Date: Wed, 20 Dec 2023 10:39:52 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Vikash Garodia <quic_vgarodia@...cinc.com>
Cc: Dikshita Agarwal <quic_dikshita@...cinc.com>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stanimir.k.varbanov@...il.com, 
	agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org, 
	mchehab@...nel.org, bryan.odonoghue@...aro.org, linux-arm-msm@...r.kernel.org, 
	quic_abhinavk@...cinc.com
Subject: Re: [PATCH v2 00/34] Qualcomm video encoder and decoder driver

On Wed, 20 Dec 2023 at 10:14, Vikash Garodia <quic_vgarodia@...cinc.com> wrote:
>
> Hi,
>
> On 12/20/2023 1:07 PM, Dmitry Baryshkov wrote:
> > On Wed, 20 Dec 2023 at 08:32, Vikash Garodia <quic_vgarodia@...cinc.com> wrote:
> >>
> >> Hi Dmitry,
> >>
> >> On 12/19/2023 12:08 AM, Dmitry Baryshkov wrote:
> >>> On 18/12/2023 13:31, 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 doesn't answer one important point, you have been asked for v1. What is the
> >>> actual change point between Venus and Iris? What has been changed so much that
> >>> it demands a separate driver. This is the main question for the cover letter,
> >>> which has not been answered so far.
> >>>
> >>> From what I see from you bindings, the hardware is pretty close to what we see
> >>> in the latest venus generations. I asssme that there was a change in the vcodec
> >>> inteface to the firmware and other similar changes. Could you please point out,
> >>> which parts of Venus driver do no longer work or are not applicable for sm8550
> >>
> >> The motivation behind having a separate IRIS driver was discussed earlier in [1]
> >> In the same discussion, it was ellaborated on how the impact would be with
> >> change in the new firmware interface and other video layers in the driver. I can
> >> add this in cover letter in the next revision.
> >
> > Ok. So the changes cover the HFI interface. Is that correct?
> Change wise, yes.
>
> >> We see some duplication of code and to handle the same, the series brings in a
> >> common code reusability between iris and venus. Aligning the common peices of
> >> venus and iris will be a work in progress, once we land the base driver for iris.
> >
> > This is not how it usually works. Especially not with the patches you
> > have posted.
> >
> > I have the following suggestion how this story can continue:
> > You can _start_ by reworking venus driver, separating the HFI /
> > firmware / etc interface to an internal interface in the driver. Then
> > implement Iris as a plug in for that interface. I might be mistaken
> > here, but I think this is the way how this can be beneficial for both
> > the video en/decoding on both old and new platforms.
>
> HFI/firmware interface is already confined to HFI layer in the existing venus
> driver. We explained in the previous discussion [1], on how the HFI change
> impacts the other layers by taking example of a DRC usecase. Please have a look
> considering the usecase and the impact it brings to other layers in the driver.

I have looked at it. And I still see huge change in the interface
side, but it doesn't tell me about the hardware changes.

Have you evaluated the other opportunity?

To have a common platform interface and firmware-specific backend?

You have already done a part of it, but from a different perspective.
You have tried to move common code out of the driver. Instead we are
asking you to do a different thing. Move non-common code within the
driver. Then add your code on top of that.

>
> [1] https://lore.kernel.org/lkml/8c97d866-1cab-0106-4ab3-3ca070945ef7@quicinc.com/
> > Short rationale:
> > The venus driver has a history of supported platforms. There is
> > already some kind of buffer management in place. Both developers and
> > testers have spent their effort on finding issues there. Sending new
> > driver means that we have to spend the same amount of efforts on this.
> > Moreover, even from the porter point of view. You are creating new
> > bindings for the new hardware. Which do not follow the
> > venus-common.yaml. And they do not follow the defined bindings for the
> > recent venus platforms. Which means that as a developer I have to care
> > about two different ways to describe nearly the same hardware.>> Again qualcomm video team does not have a plan to support sm8550/x1e80100 on
> >> venus as the changes are too interleaved to absorb in venus driver. And there is
> >> significant interest in community to start validating video driver on sm8550 or
> >> x1e80100.
> >>
> >> [1] https://lore.kernel.org/lkml/8c97d866-1cab-0106-4ab3-3ca070945ef7@quicinc.com/
> >>
> >> Regards,
> >> Vikash
> >
> >
> >



-- 
With best wishes
Dmitry

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