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

[Vishnu Reddy]

apologies for re-sending (earlier responses was rejected due to HTML format)

On 4/17/2026 8:22 PM, Vishnu Reddy wrote:
> On 4/14/2026 8:44 PM, Dmitry Baryshkov wrote:
> > 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.
>
> This series handles firmware device which do not require multiple 
> devices part.
> given this device need for specific IOMMU configuration, I'll update 
> the description
> accordingly.
>
> > > 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?
>
> Separating out the bus definition and the Iris driver handling would 
> provide a
> cleaner merge path.
>
> > 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?
>
> I would admit that I missed to review that, thank you for bringing 
> that discussion.
> FastRPC patches generalizes the handling for host1x, FastRPC and the 
> same can be
> extended for Iris. I have left few comments there.
>
> > >   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.
>
> In this glymur series we are following the legacy way of handling 
> IOMMUs and does not
> require multi map.
>
> Thanks,
> Vishnu Reddy.
>
> > > +}
> > > +
> > > +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