From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: sibis=codeaurora.org@mg.codeaurora.org MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 10 Mar 2020 19:30:50 +0530 From: Sibi Sankar Subject: Re: [PATCH 0/3] Request direct mapping for modem firmware subdevice In-Reply-To: <20200310112332.GG3794@8bytes.org> References: <20200309182255.20142-1-sibis@codeaurora.org> <20200310112332.GG3794@8bytes.org> Message-ID: <4ed6ddd667a3e6f670084a443d141474@codeaurora.org> To: Joerg Roedel Cc: bjorn.andersson@linaro.org, robh+dt@kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, iommu@lists.linux-foundation.org, linux-remoteproc@vger.kernel.org, ohad@wizery.com, agross@kernel.org, linux-kernel-owner@vger.kernel.org List-ID: Hey Joerg, Thanks for taking time to review the series! On 2020-03-10 16:53, Joerg Roedel wrote: > On Mon, Mar 09, 2020 at 11:52:52PM +0530, Sibi Sankar wrote: >> The Q6 modem sub-system has direct access to DDR through memnoc and >> an indirect access routed through a SMMU which MSS CE (crypto engine >> sub-component of MSS) uses during out of reset sequence. Request >> direct >> mapping for the modem-firmware subdevice since smmu is not expected >> to provide access control/translation for these SIDs (sandboxing of >> the >> modem is achieved through XPUs engaged using SMC calls). > > So the DMA accesses are initiated by the firmware and need to be direct > mapped? Which memory region do they access? The accesses are initiated by the firmware and they access modem reserved regions. However as explained in ^^ any accesses outside the region will result in a violation and is controlled through XPUs (protection units). With ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT y the firmware SIDs will explicitly need to be directly mapped to avoid observing global faults in the absence of secure firmware (TrustZone) programming the modem SIDs as S2CR-Bypass. > > Regards, > > Joerg -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.