From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC2B8C433FE for ; Thu, 3 Nov 2022 12:29:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229791AbiKCM3A (ORCPT ); Thu, 3 Nov 2022 08:29:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230017AbiKCM27 (ORCPT ); Thu, 3 Nov 2022 08:28:59 -0400 Received: from mail-pg1-x52e.google.com (mail-pg1-x52e.google.com [IPv6:2607:f8b0:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A35FEBF44 for ; Thu, 3 Nov 2022 05:28:58 -0700 (PDT) Received: by mail-pg1-x52e.google.com with SMTP id h193so1505896pgc.10 for ; Thu, 03 Nov 2022 05:28:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=pvgX6ikZPni7jkpkvXbOwi0lz3HvKft3SvDqE9pJ2xU=; b=WyrnXRZT3Uw1ORHTuUhT8HNqidfzc/clXoM6HVa5dwhaCAmIj1oPOdCbKnG9YHBil7 eZ2jqBre98HZk2J35iQkISx7sC1/cOcB5nb+ZNqGNBQDjMdCrbPoB5S+tv6239aE8V1s k89s6rvO0CtOC+GQC4xOk04j48iZ59MnDgK+RPP0DV6ANxWkmLwjOlo1pNYkmm+8KTHK 40UAHkuEOGZU/xlGA6kkT6iz1JPcu4UTjKgCsS0UmCSoqKLNBGa4I4MYSdQZ2UW9pKtn rk3dVMHGJOzkCVFSXE0f/Vz1Klf4uCdnz+V5Ejnzclqgb2dT0fgs8ISNUimcD7ZK79Q/ 6nlw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=pvgX6ikZPni7jkpkvXbOwi0lz3HvKft3SvDqE9pJ2xU=; b=VoesGOVJh+vm65uVZMsEGMoaxhobvi+7SZI6sU2xxcCYedyf96TA0Zattdfa46150d mtMOX93MLoMHsTXbKVFEpmvREGZNwTcu6NBks+vhsU87Nw/VtoJZB1Ud/gudv5jr4mf7 NtmGiAZt/DQduGwAk+Uo3TLjWlxAgVfNnT2ROQcCbRdfjpKXm3xxpdxylP3C6lCC1emY Rxi61vuFpvB9aoN9GVi/lzpB/anI5HgaAGVdQCbE4D3NeDzxc5i5YHvsRW0cy689yCvR 21NytZ3aoqL2G6O1qgaHVcSW8PWQqa3p9fCG1qyn268TD1tl3/j5X9gVJX86DxYcVzyM BfSQ== X-Gm-Message-State: ACrzQf2NaBySNOd26nrQciMMWjMpqwGI7lqkJSfq/2qFVIbkTVqEkxAg uX0K3AtI7VzfwNb21OmjA1rZ X-Google-Smtp-Source: AMsMyM7IgbklEQwLyfEerx5Y4/DIC4P9MoC9GwY02mCKjFxupeSyqgi6vMMbfF4T4PW2ljR+mFibkA== X-Received: by 2002:a63:4f09:0:b0:440:4706:2299 with SMTP id d9-20020a634f09000000b0044047062299mr26472031pgb.115.1667478538121; Thu, 03 Nov 2022 05:28:58 -0700 (PDT) Received: from thinkpad ([59.92.102.81]) by smtp.gmail.com with ESMTPSA id l12-20020a170903120c00b00172fad607b3sm510757plh.207.2022.11.03.05.28.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 05:28:57 -0700 (PDT) Date: Thu, 3 Nov 2022 17:58:50 +0530 From: Manivannan Sadhasivam To: Krzysztof Kozlowski Cc: martin.petersen@oracle.com, jejb@linux.ibm.com, andersson@kernel.org, vkoul@kernel.org, krzysztof.kozlowski+dt@linaro.org, konrad.dybcio@somainline.org, robh+dt@kernel.org, quic_cang@quicinc.com, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org, linux-scsi@vger.kernel.org, dmitry.baryshkov@linaro.org, ahalaney@redhat.com Subject: Re: [PATCH v2 06/15] dt-bindings: ufs: Add "max-device-gear" property for UFS device Message-ID: <20221103122850.GD8434@thinkpad> References: <20221031180217.32512-1-manivannan.sadhasivam@linaro.org> <20221031180217.32512-7-manivannan.sadhasivam@linaro.org> <1fe8fd96-7770-0bda-c970-aa38d030ff3b@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1fe8fd96-7770-0bda-c970-aa38d030ff3b@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Wed, Nov 02, 2022 at 03:09:50PM -0400, Krzysztof Kozlowski wrote: > On 31/10/2022 14:02, Manivannan Sadhasivam wrote: > > The maximum gear supported by the UFS device can be specified using the > > "max-device-gear" property. This allows the UFS controller to configure the > > TX/RX gear before starting communication with the UFS device. > > This is confusing. The UFS PHY provides gear capability, so what is the > "device" here? The attached memory? How could it report something else > than phy? > This is the norm with any storage protocol, right? Both host and device (memory) can support different speeds and the OEM can choose to put any combinations (even though it might not be very efficient). For instance, PHY (G4) -> Device (G3) >From the host perspective we know what the PHY can support but that's not the same with the device until probing it. And probing requires using a minimum supported gear. For sure we can use something like G2/G3 and reinit later but as I learnt, that approach was rejected by the community when submitted by Qualcomm earlier. > The last sentence also suggests that you statically encode gear to avoid > runtime negotiation. > Yes, the OEM should know what the max gear speed they want to run, so getting this info from DT makes sense. Thanks, Mani > Best regards, > Krzysztof > -- மணிவண்ணன் சதாசிவம்