Re: [PATCH 02/11] media: iris: Add iris vpu bus support and register it with iommu_buses

[Dmitry Baryshkov]

On Tue, Apr 14, 2026 at 10:29:58AM +0530, Vishnu Reddy wrote:
> From: Vikash Garodia <vikash.garodia@xxxxxxxxxxxxxxxx>
> 
> Add a dedicated iris VPU bus type and register it into the iommu_buses
> list. Iris devices require their own bus so that each device can run its
> own dma_configure() logic.

This really tells nothing, unless one has full context about the Iris
needs. Start by describing the issue (that the device needs to have
multiple devices talking to describe IOMMUs / VAs for several hardware
functions), then continue by describing what is needed from the IOMMU
subsys.

> 
> Signed-off-by: Vikash Garodia <vikash.garodia@xxxxxxxxxxxxxxxx>
> Signed-off-by: Vishnu Reddy <busanna.reddy@xxxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/iommu.c                           |  4 ++++
>  drivers/media/platform/qcom/iris/Makefile       |  4 ++++
>  drivers/media/platform/qcom/iris/iris_vpu_bus.c | 32 +++++++++++++++++++++++++
>  include/linux/iris_vpu_bus.h                    | 13 ++++++++++

How are you supposed to merge this? Through IOMMU tree? Through venus
tree? Can we add one single bus to the IOMMU code and use it for Iris,
Venus, FastRPC, host1x and all other device drivers which require
per-device DMA configuration?

Your colleagues from the FastRPC team posted a very similar code few
weeks ago and got exactly the same feedback. Is there a reason why your
teams don't sync on the IOMMU parts at all?

>  4 files changed, 53 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 61c12ba78206..d8ed6ef70ecd 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -13,6 +13,7 @@
>  #include <linux/bug.h>
>  #include <linux/types.h>
>  #include <linux/init.h>
> +#include <linux/iris_vpu_bus.h>
>  #include <linux/export.h>
>  #include <linux/slab.h>
>  #include <linux/errno.h>
> @@ -179,6 +180,9 @@ static const struct bus_type * const iommu_buses[] = {
>  #ifdef CONFIG_CDX_BUS
>  	&cdx_bus_type,
>  #endif
> +#if IS_ENABLED(CONFIG_VIDEO_QCOM_IRIS)
> +	&iris_vpu_bus_type,
> +#endif
>  };
>  
>  /*
> diff --git a/drivers/media/platform/qcom/iris/Makefile b/drivers/media/platform/qcom/iris/Makefile
> index 2abbd3aeb4af..6f4052b98491 100644
> --- a/drivers/media/platform/qcom/iris/Makefile
> +++ b/drivers/media/platform/qcom/iris/Makefile
> @@ -31,3 +31,7 @@ qcom-iris-objs += iris_platform_gen1.o
>  endif
>  
>  obj-$(CONFIG_VIDEO_QCOM_IRIS) += qcom-iris.o
> +
> +ifdef CONFIG_VIDEO_QCOM_IRIS
> +obj-y += iris_vpu_bus.o
> +endif
> diff --git a/drivers/media/platform/qcom/iris/iris_vpu_bus.c b/drivers/media/platform/qcom/iris/iris_vpu_bus.c
> new file mode 100644
> index 000000000000..b51bb4b82b0e
> --- /dev/null
> +++ b/drivers/media/platform/qcom/iris/iris_vpu_bus.c
> @@ -0,0 +1,32 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/of_device.h>
> +
> +#include "iris_platform_common.h"
> +
> +static int iris_vpu_bus_dma_configure(struct device *dev)
> +{
> +	const u32 *f_id = dev_get_drvdata(dev);
> +
> +	if (!f_id)
> +		return -ENODEV;
> +
> +	return of_dma_configure_id(dev, dev->parent->of_node, true, f_id);

I think it was discussed that this is not enough. Some of devices need
multiple function IDs.

> +}
> +
> +const struct bus_type iris_vpu_bus_type = {
> +	.name = "iris-vpu-bus",
> +	.dma_configure = iris_vpu_bus_dma_configure,
> +};
> +EXPORT_SYMBOL_GPL(iris_vpu_bus_type);
> +
> +static int __init iris_vpu_bus_init(void)
> +{
> +	return bus_register(&iris_vpu_bus_type);
> +}
> +
> +postcore_initcall(iris_vpu_bus_init);
> diff --git a/include/linux/iris_vpu_bus.h b/include/linux/iris_vpu_bus.h
> new file mode 100644
> index 000000000000..5704b226f7d6
> --- /dev/null
> +++ b/include/linux/iris_vpu_bus.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#ifndef __IRIS_VPU_BUS_H__
> +#define __IRIS_VPU_BUS_H__
> +
> +#if IS_ENABLED(CONFIG_VIDEO_QCOM_IRIS)
> +extern const struct bus_type iris_vpu_bus_type;
> +#endif
> +
> +#endif /* __IRIS_VPU_BUS_H__ */
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry