linux-kernel - Re: [PATCH v10 03/11] drm/etnaviv: Add dedicated functions to create and destroy platform device

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Message-ID: <ab17a1e6-c621-9a92-73fc-8b762fd0800e@loongson.cn>
Date:   Wed, 21 Jun 2023 22:35:24 +0800
From:   Sui Jingfeng <suijingfeng@...ngson.cn>
To:     Lucas Stach <l.stach@...gutronix.de>,
        Sui Jingfeng <18949883232@....com>,
        Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Philipp Zabel <p.zabel@...gutronix.de>,
        etnaviv@...ts.freedesktop.org
Subject: Re: [PATCH v10 03/11] drm/etnaviv: Add dedicated functions to create
 and destroy platform device

Hi,

On 2023/6/21 22:00, Lucas Stach wrote:
> Am Mittwoch, dem 21.06.2023 um 21:31 +0800 schrieb Sui Jingfeng:
>> On 2023/6/21 18:23, Lucas Stach wrote:
>>>> While back to the question you ask, I want etnaviv_create_platform_device() to be generic,
>>>>
>>>> can be used by multiple place for multiple purpose.
>>>>
>>>> I have successfully copy this to a another drm driver by simply renaming.
>>>>
>>>> The body of the function itself does not need to change.
>>> But it isn't shared,
>> This can be shared for drm/etnaviv in the future,
>>
>> currently, we just need an opportunity to use this function.
>>
> I'm not convinced, yet.
>
>> I want to create a dummy platform device,
>>
>> let this dummy platform be bound to the single PCI GPU master.
>>
>>
>> etnaviv_create_platform_device("dummy", &dummy_device);
>>
>>
>> 1) To verify the component code path on PCI case.
>>
> My favorite option would be to just always use the component path even
> when the GPU is on a PCI device to keep both paths mostly aligned. One
> could easily image both a 3D and a 2D core being made available though
> the same PCI device.

Component is for something that is possible not available. (or something 
is optional)

Yes it provided flexibly, but don't forget, it rely on the DT.


But for the PCIe device, it always the case that all of the hardware is 
available at the same time

when the device driver(kernel module) is loaded.


>> 2) Possibly for create a device for some other tiny hardware logic
>> come with the platform
>>
> Do you have something in mind here? Until now I assumed that only the
> GPU core is behind the PCI abstraction. Is there something else sharing
> the MMIO space?

A display controller, HDMI phy, vga encoder etc


I have a discrete PCIe GPU card from another vendor,

It integrated display controller and vivante GPU and unknown VPUs.

All of the  hardware block mentioned above sharing the MMIO space.

There are available on the same time when you mount this discrete PCIe 
GPU card on the mother board

>
> Regards,
> Lucas
>
>> 3) Revival component_compare_dev_name() function.
>>
>>> in this compilation unit this function is specific
>>> to the etnaviv driver and I don't see why we shouldn't have etnaviv
>>> specifics in there if it makes the code of this driver easier to
>>> follow.

-- 
Jingfeng