[PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[Tianrui Zhao]

LoongArch systems with hybrid graphics (integrated +
discrete GPU) can benefit from the same GPU switching
mechanism that x86 laptops use. Relax the dependency
to allow VGA_SWITCHEROO to be built on LoongArch,
consistent with the existing dependencies on ACPI,
PCI, and FB=y.

Change-Id: I84d38fdfe5e1591495fb3681474a7f1f64281fa8
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
---
 drivers/gpu/vga/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
index bad4bcee313..89edd1211aa 100644
--- a/drivers/gpu/vga/Kconfig
+++ b/drivers/gpu/vga/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 config VGA_SWITCHEROO
 	bool "Laptop Hybrid Graphics - GPU switching support"
-	depends on X86
+	depends on X86 || LOONGARCH
 	depends on ACPI
 	depends on PCI
 	depends on FB=y
-- 
2.39.1

Re: [PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[Thomas Zimmermann]

Hi

Am 29.10.26 um 02:36 schrieb Tianrui Zhao:
> LoongArch systems with hybrid graphics (integrated +
> discrete GPU) can benefit from the same GPU switching
> mechanism that x86 laptops use. Relax the dependency
> to allow VGA_SWITCHEROO to be built on LoongArch,
> consistent with the existing dependencies on ACPI,
> PCI, and FB=y.
>
> Change-Id: I84d38fdfe5e1591495fb3681474a7f1f64281fa8

Internal change ids should be remove before submitting patches.

> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
> ---
>   drivers/gpu/vga/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
> index bad4bcee313..89edd1211aa 100644
> --- a/drivers/gpu/vga/Kconfig
> +++ b/drivers/gpu/vga/Kconfig
> @@ -1,7 +1,7 @@
>   # SPDX-License-Identifier: GPL-2.0-only
>   config VGA_SWITCHEROO
>   	bool "Laptop Hybrid Graphics - GPU switching support"
> -	depends on X86
> +	depends on X86 || LOONGARCH

I'm a bit skeptical if that's all there is to do.  Does loongarch really 
work with the existing handlers in the graphics drivers as-is?  See [1] 
for the interface that implements the actual switching.

[1] 
https://elixir.bootlin.com/linux/v7.3/source/include/linux/vga_switcheroo.h#L93

Best regards
Thomas

>   	depends on ACPI
>   	depends on PCI
>   	depends on FB=y

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)

Re: [PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[zhaotianrui]

在 2026/10/29 下午4:16, Thomas Zimmermann 写道:
> Hi
>
> Am 29.10.26 um 02:36 schrieb Tianrui Zhao:
>> LoongArch systems with hybrid graphics (integrated +
>> discrete GPU) can benefit from the same GPU switching
>> mechanism that x86 laptops use. Relax the dependency
>> to allow VGA_SWITCHEROO to be built on LoongArch,
>> consistent with the existing dependencies on ACPI,
>> PCI, and FB=y.
>>
>> Change-Id: I84d38fdfe5e1591495fb3681474a7f1f64281fa8
>
> Internal change ids should be remove before submitting patches.
>
Thanks for your review, I will fix this.


Best regards

Tianrui Zhao

>> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
>> ---
>>   drivers/gpu/vga/Kconfig | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
>> index bad4bcee313..89edd1211aa 100644
>> --- a/drivers/gpu/vga/Kconfig
>> +++ b/drivers/gpu/vga/Kconfig
>> @@ -1,7 +1,7 @@
>>   # SPDX-License-Identifier: GPL-2.0-only
>>   config VGA_SWITCHEROO
>>       bool "Laptop Hybrid Graphics - GPU switching support"
>> -    depends on X86
>> +    depends on X86 || LOONGARCH
>
> I'm a bit skeptical if that's all there is to do.  Does loongarch 
> really work with the existing handlers in the graphics drivers as-is?  
> See [1] for the interface that implements the actual switching.
>
> [1] 
> https://elixir.bootlin.com/linux/v7.3/source/include/linux/vga_switcheroo.h#L93
>
> Best regards
> Thomas
>
Thanks,  I will carefully check whether all these vga_switcheroo_handler 
callbacks are supported on the LoongArch platform.


