linux-kernel - Re: [PATCH 2/6] iommu/arm-smmu-qcom: Add support for TBUs

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Message-ID: <1cdc2a68-a1e8-4cf2-8a1a-899d14f8db80@linaro.org>
Date:   Thu, 19 Oct 2023 13:13:34 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Georgi Djakov <quic_c_gdjako@...cinc.com>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        will@...nel.org, robin.murphy@....com, joro@...tes.org
Cc:     devicetree@...r.kernel.org, andersson@...nel.org,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        quic_cgoldswo@...cinc.com, quic_sukadev@...cinc.com,
        quic_pdaly@...cinc.com, quic_sudaraja@...cinc.com,
        djakov@...nel.org
Subject: Re: [PATCH 2/6] iommu/arm-smmu-qcom: Add support for TBUs



On 10/19/23 04:19, Georgi Djakov wrote:
> The ARM MMU-500 implements a Translation Buffer Unit (TBU) for each
> connected master besides a single TCU which controls and manages the
> address translations.
> 
> Allow the Qualcomm SMMU driver to probe for any TBU devices that can
> provide additional debug features like triggering transactions, logging
> outstanding transactions, snapshot capture etc. The most basic use-case
> would be to get information from the TBUs and print it during a context
> fault.
> 
> Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
> ---
>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 12 ++++++++++++
>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h |  4 +++-
>   2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 7f52ac67495f..655c7f50ca84 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -1,12 +1,14 @@
>   // SPDX-License-Identifier: GPL-2.0-only
>   /*
>    * Copyright (c) 2019, The Linux Foundation. All rights reserved.
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
>    */
>   
>   #include <linux/acpi.h>
>   #include <linux/adreno-smmu-priv.h>
>   #include <linux/delay.h>
>   #include <linux/of_device.h>
> +#include <linux/of_platform.h>
>   #include <linux/firmware/qcom/qcom_scm.h>
>   
>   #include "arm-smmu.h"
> @@ -466,6 +468,16 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
>   	qsmmu->smmu.impl = impl;
>   	qsmmu->cfg = data->cfg;
>   
> +	/* Populate TBU devices if such are present in DT */
> +	if (np && of_device_is_compatible(np, "arm,mmu-500")) {
I'd say this can be unconditional.

> +		int ret;
> +
> +		INIT_LIST_HEAD(&qsmmu->tbu_list);
This list is unused.

Konrad