From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1517306513; cv=none; d=google.com; s=arc-20160816; b=vDpyCfjA5RD1ZuP39HoUh2roXzBDUB76dytIq0WMIPi0nMwyWQUvqDxnOIxeJOUPPe ie7/6ZxCMMUmyzM4x06I66ztVDZU9y2b+lB2g6+R4ovhzwHeKO8wc3h9sUPMP2e3+oO7 W4KdPA/70EARs/E49OA6HBnKS3c8gPTuV7j6kUG+eLTl8wH4AmAPqy1Ps1HkAa5DOXWr BrrTxLasFU7in12Ov8x1AEJ9h8jmitwlKjeCi2G1VWIQNsReWawaHzPGYkUw9W651Prn K1MM9nXjayugTQ51adhD3ndhDUvoWdQUZMGSPfE6P6k6b3H4gbFXo/nTpc2ikaqDCUqU 7vdg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature :arc-authentication-results; bh=w0TD/m+LGnDzeJeumEK1zcDkq5TYPPFqfAsRadsCIWo=; b=bJsuFlEFmvk7ZwwW3LjUx1FnVDIP3kHO2MYTbZ7kDth4vKS//bEdHkyEF4JB9j3ZWV 4gkf97cA2ZWlmIKkeW1bf2aBn5+bAw/vCSoTxP0tDwDCPLQcWgT59ciOuq2MPL8OA/+c OEGkFXn+uXWWaNG++6U7s4SN+sKP/ZmHJbhiPe45O+W7WjrzAOUAelimrUk16BCGvZsA moSA1CFV1A+c62z7og/186k6haROZxhXP1/tL2Yk0K10Ik6g2PJytCvCyV2uaklU72pF hlIhBx1vjEfksRMgWSvJ/y3VC071B0CYjAldGzq3pNBZuzZ0qlU99vGK9B4ie2J8cIpb tYzA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=J/IHGfwm; spf=pass (google.com: domain of thierry.reding@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=thierry.reding@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=J/IHGfwm; spf=pass (google.com: domain of thierry.reding@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=thierry.reding@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com X-Google-Smtp-Source: AH8x224a14lzXeUWf2Om2fvQUeujahvflI4XZWSY8eaMcO/OfxYjCrzkL2BN9MD7o6SfRFcRDMcklA== Date: Tue, 30 Jan 2018 11:01:50 +0100 From: Thierry Reding To: Arnd Bergmann Cc: Dave Martin , Maxime Ripard , Linus Walleij , Yong Deng , Mauro Carvalho Chehab , Rob Herring , Mark Rutland , Chen-Yu Tsai , "David S. Miller" , Greg Kroah-Hartman , Hans Verkuil , Randy Dunlap , Stanimir Varbanov , Hugues Fruchet , Yannick Fertre , Philipp Zabel , Benjamin Gaignard , Ramesh Shanmugasundaram , Sakari Ailus , Rick Chang , Linux Media Mailing List , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Linux ARM , "linux-kernel@vger.kernel.org" , linux-sunxi , megous@megous.com, Thomas Petazzoni Subject: Re: [PATCH v6 2/2] media: V3s: Add support for Allwinner CSI. Message-ID: <20180130100150.GB23047@ulmo> References: <1516695531-23349-1-git-send-email-yong.deng@magewell.com> <20180129082533.6edmqgbauo6q5dgz@flea.lan> <20180130075441.rqxzkwero6sdfak6@flea.lan> <20180130095916.GA23047@ulmo> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="GID0FwUMdk1T2AWN" Content-Disposition: inline In-Reply-To: <20180130095916.GA23047@ulmo> User-Agent: Mutt/1.9.1 (2017-09-22) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590370608168306586?= X-GMAIL-MSGID: =?utf-8?q?1591011194420724498?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: --GID0FwUMdk1T2AWN Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jan 30, 2018 at 10:59:16AM +0100, Thierry Reding wrote: > On Tue, Jan 30, 2018 at 10:24:48AM +0100, Arnd Bergmann wrote: > > On Tue, Jan 30, 2018 at 8:54 AM, Maxime Ripard > > wrote: > > > On Mon, Jan 29, 2018 at 03:34:02PM +0100, Arnd Bergmann wrote: > > >> On Mon, Jan 29, 2018 at 10:25 AM, Linus Walleij > > >> wrote: > > >> > On Mon, Jan 29, 2018 at 9:25 AM, Maxime Ripard > > >> > wrote: > > >> >> On Sat, Jan 27, 2018 at 05:14:26PM +0100, Linus Walleij wrote: > >=20 > > >> > > >> At one point we had discussed adding a 'dma-masters' property that > > >> lists all the buses on which a device can be a dma master, and > > >> the respective properties of those masters (iommu, coherency, > > >> offset, ...). > > >> > > >> IIRC at the time we decided that we could live without that complexi= ty, > > >> but perhaps we cannot. > > > > > > Are you talking about this ? > > > https://elixir.free-electrons.com/linux/latest/source/Documentation/d= evicetree/bindings/dma/dma.txt#L41 > > > > > > It doesn't seem to be related to that issue to me. And in our > > > particular cases, all the devices are DMA masters, the RAM is just > > > mapped to another address. > >=20 > > No, that's not the one I was thinking of. The idea at the time was much > > more generic, and not limited to dma engines. I don't recall the detail= s, > > but I think that Thierry was either involved or made the proposal at the > > time. >=20 > Yeah, I vaguely remember discussing something like this before. A quick > search through my inbox yielded these two threads, mostly related to > IOMMU but I think there were some mentions about dma-ranges and so on as > well. I'll have to dig deeper into those threads to refresh my memories, > but I won't get around to it until later today. >=20 > If someone wants to read up on this in the meantime, here are the links: >=20 > https://lkml.org/lkml/2014/4/27/346 > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/257200.ht= ml >=20 > From a quick glance the issue of dma-ranges was something that we hand- > waved at the time. >=20 > Thierry Also found this, which seems to be relevant as well: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/252715.html Adding Dave. 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