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[109.252.138.165]) by smtp.gmail.com with ESMTPSA id f30sm1433412lfj.112.2022.02.10.15.17.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Feb 2022 15:17:46 -0800 (PST) Date: Fri, 11 Feb 2022 02:17:39 +0300 From: Dmitry Osipenko To: Julius Werner Cc: Krzysztof Kozlowski , Rob Herring , linux-tegra@vger.kernel.org, Rob Herring , Jonathan Hunter , devicetree@vger.kernel.org, LKML , Thierry Reding Subject: Re: [PATCH v5 3/9] dt-bindings: memory: lpddr2: Add revision-id properties Message-ID: <20220211021739.14f3614c@dimatab> In-Reply-To: References: <20211006224659.21434-1-digetx@gmail.com> <20211006224659.21434-4-digetx@gmail.com> <6568fd31-113f-1581-4eff-45a4a1eb4e5d@canonical.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org =D0=92 Wed, 9 Feb 2022 16:32:25 -0800 Julius Werner =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > I don't mind, but I also don't see where the revision-id property of > > LPDDR3 is used at all. I can't find any device-tree with LPDDR3 > > revision-id and don't see it being used in the code either. Maybe > > it's the LPDDR3 binding that needs to be changed? =20 >=20 > We are using the revision ID in userspace (read through > /proc/device-tree) for runtime memory identification. We don't have a > kernel driver bound to it. Our boot firmware is inserting this value > at runtime into the FDT (that's basically the reason we have this, our > firmware auto-detects memory during boot and we use the FDT to report > what it found to userspace), that's why you can't find it anywhere in > the static device trees in boot/dts/. Thank you for the clarification. Which device is that and why userspace needs to know so much about memory? > > I made each LPDDR2 revision-id property to correspond to a > > dedicated MR of LPDDR, which feels okay to me to since it matches > > h/w. =20 >=20 > I'm not super married to my solution, so if that makes things easier > we can standardize on the two-property version as well. I mostly > designed it my way because I thought we may one day also want to do > something like this for the 8-byte LPDDR5 serial-id, and then it would > get kinda cumbersome to have serial-id1 through serial-id8 all as > separate properties. But that's also a bridge we can cross when we get > there. >=20 > My use case is in a position where we could still change this now > without requiring backwards-compatibility. Krzysztof, would you be > okay if I instead changed the "jedec,lpddr3" to the same thing > "jedec,lpddr2" does -- seeing as the original patch was from me, my > use case could handle the switch, there has never been any actual > kernel code using the property, and it seems very unlikely that anyone > else has silently started using the same thing in the time it's been > in the tree? Or do we also need to go the official deprecation route > for that? If you're going to use multiple cells for other properties, then indeed will be better to keep it consistent.