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From: Sibi Sankar <sibis@codeaurora.org>
To: Joerg Roedel <joro@8bytes.org>
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
Subject: Re: [PATCH 0/3] Request direct mapping for modem firmware subdevice
Date: Tue, 10 Mar 2020 19:30:50 +0530
Message-ID: <4ed6ddd667a3e6f670084a443d141474@codeaurora.org> (raw)
In-Reply-To: <20200310112332.GG3794@8bytes.org>

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.

  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-09 18:22 Sibi Sankar
2020-03-09 18:22 ` [PATCH 1/3] iommu: Export "iommu_request_dm_for_dev" Sibi Sankar
2020-03-09 18:22 ` [PATCH 2/3] dt-bindings: remoteproc: qcom: Add modem-firmware bindings Sibi Sankar
2020-03-09 18:22 ` [PATCH 3/3] remoteproc: qcom_q6v5_mss: Request direct mapping for firmware subdevice Sibi Sankar
2020-03-10 11:23 ` [PATCH 0/3] Request direct mapping for modem " Joerg Roedel
2020-03-10 14:00   ` Sibi Sankar [this message]
2020-03-10 16:23     ` Joerg Roedel
2020-03-10 16:44       ` Robin Murphy
2020-03-12  6:28         ` Sai Prakash Ranjan
2020-03-12 12:05           ` Robin Murphy
2020-03-23  9:43             ` Sai Prakash Ranjan
2020-03-16 15:50 ` Christoph Hellwig
2020-03-16 16:37   ` Sibi Sankar

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