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Tue, 27 Oct 2020 05:16:09 -0700 (PDT) X-Gm-Message-State: AOAM5322FpkW1pbFklaNEBshaUd+YDgXTHnjr/IfHjyZVU3ZdXI1Hp0A d1xS1JDhxviHDp1cJodUs4dtpz9s3HbeHDx3mw== X-Google-Smtp-Source: ABdhPJwWNPIQlF6Bp7SJfw0BWlotFu1Nk1SaBiaHNR8Jk/NmGn35wJqO0jl1Ihg5ANtyL/n3D9IZ22eRLIBU/rPXk3E= X-Received: by 2002:a4a:d453:: with SMTP id p19mr1528328oos.50.1603800968782; Tue, 27 Oct 2020 05:16:08 -0700 (PDT) MIME-Version: 1.0 References: <20201021102855.18026-1-a.fatoum@pengutronix.de> <20201026143656.GA118160@bogus> <23e423ba-25f2-c3ed-ea65-2c2d86ae9522@pengutronix.de> In-Reply-To: <23e423ba-25f2-c3ed-ea65-2c2d86ae9522@pengutronix.de> From: Rob Herring Date: Tue, 27 Oct 2020 07:15:57 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/2] dt-bindings: arm: stm32: add simple-mfd compatible for tamp node To: Ahmad Fatoum X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201027_081612_516421_E89271ED X-CRM114-Status: GOOD ( 22.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, Alexandre Torgue , Arnaud Pouliquen , "linux-kernel@vger.kernel.org" , "moderated list:ARM/STM32 ARCHITECTURE" , linux-arm-kernel , Sascha Hauer , Christophe Roullier , Maxime Coquelin Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 26, 2020 at 4:30 PM Ahmad Fatoum wrote: > > Hello Rob, > > On 10/26/20 3:36 PM, Rob Herring wrote: > > On Wed, Oct 21, 2020 at 12:28:55PM +0200, Ahmad Fatoum wrote: > >> The stm32mp1 TAMP (Tamper and backup registers) does tamper detection > >> and features 32 backup registers that, being in the RTC domain, may > >> survive even with Vdd switched off. > >> > >> This makes it suitable for use to communicate a reboot mode from OS > >> to bootloader via the syscon-reboot-mode binding. Add a "simple-mfd" > >> to support probing such a child node. The actual reboot mode > >> node could then be defined in a board.dts or fixed up by the bootloader. > > > > 'simple-mfd' implies there is no dependency on the parent node for the > > child (such as the regmap perhaps). Is that the case here? > > No, there's a dependency and the Linux driver does syscon_node_to_regmap > on the device tree node's parent but that's how the syscon-reboot-mode binding > is documented: > > The SYSCON mapped register is retrieved from the > parental dt-node plus the offset. So the SYSCON reboot-mode node > should be represented as a sub-node of a "syscon", "simple-mfd" node. > > How would you prefer this being done instead? Well, probably the syscon driver could just probe any children, but I'm not sure if that would break anyone. So I guess fine as-is. Reviewed-by: Rob Herring Rob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel