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Date: Tue, 21 Aug 2018 12:43:52 +0200 From: Boris Brezillon <boris.brezillon@...tlin.com> To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org> Cc: Alban <albeu@...e.fr>, Bartosz Golaszewski <brgl@...ev.pl>, Jonathan Corbet <corbet@....net>, Sekhar Nori <nsekhar@...com>, Kevin Hilman <khilman@...nel.org>, Russell King <linux@...linux.org.uk>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, David Woodhouse <dwmw2@...radead.org>, Brian Norris <computersforpeace@...il.com>, Marek Vasut <marek.vasut@...il.com>, Richard Weinberger <richard@....at>, Grygorii Strashko <grygorii.strashko@...com>, "David S . Miller" <davem@...emloft.net>, Naren <naren.kernel@...il.com>, Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Lukas Wunner <lukas@...ner.de>, Dan Carpenter <dan.carpenter@...cle.com>, Florian Fainelli <f.fainelli@...il.com>, Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>, Sven Van Asbroeck <svendev@...x.com>, Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>, David Lechner <david@...hnology.com>, Andrew Lunn <andrew@...n.ch>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org, linux-mtd@...ts.infradead.org, linux-omap@...r.kernel.org, netdev@...r.kernel.org, Bartosz Golaszewski <bgolaszewski@...libre.com> Subject: Re: [PATCH v2 06/29] mtd: Add support for reading MTD devices via the nvmem API On Tue, 21 Aug 2018 11:11:58 +0100 Srinivas Kandagatla <srinivas.kandagatla@...aro.org> wrote: > On 21/08/18 10:56, Boris Brezillon wrote: > > On Tue, 21 Aug 2018 10:50:07 +0100 > > Srinivas Kandagatla<srinivas.kandagatla@...aro.org> wrote: > > > >> On 20/08/18 19:20, Boris Brezillon wrote: > >>> On Mon, 20 Aug 2018 11:43:34 +0100 > >>> Srinivas Kandagatla<srinivas.kandagatla@...aro.org> wrote: > >>> > >>>> Overall am still not able to clear visualize on how MTD bindings with > >>>> nvmem cells would look in both partition and un-partition usecases? > >>>> An example DT would be nice here!! > >>> Something along those lines: > >>> > >> This looks good to me. > >>> mtdnode { > >>> nvmem-cells { > >>> #address-cells = <1>; > >>> #size-cells = <1>; > >>> > >>> cell@0 { > >>> reg = <0x0 0x14>; > >>> }; > >>> }; > >>> > >>> partitions { > >>> compatible = "fixed-partitions"; > >>> #address-cells = <1>; > >>> #size-cells = <1>; > >>> > >>> partition@0 { > >>> reg = <0x0 0x20000>; > >>> > >>> nvmem-cells { > >>> #address-cells = <1>; > >>> #size-cells = <1>; > >>> > >>> cell@0 { > >>> reg = <0x0 0x10>; > >>> }; > >>> }; > >>> }; > >>> }; > >>> }; > > >> Just curious...Is there a reason why we can't do it like this?: > >> Is this because of issue of #address-cells and #size-cells Or mtd > >> bindings always prefer subnodes? > >> > >> mtdnode { > >> reg = <0x0123000 0x40000>; > >> #address-cells = <1>; > >> #size-cells = <1>; > >> cell@0 { > >> compatible = "nvmem-cell"; > >> reg = <0x0 0x14>; > >> }; > >> > >> partitions { > >> compatible = "fixed-partitions"; > >> #address-cells = <1>; > >> #size-cells = <1>; > >> > >> partition@0 { > >> reg = <0x0 0x20000>; > >> cell@0 { > >> compatible = "nvmem-cell"; > >> reg = <0x0 0x10>; > >> }; > >> }; > >> }; > >> }; > > It's because partitions were initially directly defined under the mtd > > node, so, if you have an old DT you might have something like: > > > > mtdnode { > > reg = <0x0123000 0x40000>; > > #address-cells = <1>; > > #size-cells = <1>; > > > > partition@0 { > > reg = <0x0 0x20000>; > > ... > > }; > > ... > > }; > > > > If we use such a DT with this patch applied, the NVMEM framework will > > consider MTD partitions as nvmem cells, which is not what we want. > Yep, I agree. > TBH, I wanted to add compatible string to nvmem-cell at some point in > time and it seems more natural update too. One of the reason we > discussed this in the past was parsers. Looks like mtd can make use of this. > > We should be able to add this as an optional flag in nvmem_config to > enforce this check in case providers wanted to. > > Do you think that would help mtd nvmem case? Yes, it should work if nvmem cells are defined directly under the mtd node (or the partition they belong to). > Also I felt like nvmem-cells subnode seems to be a bit heavy! I still think grouping nvmem cells in a subnode is cleaner (just like we do for partitions), but I won't object if all parties (you, Alban and Rob) agree on this solution.
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