Re: [PATCH 2/2] vgaswitchreoo: set audio client id in vgaswitchreoo enable function

[jimqu <jimqu-5C7GfCeVMHo@public.gmane.org>]

在 2018/7/16 22:02, Lukas Wunner 写道:
> On Sat, Jul 14, 2018 at 02:15:24PM +0800, jimqu wrote:
>> ??? 2018/7/13 17:27, Lukas Wunner ??????:
>>> On Fri, Jul 13, 2018 at 04:06:02PM +0800, Jim Qu wrote:
>>>> On modern laptop, there are more and more platforms
>>>> have two GPUs, and each of them maybe have audio codec
>>>> for HDMP/DP output. For some dGPU which is no output,
>>>> audio codec usually is disabled.
>>>>
>>>> In currect HDA audio driver, it will set all codec as
>>>> VGA_SWITCHEROO_DIS, the audio which is binded to UMA
>>>> will be suspended if user use debugfs to contorl power
>>>>
>>>> In HDA driver side, it is difficult to know which GPU
>>>> the audio has binded to. So set the bound gpu pci dev
>>>> to vgaswitchroo, the correct audio id will be set in
>>>> vgaswitchreoo enable function.
>>>>
>>>> Signed-off-by: Jim Qu <Jim.Qu@amd.com>
>>> The approach you've taken in this patch won't work if the HDA controller
>>> is bound to a driver after both GPUs have already been bound to a driver
>>> and the handler has already been registered.
>>>
>>> That's because vga_switcheroo_enable() is run when two GPUs have registered
>>> as clients and the handler has also registered.  If the HDA controller is
>>> probed afterwards, its ID will be stuck at VGA_SWITCHEROO_UNKNOWN_ID.
>> In genernic speaking, there are two cases , a. audio client is the third
>> client. b. audio client is not the third client.
>>
>> if audio is third client. vga_switcheroo_ready() is true,
>> vga_switcheroo_enable() can be called in audio client register fuction.
>> if audio is not the third client, vga_switcheroo_enable() will be called in
>> the second GFX client register.
>> In vga_switcheroo_enable() , the first list loop will set two GPU clients'
>> id, and the second list loop will select audio client, set id by its bound
>> gpu pci dev.
> No, if audio is the third client, vga_switcheroo_ready() is *not* true
> because vgasr_priv.active is true.  This is set to true once the two
> GPUs and the handler have registered.  If the audio device registers
> afterwards, vga_switcheroo_enable() will already have been called.
> It's never called twice because it sets vgasr_priv.active = true.
>
> As a result, the audio device is stuck at VGA_SWITCHEROO_UNKNOWN_ID.

Indeed, I almost ignore the vgasr_priv.active, since I added amdgpu to 
blacklist, audio is always the first client. :).
not so bad, Let me rework the patch tomorrow.

Thanks
JimQu

> Thanks,
>
> Lukas

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