardware? It looks like you make the physical address and the register offset available to user space, but how does it end up accessing it? Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v6 2/3] clocksource/drivers/atcpit100: VDSO support Date: Thu, 18 Jan 2018 12:08:17 +0100 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Greentime , Linux Kernel Mailing List , linux-arch , Thomas Gleixner , Jason Cooper , Marc Zyngier , Rob Herring , Networking , Vincent Chen , DTML , Al Viro , David Howells , Will Deacon , Daniel Lezcano , linux-serial@vger.kernel.org, Geert Uytterhoeven , Linus Walleij , Mark Rutland , Greg KH , Guo Ren Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Jan 15, 2018 at 6:57 AM, Greentime Hu wrote: > From: Rick Chen > > VDSO needs real-time cycle count to ensure the time accuracy. > Unlike others, nds32 architecture does not define clock source, > hence VDSO needs atcpit100 offering real-time cycle count > to derive the correct time. > > Signed-off-by: Vincent Chen > Signed-off-by: Rick Chen > Signed-off-by: Greentime Hu I'm a bit puzzled by this patch, can you explain how the vdso actually manages to access the clock hardware? It looks like you make the physical address and the register offset available to user space, but how does it end up accessing it? Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v6 2/3] clocksource/drivers/atcpit100: VDSO support Date: Thu, 18 Jan 2018 12:08:17 +0100 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Greentime Hu Cc: Greentime , Linux Kernel Mailing List , linux-arch , Thomas Gleixner , Jason Cooper , Marc Zyngier , Rob Herring , Networking , Vincent Chen , DTML , Al Viro , David Howells , Will Deacon , Daniel Lezcano , linux-serial@vger.kernel.org, Geert Uytterhoeven , Linus Walleij , Mark Rutland , Greg KH , Guo Ren List-Id: devicetree@vger.kernel.org On Mon, Jan 15, 2018 at 6:57 AM, Greentime Hu wrote: > From: Rick Chen > > VDSO needs real-time cycle count to ensure the time accuracy. > Unlike others, nds32 architecture does not define clock source, > hence VDSO needs atcpit100 offering real-time cycle count > to derive the correct time. > > Signed-off-by: Vincent Chen > Signed-off-by: Rick Chen > Signed-off-by: Greentime Hu I'm a bit puzzled by this patch, can you explain how the vdso actually manages to access the clock hardware? It looks like you make the physical address and the register offset available to user space, but how does it end up accessing it? Arnd