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h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=bQ8sePp1UB/buB3CQpsdDQjSw45clnU/8Z5dyE7MCUQ=; b=NBVjkQrydZ4y9ltCPm9erUPYla3dSsGc++jI+nGQ16uwo8+X+KIFEnJBuDOahwvADd LwhbAIN+zTR8cBYmWqUX+kdZ0DMQlFq4Iimo4mevlQewXobBBDyyEmIZd+8xSUwcs6Tc LoQs85XXh2/0IW4r8invUcEaRR1zzLpYCyLXSRaKX9L5PvfU3E6LpVmc+xBu86BZXGUi gY+mYub17H4ywVFUdiQF6J2C8YERKYf9VERrFbKdXle1UH662JYwT/Vrx/hCbbgChTTB XQX46DQOoZtFmxFi54oWiMk3XR1kusj7hvLBcCz/UsnsnmkXKWuhknK2jQqzh4dW8NCb 8akw== X-Gm-Message-State: APjAAAXf4cPfQYHXd3wYYWZAoex9/ggO45cOT++lCtf08e07iGrnZ9di mG7P5wdG2JLD5E4bk7cA0XGDBKEX3j0ONHHxBH8qVD4Sdlo= X-Google-Smtp-Source: APXvYqw2JjwDeqMh2CT5SlyR30QLXuZPvZ+1N9eFdrRhTkkWcwjICSQnRUvYtFyz4OeBrSGR4GBFkA8sANeEtDRg/YU= X-Received: by 2002:a37:6551:: with SMTP id z78mr7090523qkb.144.1578523963679; Wed, 08 Jan 2020 14:52:43 -0800 (PST) MIME-Version: 1.0 References: <20200108052337.65916-1-drinkcat@chromium.org> <20200108052337.65916-5-drinkcat@chromium.org> <20200108132302.GA3817@sirena.org.uk> In-Reply-To: <20200108132302.GA3817@sirena.org.uk> From: Nicolas Boichat Date: Thu, 9 Jan 2020 06:52:32 +0800 Message-ID: Subject: Re: [PATCH v2 4/7] drm/panfrost: Add support for a second regulator for the GPU To: Mark Brown X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200108_145244_619664_52C26CEB X-CRM114-Status: GOOD ( 17.54 ) 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: Mark Rutland , Devicetree List , Tomeu Vizoso , David Airlie , lkml , Liam Girdwood , dri-devel@lists.freedesktop.org, Steven Price , Rob Herring , "moderated list:ARM/Mediatek SoC support" , Alyssa Rosenzweig , Daniel Vetter , Hsin-Yi Wang , Matthias Brugger , linux-arm Mailing List Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jan 8, 2020 at 9:23 PM Mark Brown wrote: > > On Wed, Jan 08, 2020 at 01:23:34PM +0800, Nicolas Boichat wrote: > > > Some GPUs, namely, the bifrost/g72 part on MT8183, have a second > > regulator for their SRAM, let's add support for that. > > > + pfdev->regulator_sram = devm_regulator_get_optional(pfdev->dev, "sram"); > > + if (IS_ERR(pfdev->regulator_sram)) { > > This supply is required for the devices that need it so I'd therefore > expect the driver to request the supply non-optionally based on the > compatible string rather than just hoping that a missing regulator isn't > important. That'd be a bit awkward to match, though... Currently all bifrost share the same compatible "arm,mali-bifrost", and it'd seem weird/wrong to match "mediatek,mt8183-mali" in this driver? I have no idea if any other Mali implementation will require a second regulator, but with the MT8183 we do need it, see below. > Though I do have to wonder given the lack of any active > management of the supply if this is *really* part of the GPU or if it's > more of a SoC thing, it's not clear what exactly adding this code is > achieving. Well if devfreq was working (see patch 7 https://patchwork.kernel.org/patch/11322851/ for a partial implementation), it would adjust both mali and sram regulators, see the OPP table in patch 2 (https://patchwork.kernel.org/patch/11322825/): SRAM voltage needs to be increased for frequencies >=698Mhz. Now if you have some better idea how to implement this, I'm all ears! Thanks. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel