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[24.155.109.49]) by smtp.gmail.com with ESMTPSA id m2sm1164119oim.13.2019.12.18.12.34.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Dec 2019 12:34:04 -0800 (PST) Date: Wed, 18 Dec 2019 14:34:04 -0600 From: Rob Herring To: Xingyu Chen Cc: Guenter Roeck , Martin Blumenstingl , Wim Van Sebroeck , Kevin Hilman , Neil Armstrong , Qianggui Song , devicetree@vger.kernel.org, linux-watchdog@vger.kernel.org, Jianxin Pan , linux-kernel@vger.kernel.org, Jian Hu , linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, Jerome Brunet Subject: Re: [PATCH v5 2/4] dt-bindings: watchdog: add new binding for meson secure watchdog Message-ID: <20191218203404.GA2451@bogus> References: <1576153187-28378-1-git-send-email-xingyu.chen@amlogic.com> <1576153187-28378-3-git-send-email-xingyu.chen@amlogic.com> <1da513d7-20e1-726a-dcc4-952cbfbbe63a@amlogic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1da513d7-20e1-726a-dcc4-952cbfbbe63a@amlogic.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Wed, Dec 18, 2019 at 03:37:49PM +0800, Xingyu Chen wrote: > Hi, Guenter Martin > > On 2019/12/16 21:30, Guenter Roeck wrote: > > On 12/15/19 10:03 PM, Xingyu Chen wrote: > > > Hi, Martin > > > > > > Sorry for the late reply. > > > > > > On 2019/12/13 4:05, Martin Blumenstingl wrote: > > > > Hi Xingyu and Rob, > > > > > > > > On Thu, Dec 12, 2019 at 1:20 PM Xingyu Chen > > > > wrote: > > > > [...] > > > > > +examples: > > > > > +  - | > > > > > +    watchdog { > > > > > +          compatible = "amlogic,meson-sec-wdt"; > > > > > +          timeout-sec = <60>; > > > > > +    }; > > > > in v3 of this patch Rob commented that there shouldn't be an OF node > > > > if there are no additional properties > > > > with timeout-sec there's now an additional property so my > > > > understanding is that it's fine to have an OF node > > > Your understanding is correct. > > > > > > > > what I don't understand yet is where this node should be placed. > > > > is it supposed to be a child node of the secure monitor node (for > > > > which we already have a binding here: > > > > Documentation/devicetree/bindings/firmware/meson/meson_sm.txt) or > > > > where else would we place it inside the .dts? > > > IMO,  Although the watchdog node need to reference the meson_sm > > > node, there is no > > > bus-like dependencies between the devices which the two nodes > > > corresponding to. > > > so i think that the watchdog node as child node of meson_sm maybe > > > not appropriate. > > > > The watchdog driver needs the meson SM's dt node, and it depends on the > > existence > > of that node. That seems enough of a relationship to warrant having it > > as child note. > Thanks for your reply, if i take the wdt node as child of secure monitor > (sm), how should > i register or find the wdt device ? > > I only think of the following three methods : > 1). update the sm driver，and scan®ister wdt device when the sm driver > probes(It is like i2c), but there > are too many changes involved. Just add of_platform_default_populate() call and clean-up calls. That's not what I'd call 'too many changes'. > 2). add "simple-bus" key string to compatible of sm node, and it will make > the child node is registered as > platform device, but it seems that the key string is not match current > scene. You previously said it's not a bus... > > secure-monitor { >     compatible = "amlogic,meson-gxbb-sm",  "simple-bus"; > >     watchdog { >         compatible = "amlogic,meson-sec-wdt"; >         timeout-sec = <60>; >     } > } > > 3).  don't register device, and find directly the watchdog node by using the > of_* API in watchdog > driver (Eg: linux-4.x/drivers/tee/optee/core.c) > > secure-monitor { >     compatible = "amlogic,meson-gxbb-sm"; > >     watchdog { >         compatible = "amlogic,meson-sec-wdt"; >         timeout-sec = <60>; >     } > } > > The method 3 looks better for me, do you have a better suggestion ? Thanks > > BR > > > > Guenter > > > > . > >