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=-6.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 1D581C433E6 for ; Fri, 15 Jan 2021 05:59:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1B0A23AAA for ; Fri, 15 Jan 2021 05:59:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728269AbhAOF6v (ORCPT ); Fri, 15 Jan 2021 00:58:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:49936 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726019AbhAOF6u (ORCPT ); Fri, 15 Jan 2021 00:58:50 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 66736239EF; Fri, 15 Jan 2021 05:58:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610690290; bh=A2xQvZI3cYjFP3+C40z6oPKeq/38VezRg4M7YK6TvpI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ibY2R7ceYe8BqE2hj3mA8qlr2b7m8kLBYZN94Gn+IyG1ykTEfHq32oi7J3Hv7lrOc 1PuWhBRo9FLeuYe5eoX40NDoJvHMIVBNgH9cJ+1rQHwvkMk1/6pjNisMlHVLBPowp1 H54rJcRkH44Wwp1kEtO7qae8Q/HYEGhCdoYStdStZHF/cCDRZmvSMifAhAZMU6YJie E+S5SkCCfwa40egM9HuwiQz5y+YBc8/z79BxZFTplR45BukmDpJns7WyqxHpFhWN9O Q48TNyn+4wIijVkyGSwc+e6asL3nIINHvbhk+MSOoTs62AuaKwTBsD4srhbTmi9Y/M 9iL3BwSb7XH0w== Date: Fri, 15 Jan 2021 11:28:06 +0530 From: Vinod Koul To: mdalam@codeaurora.org Cc: corbet@lwn.net, agross@kernel.org, bjorn.andersson@linaro.org, dan.j.williams@intel.com, dmaengine@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, sricharan@codeaurora.org, mdalam=codeaurora.org@codeaurora.org Subject: Re: [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support Message-ID: <20210115055806.GE2771@vkoul-mobl> References: <1608215842-15381-1-git-send-email-mdalam@codeaurora.org> <20201221092355.GA3323@vkoul-mobl> <20210112101056.GI2771@vkoul-mobl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On 14-01-21, 01:20, mdalam@codeaurora.org wrote: > On 2021-01-12 15:40, Vinod Koul wrote: > > On 12-01-21, 15:01, mdalam@codeaurora.org wrote: > > > On 2020-12-21 23:03, mdalam@codeaurora.org wrote: > > > > On 2020-12-21 14:53, Vinod Koul wrote: > > > > > Hello, > > > > > > > > > > On 17-12-20, 20:07, Md Sadre Alam wrote: > > > > > > This change will add support for LOCK & UNLOCK flag bit support > > > > > > on CMD descriptor. > > > > > > > > > > > > If DMA_PREP_LOCK flag passed in prep_slave_sg then requester of this > > > > > > transaction wanted to lock the DMA controller for this transaction so > > > > > > BAM driver should set LOCK bit for the HW descriptor. > > > > > > > > > > > > If DMA_PREP_UNLOCK flag passed in prep_slave_sg then requester > > > > > > of this > > > > > > transaction wanted to unlock the DMA controller.so BAM driver > > > > > > should set > > > > > > UNLOCK bit for the HW descriptor. > > > > > > > > > > Can you explain why would we need to first lock and then unlock..? How > > > > > would this be used in real world. > > > > > > > > > > I have read a bit of documentation but is unclear to me. Also should > > > > > this be exposed as an API to users, sounds like internal to driver..? > > > > > > > > > > > > > IPQ5018 SoC having only one Crypto Hardware Engine. This Crypto Hardware > > > > Engine > > > > will be shared between A53 core & ubi32 core. There is two separate > > > > driver dedicated > > > > to A53 core and ubi32 core. So to use Crypto Hardware Engine > > > > parallelly for encryption/description > > > > we need bam locking mechanism. if one driver will submit the request > > > > for encryption/description > > > > to Crypto then first it has to set LOCK flag bit on command descriptor > > > > so that other pipes will > > > > get locked. > > > > > > > > The Pipe Locking/Unlocking will be only on command-descriptor. Upon > > > > encountering a command descriptor > > > > Can you explain what is a cmd descriptor? > > In BAM pipe descriptor structure there is a field called CMD (Command > descriptor). > CMD allows the SW to create descriptors of type Command which does not > generate any data transmissions > but configures registers in the Peripheral (write operations, and read > registers operations ). > Using command descriptor enables the SW to queue new configurations > between data transfers in advance. What and when is the CMD descriptor used for..? > > > > > > with LOCK bit set, The BAM will lock all other pipes not related to > > > > the current pipe group, and keep > > > > handling the current pipe only until it sees the UNLOCK set then it > > > > will release all locked pipes. > > > > locked pipe will not fetch new descriptors even if it got event/events > > > > adding more descriptors for > > > > this pipe (locked pipe). > > > > > > > > No need to expose as an API to user because its internal to driver, so > > > > while preparing command descriptor > > > > just we have to update the LOCK/UNLOCK flag. > > > > So IIUC, no api right? it would be internal to driver..? > > Yes its totally internal to deriver. So no need for this patch then, right? -- ~Vinod