Message-ID: <6224223ec1ead769f281af54f93bd3142a8e212b.camel@mediatek.com>
Date:   Tue, 24 Aug 2021 18:21:48 +0800
From:   "yunfei.dong@...iatek.com" <yunfei.dong@...iatek.com>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
CC:     Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        "Tzung-Bi Shih" <tzungbi@...omium.org>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomasz Figa <tfiga@...gle.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fritz Koenig <frkoenig@...omium.org>,
        Irui Wang <irui.wang@...iatek.com>,
        linux-media <linux-media@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        George Sun <george.sun@...iatek.com>
Subject: Re: [PATCH v5, 00/15] Using component framework to support multi
 hardware decode

Hi Ezequiel,

Thanks for your suggestion.

On Sun, 2021-08-22 at 11:32 -0300, Ezequiel Garcia wrote:
> On Fri, 20 Aug 2021 at 04:59, yunfei.dong@...iatek.com
> <yunfei.dong@...iatek.com> wrote:
> > 
> > Hi Ezequiel,
> > 
> > Thanks for your detail feedback.
> > 
> > On Thu, 2021-08-19 at 11:10 -0300, Ezequiel Garcia wrote:
> > > On Thu, 19 Aug 2021 at 04:13, yunfei.dong@...iatek.com
> > > <yunfei.dong@...iatek.com> wrote:
> > > > 
> > > > Hi Ezequiel,
> > > > 
> > > > Thanks for your suggestion.
> > > > 
> > > > On Wed, 2021-08-18 at 11:11 -0300, Ezequiel Garcia wrote:
> > > > > +danvet
> > > > > 
> > > > > Hi,
> > > > > 
> > > > > On Tue, 10 Aug 2021 at 23:58, Yunfei Dong <
> > > > > yunfei.dong@...iatek.com>
> > > > > wrote:
> > > > > > 
> > > > > > This series adds support for multi hardware decode into
> > > > > > mtk-vcodec,
> > > > > > by first
> > > > > > adding component framework to manage each hardware
> > > > > > information:
> > > > > > interrupt,
> > > > > > clock, register bases and power. Secondly add core thread
> > > > > > to deal
> > > > > > with core
> > > > > > hardware message, at the same time, add msg queue for
> > > > > > different
> > > > > > hardware
> > > > > > share messages. Lastly, the architecture of different specs
> > > > > > are not
> > > > > > the same,
> > > > > > using specs type to separate them.
> > > > > > 
> > > > > 
> > > > > I don't think it's a good idea to introduce the component API
> > > > > in the
> > > > > media subsystem. It doesn't seem to be maintained, IRC
> > > > > there's not
> > > > > even
> > > > > a maintainer for it, and it has some issues that were never
> > > > > addressed.
> > > > > 
> > > > > It would be really important to avoid it. Is it really needed
> > > > > in the
> > > > > first place?
> > > > > 
> > > > > Thanks,
> > > > > Ezequiel
> > > > 
> > > > For there are many hardware need to use, mt8192 is three and
> > > > mt8195 is
> > > > five. Maybe need more to be used in the feature.
> > > > 
> > > > Each hardware has independent clk/power/iommu port/irq.
> > > > Use component interface in prob to get each component's
> > > > information.
> > > > Just enable the hardware when need to use it, very convenient
> > > > and
> > > > simple.
> > > > 
> > > > I found that there are many modules use component to manage
> > > > hardware
> > > > information, such as iommu and drm etc.
> > > > 
> > > 
> > > Many drivers support multiple hardware variants, where each
> > > variant
> > > has a different number of clocks or interrupts, see for instance
> > > struct hantro_variant which allows to expose different codec
> > > cores,
> > > some having both decoder/encoder, and some having just a decoder.
> > > 
> > > The component API is mostly used by DRM to aggregate independent
> > > subdevices (called components) into an aggregated driver.
> > > 
> > > For instance, a DRM driver needs to glue together the HDMI, MIPI,
> > > and plany controller, or any other hardware arrangement where
> > > devices can be described independently.
> > > 
> > 
> > The usage scenario is very similar with drm and iommu, So decide to
> > use
> > component framework.
> > Decode has three/five or more hardwares, these hardware are
> > independent.
> > For mt8183 just need core hardware to decode, but mt8192 has
> > lat,soc and
> > core hardware to decode. When lat need to use, just enable lat
> > hardware,
> > core is the same.And mt8195 will has two cores, each core can work
> > well
> > independent.
> > 
> > For each component device just used to open their power/clk/iommu
> > port/irq when master need to enable it. The main logic is in master
> > device.
> > 
> > > The component API may look simple but has some issues, it's not
> > > easy
> > > to debug, and can cause troubles if not used as expected [1].
> > > It's worth making sure you actually need a framework
> > > to glue different devices together.
> > > 
> > 
> > Each hardware has its index, master can get hardware information
> > according these index, looks not complex. What do you mean about
> > not
> > easy to debug?
> > 
> > > > Do you have any other suggestion for this architecture?
> > > > 
> > > 
> > > Looking at the different patchsets that are posted, it's not
> > > clear
> > > to me what exactly are the different architectures that you
> > > intend
> > > to support, can you some documentation which clarifies that?
> > > 
> > 
> > Have five hardwares lat,soc,core0,core1 and main. Lat thread can
> > use lat
> > soc and main, core thread can use soc,lat, core0 and core1. Core
> > thread
> > can be used or not for different project.
> 
> Can you explain what are these lat,soc and core threads for?
> 
You can regards lat,soc and core as hardware, each hardware can work
independent. Lat and core threads used to control hardware to decode.
> > Also Need to use these
> > hardware dynamic at the same time. So I use component framework,
> > just
> > need to know the used  hardware index according to different
> > project.Need not to do complex logic to manage these hardwares.
> > 
> 
> I am not thrilled to see the component framework introduced to the
> media subsystem. Like I said, it has no clear maintainer, and it's
> not
> easy to use.
> 
How do you think about Deniel Vetter's mail ? It looks that there are
maintainer for it.
> The media subsystem has some support which AFAIK does the same thing,
> see v4l2-async, which is maintained by media people.
> 
If component can be used, I prefer to use it. At the other hand, I will
try to use these method as compared.
> Please push a branch based on media/master containing these changes.
> I see there are other patch series for this device, but it's hard to
> track
> which goes first, etc.
> 
I need time to push a branch, or you can get the latest kernel and git
am these patches, maybe much quicker.
> Thanks,
> Ezequiel

Thanks,
Yunfei Dong

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