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From: Robin Murphy <robin.murphy@arm.com>
To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: ohad@wizery.com, devicetree@vger.kernel.org,
	linux-kernel-owner@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org,
	linux-kernel@vger.kernel.org, bjorn.andersson@linaro.org,
	iommu@lists.linux-foundation.org, robh+dt@kernel.org,
	Sibi Sankar <sibis@codeaurora.org>,
	agross@kernel.org
Subject: Re: [PATCH 0/3] Request direct mapping for modem firmware subdevice
Date: Thu, 12 Mar 2020 12:05:00 +0000
Message-ID: <497e40b8-300f-1b83-4312-93a58c459d1d@arm.com> (raw)
In-Reply-To: <ff805c5c647326c5edaddf2efec5cb87@codeaurora.org>

On 2020-03-12 6:28 am, Sai Prakash Ranjan wrote:
> Hi Robin,
> 
> On 2020-03-10 22:14, Robin Murphy wrote:
>> On 10/03/2020 4:23 pm, Joerg Roedel wrote:
>>> On Tue, Mar 10, 2020 at 07:30:50PM +0530, Sibi Sankar wrote:
>>>> 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).
>>>
>>> Okay, this sounds like a case for arm_smmu_get_resv_region(). It should
>>> return an entry for the reserved memory region the firmware needs to
>>> access, so that generic iommu can setup this mapping.
>>>
>>> Note that it should return that entry only for your device, not for all
>>> devices. Maybe there is a property in DT or IORT you can set to
>>> transport this information into the arm-smmu driver.
>>>
>>> This is pretty similar to RMRR mapping on the Intel VT-d IOMMU or
>>> Unity-mapped ranges in the AMD-Vi IOMMU.
>>
>> Yup, a way to describe boot-time memory regions in IORT is in the
>> process of being specced out; the first attempt at an equivalent for
>> DT is here:
>>
>> https://lore.kernel.org/linux-iommu/20191209150748.2471814-1-thierry.reding@gmail.com/ 
>>
>>
>> If that's not enough and the SMMU still needs to treat certain Stream
>> IDs specially because they may be untranslatable (due to having direct
>> access to memory as a side-channel), then that should be handled in
>> the SoC-specific corner of the SMMU driver, not delegated to
>> individual endpoint drivers.
>>
> 
> Are you talking about this one for SoC specific change - 
> https://lore.kernel.org/patchwork/patch/1183530/

Exactly - this particular wheel needs no reinventing at all.

[ I guess I should go review those patches properly... :) ]

Robin.

  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
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 [this message]
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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