From xen-devel-bounces@lists.xen.org Wed Nov 12 14:37:27 2014 Received: (at maildrop) by bugs.xenproject.org; 12 Nov 2014 14:37:27 +0000 Received: from lists.xen.org ([50.57.142.19]) by bugs.xenproject.org with esmtp (Exim 4.80) (envelope-from ) id 1XoZ31-0001mY-JA for xen-devel-maildrop-Eithu9ie@bugs.xenproject.org; Wed, 12 Nov 2014 14:37:27 +0000 Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XoYsg-0004mS-3c; Wed, 12 Nov 2014 14:26:46 +0000 Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XoYse-0004mL-IT for xen-devel@lists.xen.org; Wed, 12 Nov 2014 14:26:44 +0000 Received: from [85.158.143.35] by server-1.bemta-4.messagelabs.com id 48/B3-09842-32E63645; Wed, 12 Nov 2014 14:26:43 +0000 X-Env-Sender: julien.grall@linaro.org X-Msg-Ref: server-3.tower-21.messagelabs.com!1415802402!11872057!1 X-Originating-IP: [209.85.212.177] X-SpamReason: No, hits=0.0 required=7.0 tests= X-StarScan-Received: X-StarScan-Version: 6.12.4; banners=-,-,- X-VirusChecked: Checked Received: (qmail 20569 invoked from network); 12 Nov 2014 14:26:43 -0000 Received: from mail-wi0-f177.google.com (HELO mail-wi0-f177.google.com) (209.85.212.177) by server-3.tower-21.messagelabs.com with RC4-SHA encrypted SMTP; 12 Nov 2014 14:26:42 -0000 Received: by mail-wi0-f177.google.com with SMTP id l15so1143195wiw.10 for ; Wed, 12 Nov 2014 06:26:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type :content-transfer-encoding; bh=jkj4GO5zCAoEu8Qisewzv8UamF1H6RAGQTqcOHsoYT8=; b=PUkPfU6UnAeZC3suZRSy3SpjBehJzcpsPB9u/GTAuuJUq7d5b6k/ov40dnLKpyA1tK dZqAOk1l1TyrpPyn9LfLHTJrbxGDMdCUusu2MIMM7cSfEWWwWUK5A1IrEeFJA/PY1ODc jZf0HKUJJ6Gk8OCvz84QRBBER02qFuwG75bdTleV86WpofAlmKtmNftN9o0dj/TvqVb3 nwKM8xjDY/ncLF48ZwF/jZzBYvI2kmdZNW5aPoG+SE6GNtN3tJYVHCPfcyER0b2bFfQX ByFif2jmWPPz6OdxmAA+vKqm03RQBeBEIjG6EoPuZXC8wduw9DL6GOGdMwIrZ5hBvXb0 v21Q== X-Gm-Message-State: ALoCoQmLXUTqfi83jVtG+ZxdQbNwnNmVbM0G4SMLWD8pTFPT6DFCsrn2LfL6YYXOkBSRNqaYgnzv X-Received: by 10.194.184.199 with SMTP id ew7mr44027741wjc.85.1415802402722; Wed, 12 Nov 2014 06:26:42 -0800 (PST) Received: from [10.80.2.139] ([185.25.64.249]) by mx.google.com with ESMTPSA id lp14sm19903375wic.20.2014.11.12.06.26.41 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 12 Nov 2014 06:26:41 -0800 (PST) Message-ID: <54636E1A.50504@linaro.org> Date: Wed, 12 Nov 2014 14:26:34 +0000 From: Julien Grall User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Icedove/24.8.1 MIME-Version: 1.0 To: Ian Campbell References: <1414579268.29975.13.camel@citrix.com> <1414579302-6692-18-git-send-email-ian.campbell@citrix.com> <21585.6188.366311.80971@mariner.uk.xensource.com> <1414672390.2064.31.camel@citrix.com> <54623E3D.4060803@linaro.org> <1415786876.25176.49.camel@citrix.com> In-Reply-To: <1415786876.25176.49.camel@citrix.com> Cc: xen-devel@lists.xen.org, Ian Jackson , Stefano Stabellini Subject: Re: [Xen-devel] [PATCH OSSTEST v2 18/20] Osstest/Debian: Add "clk_ignore_unused" to default command line X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org On 11/12/2014 10:07 AM, Ian Campbell wrote: > On Tue, 2014-11-11 at 17:50 +0100, Julien Grall wrote: >> Hi, >> >> Somehow I missed this email. >> >> On 30/10/2014 13:33, Ian Campbell wrote: >>> create ! >>> title it arm: domain 0 disables clocks which are in fact being used >>> thanks >>> >>> On Wed, 2014-10-29 at 16:39 +0000, Ian Jackson wrote: >>>> Ian Campbell writes ("[PATCH OSSTEST v2 18/20] Osstest/Debian: Add "clk_ignore_unused" to default command line"): >>>>> This stops dom0 from messing with clocks which it should and is required on >>>>> some platforms. It's harmless even when not needed. >>>> >>>> This is pretty odd. Doesn't this correspond to some kind of bug, in >>>> the dom0 kernel perhaps ? >>> >>> dom0 is not aware that some clocks are actually in use (e.g. by the >>> hypervisor), so the bug is probably in the lack of some interface to >>> communicate this from Xen to dom0, or some other mechanism to gate this. >> >> In reality, Xen is only using the clock of the UART. Even though, I >> think this would also happen with platform device passthrough. >> >> For the latter, it would be fairly easy via a PV drivers. But for >> UART... gating the clock could be a nightmare because every platform >> have their own way to enable/disable the clock. Futhermore, the clock >> could be shared with multiple device... >> >> I'm wondering if we could expose the UART to DOM0 without marking as >> disabled. It would avoid DOM0 to mess up the clock while everything >> would be catch via the vuart implementation in Xen. > > Perhaps we could propagate any clock related properties from the UART > node into the Xen hypervisor node (or a subnode)? The Xen Linux code > would then consume those and mark the relevant clocks as in use. I've > not looked into the clock bindings to know how plausible this might be. It looks like the bindings for clock is well defined and fairly common (Documentation/devicetree/bindins/clock/clock-bindings.txt). So your solution sounds plausible. Regards, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel