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

[Vishnu Reddy <busanna.reddy@oss.qualcomm.com>]

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@oss.qualcomm.com>
>>>
>>> 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@oss.qualcomm.com>
>>> Signed-off-by: Vishnu Reddy<busanna.reddy@oss.qualcomm.com>
>>> ---
>>>   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
>>>