linux-kernel - Re: [PATCH 2/2] iommu/arm-smmu: Allow client devices to select direct mapping

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Date:   Tue, 14 Apr 2020 21:48:37 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Evan Green <evgreen@...omium.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Rob Clark <robdclark@...il.com>,
        iommu@...ts.linux-foundation.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Tomasz Figa <tfiga@...omium.org>
Subject: Re: [PATCH 2/2] iommu/arm-smmu: Allow client devices to select direct
 mapping

Hi Evan,

On 2020-04-14 04:42, Evan Green wrote:
> On Wed, Jan 22, 2020 at 3:48 AM Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>> 
>> From: Jordan Crouse <jcrouse@...eaurora.org>
>> 
>> Some client devices want to directly map the IOMMU themselves instead
>> of using the DMA domain. Allow those devices to opt in to direct
>> mapping by way of a list of compatible strings.
>> 
>> Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
>> Co-developed-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>> ---
>>  drivers/iommu/arm-smmu-qcom.c | 39 
>> +++++++++++++++++++++++++++++++++++
>>  drivers/iommu/arm-smmu.c      |  3 +++
>>  drivers/iommu/arm-smmu.h      |  5 +++++
>>  3 files changed, 47 insertions(+)
>> 
>> diff --git a/drivers/iommu/arm-smmu-qcom.c 
>> b/drivers/iommu/arm-smmu-qcom.c
>> index 64a4ab270ab7..ff746acd1c81 100644
>> --- a/drivers/iommu/arm-smmu-qcom.c
>> +++ b/drivers/iommu/arm-smmu-qcom.c
>> @@ -3,6 +3,7 @@
>>   * Copyright (c) 2019, The Linux Foundation. All rights reserved.
>>   */
>> 
>> +#include <linux/of_device.h>
>>  #include <linux/qcom_scm.h>
>> 
>>  #include "arm-smmu.h"
>> @@ -11,6 +12,43 @@ struct qcom_smmu {
>>         struct arm_smmu_device smmu;
>>  };
>> 
>> +static const struct arm_smmu_client_match_data qcom_adreno = {
>> +       .direct_mapping = true,
>> +};
>> +
>> +static const struct arm_smmu_client_match_data qcom_mdss = {
>> +       .direct_mapping = true,
> 
> I don't actually see direct_mapping being used. Shouldn't this member
> be checked somewhere?
> 

Thanks for spotting this, my bad. It should be checked in 
qcom_smmu_request_domain().

diff --git a/drivers/iommu/arm-smmu-qcom.c 
b/drivers/iommu/arm-smmu-qcom.c
index ff746acd1c81..3ff62ca13ad5 100644
--- a/drivers/iommu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm-smmu-qcom.c
@@ -43,7 +43,7 @@ static int qcom_smmu_request_domain(struct device 
*dev)
         const struct arm_smmu_client_match_data *client;

         client = qcom_smmu_client_data(dev);
-       if (client)
+       if (client && client->direct_mapping)
                 iommu_request_dm_for_dev(dev);

         return 0;

-Sai

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