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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A40E0C433E9 for ; Tue, 5 Jan 2021 07:18:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5259122838 for ; Tue, 5 Jan 2021 07:18:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726528AbhAEHR7 (ORCPT ); Tue, 5 Jan 2021 02:17:59 -0500 Received: from mga09.intel.com ([134.134.136.24]:40879 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725939AbhAEHR6 (ORCPT ); Tue, 5 Jan 2021 02:17:58 -0500 IronPort-SDR: rxbnynCdOMmcaghjfo9jMnTK4yHs8tIgvhwssnyrVBWqzfR58AqWa8sBxgVnNIeRZGnSg2W65D lb/oRUYoCZBw== X-IronPort-AV: E=McAfee;i="6000,8403,9854"; a="177217348" X-IronPort-AV: E=Sophos;i="5.78,476,1599548400"; d="scan'208";a="177217348" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Jan 2021 23:17:17 -0800 IronPort-SDR: HLSXPmG/ebpymc5Cm5QUhu0Wx8yLFzlA89q0sMQI7czP2tHmZe4zZ//NvWy5o34vKgqefzg161 uinHppj4AHOA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,476,1599548400"; d="scan'208";a="462210163" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.94]) ([10.237.72.94]) by fmsmga001.fm.intel.com with ESMTP; 04 Jan 2021 23:17:09 -0800 Subject: Re: [PATCH RFC v4 1/1] scsi: ufs: Fix ufs power down/on specs violation To: Bjorn Andersson Cc: Ziqi Chen , asutoshd@codeaurora.org, nguyenb@codeaurora.org, cang@codeaurora.org, hongwus@codeaurora.org, rnayak@codeaurora.org, vinholikatti@gmail.com, jejb@linux.vnet.ibm.com, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, kernel-team@android.com, saravanak@google.com, salyzyn@google.com, kwmad.kim@samsung.com, stanley.chu@mediatek.com, Alim Akhtar , Avri Altman , "James E.J. Bottomley" , Andy Gross , Matthias Brugger , Bean Huo , Bart Van Assche , Satya Tangirala , "moderated list:UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER..." , open list , "open list:ARM/QUALCOMM SUPPORT" , "moderated list:ARM/Mediatek SoC support" References: <1608644981-46267-1-git-send-email-ziqichen@codeaurora.org> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: Date: Tue, 5 Jan 2021 09:16:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/01/21 8:55 pm, Bjorn Andersson wrote: > On Mon 04 Jan 03:15 CST 2021, Adrian Hunter wrote: > >> On 22/12/20 3:49 pm, Ziqi Chen wrote: >>> As per specs, e.g, JESD220E chapter 7.2, while powering >>> off/on the ufs device, RST_N signal and REF_CLK signal >>> should be between VSS(Ground) and VCCQ/VCCQ2. >>> >>> To flexibly control device reset line, refactor the function >>> ufschd_vops_device_reset(sturct ufs_hba *hba) to ufshcd_ >>> vops_device_reset(sturct ufs_hba *hba, bool asserted). The >>> new parameter "bool asserted" is used to separate device reset >>> line pulling down from pulling up. >> >> This patch assumes the power is controlled by voltage regulators, but for us >> it is controlled by firmware (ACPI), so it is not correct to change RST_n >> for all host controllers as you are doing. >> >> Also we might need to use a firmware interface for device reset, in which >> case the 'asserted' value doe not make sense. >> > > Are you saying that the entire flip-flop-the-reset is a single firmware > operation in your case? Yes > If you look at the Mediatek driver, the > implementation of ufs_mtk_device_reset_ctrl() is a jump to firmware. > > > But perhaps "asserted" isn't the appropriate English word for saying > "the reset is in the resetting state"? > > I just wanted to avoid the use of "high"/"lo" as if you look at the > Mediatek code they pass the expected line-level to the firmware, while > in the Qualcomm code we pass the logical state to the GPIO code which is > setup up as "active low" and thereby flip the meaning before hitting the > pad. > >> Can we leave the device reset callback alone, and instead introduce a new >> variant operation for setting RST_n to match voltage regulator power changes? > > Wouldn't this new function just have to look like the proposed patches? > In which case for existing platforms we'd have both? > > How would you implement this, or would you simply skip implementing > this? Functionally, doing a device reset is not the same as adjusting signal levels to meet power up/off ramp requirements. However, the issue is that we do not use regulators, so the power is not necessarily being changed at those points, and we definitely do not want to reset instead of entering DeepSleep for example. Off the top of my head, I imagine something like a callback called ufshcd_vops_prepare_power_ramp(hba, bool on) which is called only if hba->vreg_info->vcc is not NULL.