From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH v3 1/7] dt-bindings: interconnect: Add a dma interconnect name Date: Mon, 11 Mar 2019 11:11:30 +0100 Message-ID: <20190311101130.7t7rctxlqly3uqmt@flea> References: <43eeca13733faefe62f9facc25b8e88f7e593f61.1549897336.git-series.maxime.ripard@bootlin.com> <553c987c-da9a-1f85-fb16-4b9fe17dd14b@linaro.org> <20190305155337.glfvgyddvnkv774m@flea> <0e72fbf7-b100-ddc5-3c19-32f71c37f76f@arm.com> <477995b0-9ac3-b6ca-f5f2-856e4af926f1@linaro.org> <20190307154755.5kgc7oh4b5bhg2fj@flea> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1993862453==" Return-path: Received: from relay8-d.mail.gandi.net (relay8-d.mail.gandi.net [217.70.183.201]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8AC7F89993 for ; Mon, 11 Mar 2019 10:11:36 +0000 (UTC) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Chen-Yu Tsai Cc: Mark Rutland , devicetree , Thomas Petazzoni , Arnd Bergmann , Robin Murphy , dri-devel , Dave Martin , Paul Kocialkowski , Chen-Yu Tsai , Rob Herring , Yong Deng , Frank Rowand , Georgi Djakov , linux-arm-kernel List-Id: dri-devel@lists.freedesktop.org --===============1993862453== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="cgjcr5o5hj4pdzgw" Content-Disposition: inline --cgjcr5o5hj4pdzgw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 08, 2019 at 12:09:47AM +0800, Chen-Yu Tsai wrote: > On Thu, Mar 7, 2019 at 11:48 PM Maxime Ripard = wrote: > > > > On Thu, Mar 07, 2019 at 05:15:20PM +0200, Georgi Djakov wrote: > > > Hi, > > > > > > On 3/5/19 18:14, Robin Murphy wrote: > > > > On 05/03/2019 15:53, Maxime Ripard wrote: > > > >> Hi, > > > >> > > > >> On Fri, Mar 01, 2019 at 07:48:15PM +0200, Georgi Djakov wrote: > > > >>> On 2/11/19 17:02, Maxime Ripard wrote: > > > >>>> The current DT bindings assume that the DMA will be performed by= the > > > >>>> devices through their parent DT node, and rely on that assumption > > > >>>> for the > > > >>>> address translation using dma-ranges. > > > >>>> > > > >>>> However, some SoCs have devices that will perform DMA through > > > >>>> another bus, > > > >>>> with separate address translation rules. We therefore need to > > > >>>> express that > > > >>>> relationship, through the special interconnect name "dma". > > > >>>> > > > >>>> Signed-off-by: Maxime Ripard > > > >>>> --- > > > >>>> Documentation/devicetree/bindings/interconnect/interconnect.tx= t | > > > >>>> 3 +++ > > > >>>> 1 file changed, 3 insertions(+) > > > >>>> > > > >>>> diff --git > > > >>>> a/Documentation/devicetree/bindings/interconnect/interconnect.txt > > > >>>> b/Documentation/devicetree/bindings/interconnect/interconnect.txt > > > >>>> index 5a3c575b387a..e69fc2d992c3 100644 > > > >>>> --- a/Documentation/devicetree/bindings/interconnect/interconnec= t.txt > > > >>>> +++ b/Documentation/devicetree/bindings/interconnect/interconnec= t.txt > > > >>>> @@ -51,6 +51,9 @@ interconnect-names : List of interconnect path > > > >>>> name strings sorted in the same > > > >>>> interconnect-names to match interconnect paths wi= th > > > >>>> interconnect > > > >>>> specifier pairs. > > > >>>> + Reserved interconnect names: > > > >>>> + * dma: Path from the device to the main > > > >>>> memory of the system > > > >>> > > > >>> Bikeshed: As it's from the device to the main memory, maybe here = we can > > > >>> also denote this my calling the path dma-mem or dma-memory. For o= ther > > > >>> paths, we are trying to mention both the source and the destinati= on and > > > >>> maybe it would be good to be consistent although this is special = one. > > > >> > > > >> I'm not sure I understand what you mean. You'd like two interconne= ct > > > >> names, one called dma-memory, and one memory-dma? > > > > > > > > Hmm, yes, it's not like "dma" describes an actual source or destina= tion > > > > either :/ > > > > > > IIUC, it's a path (bus) that a dma device use to access some memory > > > (read or/and write). So i have used source-destination above more in = the > > > sense of initiator-target or master-slave. My suggestion was just to > > > change the reserved interconnect name from "dma" to "dma-mem" or > > > "dma-memory". > > > > If dma is an issue in itself, maybe we can call it "device-memory" ? >=20 > Might I ask what happens if the device can both DMA to and from memory? We can create another one called memory-device if that's needed? > IIRC the display frontends, backends, and mixers all have writeback > capability, using the same interconnect port. I think in both cases it's the same path. The camera driver also need to have that offset, even though it's a producer and not a consumer, and the VPU does too. Maxime --=20 Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --cgjcr5o5hj4pdzgw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXIY0UgAKCRDj7w1vZxhR xWlzAQDQWxjEX8QrpJ0nCrdPzyE5N6pgFtbmWODK1evHzMqRTQEA8b3Igx1mPZoF I5Smn7hZCFuJtSJuAFxmmpEUIMVwtgQ= =UI++ -----END PGP SIGNATURE----- --cgjcr5o5hj4pdzgw-- --===============1993862453== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVs IG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8vbGlz dHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVs --===============1993862453==--