Best regards

Tianrui Zhao

>>       depends on ACPI
>>       depends on PCI
>>       depends on FB=y
>

Re: [PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[Thomas Zimmermann]

Hi

Am 30.10.26 um 08:04 schrieb zhaotianrui:
>
> 在 2026/10/29 下午4:16, Thomas Zimmermann 写道:
>> Hi
>>
>> Am 29.10.26 um 02:36 schrieb Tianrui Zhao:
>>> LoongArch systems with hybrid graphics (integrated +
>>> discrete GPU) can benefit from the same GPU switching
>>> mechanism that x86 laptops use. Relax the dependency
>>> to allow VGA_SWITCHEROO to be built on LoongArch,
>>> consistent with the existing dependencies on ACPI,
>>> PCI, and FB=y.
>>>
>>> Change-Id: I84d38fdfe5e1591495fb3681474a7f1f64281fa8
>>
>> Internal change ids should be remove before submitting patches.
>>
> Thanks for your review, I will fix this.
>
>
> Best regards
>
> Tianrui Zhao
>
>>> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
>>> ---
>>>   drivers/gpu/vga/Kconfig | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
>>> index bad4bcee313..89edd1211aa 100644
>>> --- a/drivers/gpu/vga/Kconfig
>>> +++ b/drivers/gpu/vga/Kconfig
>>> @@ -1,7 +1,7 @@
>>>   # SPDX-License-Identifier: GPL-2.0-only
>>>   config VGA_SWITCHEROO
>>>       bool "Laptop Hybrid Graphics - GPU switching support"
>>> -    depends on X86
>>> +    depends on X86 || LOONGARCH
>>
>> I'm a bit skeptical if that's all there is to do.  Does loongarch 
>> really work with the existing handlers in the graphics drivers 
>> as-is?  See [1] for the interface that implements the actual switching.
>>
>> [1] 
>> https://elixir.bootlin.com/linux/v7.3/source/include/linux/vga_switcheroo.h#L93
>>
>> Best regards
>> Thomas
>>
> Thanks,  I will carefully check whether all these 
> vga_switcheroo_handler callbacks are supported on the LoongArch platform.

Switcheroo used to be required for x86 notebooks from ~2010. Those 
systems had two graphics cards, but only one set of output connectors. 
That design is become rare, I think.

So I'm a bit surprised to see it come back. Which loongarch systems are 
there?

Best regards
Thomas


>
>
> Best regards
>
> Tianrui Zhao
>
>>>       depends on ACPI
>>>       depends on PCI
>>>       depends on FB=y
>>
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)

Re: [PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[zhaotianrui]

在 2026/10/30 下午4:17, Thomas Zimmermann 写道:
> Hi
>
> Am 30.10.26 um 08:04 schrieb zhaotianrui:
>>
>> 在 2026/10/29 下午4:16, Thomas Zimmermann 写道:
>>> Hi
>>>
>>> Am 29.10.26 um 02:36 schrieb Tianrui Zhao:
>>>> LoongArch systems with hybrid graphics (integrated +
>>>> discrete GPU) can benefit from the same GPU switching
>>>> mechanism that x86 laptops use. Relax the dependency
>>>> to allow VGA_SWITCHEROO to be built on LoongArch,
>>>> consistent with the existing dependencies on ACPI,
>>>> PCI, and FB=y.
>>>>
>>>> Change-Id: I84d38fdfe5e1591495fb3681474a7f1f64281fa8
>>>
>>> Internal change ids should be remove before submitting patches.
>>>
>> Thanks for your review, I will fix this.
>>
>>
>> Best regards
>>
>> Tianrui Zhao
>>
>>>> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
>>>> ---
>>>>   drivers/gpu/vga/Kconfig | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
>>>> index bad4bcee313..89edd1211aa 100644
>>>> --- a/drivers/gpu/vga/Kconfig
>>>> +++ b/drivers/gpu/vga/Kconfig
>>>> @@ -1,7 +1,7 @@
>>>>   # SPDX-License-Identifier: GPL-2.0-only
>>>>   config VGA_SWITCHEROO
>>>>       bool "Laptop Hybrid Graphics - GPU switching support"
>>>> -    depends on X86
>>>> +    depends on X86 || LOONGARCH
>>>
>>> I'm a bit skeptical if that's all there is to do.  Does loongarch 
>>> really work with the existing handlers in the graphics drivers 
>>> as-is?  See [1] for the interface that implements the actual switching.
>>>
>>> [1] 
>>> https://elixir.bootlin.com/linux/v7.3/source/include/linux/vga_switcheroo.h#L93
>>>
>>> Best regards
>>> Thomas
>>>
>> Thanks,  I will carefully check whether all these 
>> vga_switcheroo_handler callbacks are supported on the LoongArch 
>> platform.
>
> Switcheroo used to be required for x86 notebooks from ~2010. Those 
> systems had two graphics cards, but only one set of output connectors. 
> That design is become rare, I think.
>
> So I'm a bit surprised to see it come back. Which loongarch systems 
> are there?
>
> Best regards
> Thomas
>
>
Hi Thomas,

Thanks for your reply.

