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Message-ID: <8bf182b1-e05f-0c90-a358-e5c8bf6bd430@quicinc.com>
Date: Thu, 29 Feb 2024 20:39:11 +0530
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Subject: Re: [PATCH v2 00/34] Qualcomm video encoder and decoder driver
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To: Hans Verkuil <hans.verkuil@cisco.com>, <mchehab@kernel.org>,
        <stanimir.k.varbanov@gmail.com>, <andersson@kernel.org>,
        <konrad.dybcio@linaro.org>, <bryan.odonoghue@linaro.org>,
        <agross@kernel.org>, <linux-media@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
CC: <linux-arm-msm@vger.kernel.org>, <quic_abhinavk@quicinc.com>,
        "Dikshita
 Agarwal" <quic_dikshita@quicinc.com>
References: <1702899149-21321-1-git-send-email-quic_dikshita@quicinc.com>
From: Vikash Garodia <quic_vgarodia@quicinc.com>
In-Reply-To: <1702899149-21321-1-git-send-email-quic_dikshita@quicinc.com>
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Hello All,

On 12/18/2023 5:01 PM, Dikshita Agarwal wrote:
> This patch series introduces support for Qualcomm new video acceleration
> hardware architecture, used for video stream decoding/encoding. This driver
> is based on new communication protocol between video hardware and application
> processor.
> This driver comes with below capabilities:
> - V4L2 complaint video driver with M2M and STREAMING capability.
> - Supports H264, H265, VP9 decoders.
> - Supports H264, H265 encoders.
> This driver comes with below features:
> - Centralized resource and memory management.
> - Centralized management of core and instance states.
> - Defines platform specific capabilities and features. As a results, it provides
>   a single point of control to enable/disable a given feature depending on 
>   specific platform capabilities.
> - Handles hardware interdependent configurations. For a given configuration from
>   client, the driver checks for hardware dependent configuration/s and updates
>   the same.
> - Handles multiple complex video scenarios involving state transitions - DRC,
>   Drain, Seek, back to back DRC, DRC during Drain sequence, DRC during Seek
>   sequence.
> - Introduces a flexible way for driver to subscribe for any property with
>   hardware. Hardware would inform driver with those subscribed property with any
>   change in value.
> - Introduces performance (clock and bus) model based on new hardware
>   architecture.
> - Introduces multi thread safe design to handle communication between client and
>   hardware.
> - Adapts encoder quality improvements available in new hardware architecture.
> - Implements asynchronous communication with hardware to achieve better
>   experience in low latency usecases.
> - Supports multi stage hardware architecture for encode/decode.
> - Output and capture planes are controlled independently. Thereby providing a
>   way to reconfigure individual plane.
> - Hardware packetization layer supports synchronization between configuration
>   packet and data packet.
> - Introduces a flexibility to receive a hardware response for a given command
>   packet.
> - Native hardware support of LAST flag which is mandatory to align with port
>   reconfiguration and DRAIN sequence as per V4L guidelines.
> - Native hardware support for drain sequence.

1. We considered enhancing the venus driver to support iris functionality but
concluded that the result would essentially be two parallel drivers implemented
in the same folder.
2. Although the underlying hardware for venus and iris are quite similar, but
there are other factors which brings the need of new driver:
   a. the host firmware interface (HFI) changed between the two. Venus supports
HFI protocol 1.0 while iris supports HFI protocol 2.0.
   b. unlike HFI protocol 1.0, HFI protocol 2.0 is better aligned to V4L2 APIs.
   c. iris driver modularize platforms, hardware variants, and states to extend
it for any upcoming SOC. Thereby more extendable to newer SOCs in future.
   d. Iris also supports many advanced features.
3. Based on the comments received on posted iris driver [1], we evaluated it
further and to better align with the upstream standard and practices, we
acknowledge that even though iris driver is the way forward, it would be ideal
to bring in the Venus hardwares enabled in this driver.
4. Hence, we decided to rework iris driver to add support of HFI protocol 1.0 as
well.
5. Initially we would start with adding support for one HFI protocol 1.0 based
platform which would be SM8250.
6. SM8250 enablement on iris driver would be incremental, starting with basic
decode for H264 codec.
7. In long-term, all venus supported platforms would be migrated to iris.
8. Iris driver and venus driver will co-exist till remaining supported targets
also gets migrated to iris driver.
9. We would continue to support and maintain venus driver during this phased out
approach.

Please share your thoughts on the above proposal.

[1]
https://patchwork.kernel.org/project/linux-media/cover/1702899149-21321-1-git-send-email-quic_dikshita@quicinc.com/#25643473

Regards,
Vikash