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[209.85.166.180]) by smtp.gmail.com with ESMTPSA id q6-20020a0566380d0600b0040474ab909fsm3378382jaj.36.2023.04.24.11.15.08 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Apr 2023 11:15:09 -0700 (PDT) Received: by mail-il1-f180.google.com with SMTP id e9e14a558f8ab-328cb023b1dso1095145ab.0 for ; Mon, 24 Apr 2023 11:15:08 -0700 (PDT) X-Received: by 2002:a05:6e02:1d09:b0:32e:561d:b42d with SMTP id i9-20020a056e021d0900b0032e561db42dmr34592ila.16.1682360107716; Mon, 24 Apr 2023 11:15:07 -0700 (PDT) MIME-Version: 1.0 References: <20230418124953.3170028-1-fshao@chromium.org> <20230418124953.3170028-2-fshao@chromium.org> In-Reply-To: From: Doug Anderson Date: Mon, 24 Apr 2023 11:14:55 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/2] dt-bindings: input: goodix: Add powered-in-suspend property To: Jeff LaBundy Cc: Fei Shao , Benjamin Tissoires , Rob Herring , linux-mediatek , Dmitry Torokhov , Krzysztof Kozlowski , devicetree@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi, On Sun, Apr 23, 2023 at 8:31=E2=80=AFPM Jeff LaBundy wro= te: > > Back-powering can come in two forms: > > 1. The one you've described, which is by far the most common. As you ment= ion, > it is not the case here since the issue happens only when we drive the GP= IO > low and not high. > > 2. Through a forbidden power supply sequence, an input pin of an IC with > multiple power supplies becomes a weak power supply itself. Grounding the > GPIO then sinks current into the SoC. > > This problem smelled like (2), especially since asserting the GPIO or pow= ering > down the supply alleviates the symptom. Most Goodix controllers I've work= ed > with have two or more supplies, and the datasheet requires them to be ena= bled > or disabled in a specific order. > > Based on Fei's feedback, however, this IC does not seem to be one of thos= e > since there is reportedly only a single rail. I guess either vdd or vddio= is > tied to a dummy regulator? If so, then perhaps we can scratch this theory= . There is one rail provided from the main board, but there can be two voltage levels involved depending on stuffings on the touchscreen itself. I talked a bit about this in commit 1d18c1f3b7d9 ("dt-bindings: HID: i2c-hid: goodix: Add mainboard-vddio-supply"). > Fair enough, I was simply sketpical that this was the _right_ workaround. > Were this an issue of only supply A left on yet the IC datasheet requires > supply B to remain on if supply A is on, I would rather see this solved b= y > updating a regulator dts node, trusted FW sequence, etc. Right. That type of stuff was looked at in detail by two separate teams, so I don't think this is the issue. > Thanks for your due diligence; if this really is a silicon issue, then > the driver should indeed accommodate it. > > That being said, the name 'powered-in-suspend' seems a bit conflated. We > should not be duplicating regulator policy in this driver; the existing > naming also may cause confusion for other HW configurations that do leave > vdd and vddio on during suspend, but don't have this problem. > > Here, we actually mean to control the behavior of the reset GPIO through > suspend and therefore something like 'goodix,no-reset-during-suspend' is > closer to what I understand us to intend to do. I will add more details > in patch [2/2]. I'd be fine with that name. ...ah, and adding the "goodix," prefix is a good call. -Doug