On the Loongson platform, we don't have the "two GPUs but only one set 
of display outputs" scenario you described. However, we do have systems 
where an integrated GPU and a discrete GPU coexist.
We would like to use the vga_switcheroo interface to switch between the 
discrete GPU (DIS) and the integrated GPU (IGD), and to configure the 
default VGA device.
Would this approach be feasible? Do you have any suggestions or 
recommendations?

Best regards
Tianrui Zhao
>>
>>
>> Best regards
>>
>> Tianrui Zhao
>>
>>>>       depends on ACPI
>>>>       depends on PCI
>>>>       depends on FB=y
>>>
>>
>

Re: [PATCH] vga-switcheroo: Allow VGA_SWITCHEROO to be enabled on LoongArch

[Thomas Zimmermann]

Hi

Am 30.10.26 um 09:39 schrieb zhaotianrui:
>
> 在 2026/10/30 下午4:17, Thomas Zimmermann 写道:
>> Hi
>>
>> Am 30.10.26 um 08:04 schrieb zhaotianrui:
>>>
>>> 在 2026/10/29 下午4:16, Thomas Zimmermann 写道:
>>>> Hi
>>>>
>>>> Am 29.10.26 um 02:36 schrieb Tianrui Zhao:
>>>>> LoongArch systems with hybrid graphics (integrated +
>>>>> discrete GPU) can benefit from the same GPU switching
>>>>> mechanism that x86 laptops use. Relax the dependency
>>>>> to allow VGA_SWITCHEROO to be built on LoongArch,
>>>>> consistent with the existing dependencies on ACPI,
>>>>> PCI, and FB=y.
>>>>>
>>>>> Change-Id: I84d38fdfe5e1591495fb3681474a7f1f64281fa8
>>>>
>>>> Internal change ids should be remove before submitting patches.
>>>>
>>> Thanks for your review, I will fix this.
>>>
>>>
>>> Best regards
>>>
>>> Tianrui Zhao
>>>
>>>>> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
>>>>> ---
>>>>>   drivers/gpu/vga/Kconfig | 2 +-
>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/gpu/vga/Kconfig b/drivers/gpu/vga/Kconfig
>>>>> index bad4bcee313..89edd1211aa 100644
>>>>> --- a/drivers/gpu/vga/Kconfig
>>>>> +++ b/drivers/gpu/vga/Kconfig
>>>>> @@ -1,7 +1,7 @@
>>>>>   # SPDX-License-Identifier: GPL-2.0-only
>>>>>   config VGA_SWITCHEROO
>>>>>       bool "Laptop Hybrid Graphics - GPU switching support"
>>>>> -    depends on X86
>>>>> +    depends on X86 || LOONGARCH
>>>>
>>>> I'm a bit skeptical if that's all there is to do.  Does loongarch 
>>>> really work with the existing handlers in the graphics drivers 
>>>> as-is?  See [1] for the interface that implements the actual 
>>>> switching.
>>>>
>>>> [1] 
>>>> https://elixir.bootlin.com/linux/v7.3/source/include/linux/vga_switcheroo.h#L93
>>>>
>>>> Best regards
>>>> Thomas
>>>>
>>> Thanks,  I will carefully check whether all these 
>>> vga_switcheroo_handler callbacks are supported on the LoongArch 
>>> platform.
>>
>> Switcheroo used to be required for x86 notebooks from ~2010. Those 
>> systems had two graphics cards, but only one set of output 
>> connectors. That design is become rare, I think.
>>
>> So I'm a bit surprised to see it come back. Which loongarch systems 
>> are there?
>>
>> Best regards
>> Thomas
>>
>>
> Hi Thomas,
>
> Thanks for your reply.
>
> On the Loongson platform, we don't have the "two GPUs but only one set 
> of display outputs" scenario you described. However, we do have 
> systems where an integrated GPU and a discrete GPU coexist.
> We would like to use the vga_switcheroo interface to switch between 
> the discrete GPU (DIS) and the integrated GPU (IGD), and to configure 
> the default VGA device.
> Would this approach be feasible? Do you have any suggestions or 
> recommendations?

Oh, that's not what vga_switcheroo is for. For your scenario, simply 
provide a DRM driver for each GPU. Selection of the boot-up display 
happens in the UEFI/BIOS.  Picking the correct display hardware at 
runtime is left to clients in user space (or fbcon). DRM itself has not 
preference.

Best regards
Thomas

>
> Best regards
> Tianrui Zhao
>>>
>>>
>>> Best regards
>>>
>>> Tianrui Zhao
>>>
>>>>>       depends on ACPI
>>>>>       depends on PCI
>>>>>       depends on FB=y
>>>>
>>>
>>
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)