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

Vishnu Reddy
2026-04-20T14:02:37Z

On 4/17/2026 11:49 PM, Dmitry Baryshkov wrote:
> On Fri, Apr 17, 2026 at 08:29:21PM +0530, Vishnu Reddy wrote:
>> apologies for re-sending (earlier responses was rejected due to HTML format)
> Ugh.
>
>> 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.
> Then why wasn't it done from the ground up?
>
>>>> 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.
> Why can't we land the version that has multiple entries? It's as if the
> teams are totally not in sync. The corresponding version is in works, it
> has been implemented, etc.
The main idea is to introduce firmware stream ID with iommu-map, while keeping the
other stream IDs described in legacy iommus way.
or, are you suggesting that, going forward, we should have VPU stream IDs described
_only_ with iommu-map for any new dts/bindings?

Thanks,
Vishnu Reddy.