drm/loongson: Error out if no VRAM detected

[Katyusha]

Hi,

On 2024/1/21 5:28, Sui JIngfeng wrote:
> Hi,
>
>
> On 2024/1/20 20:01, Katyusha wrote:
>>
>> Hi,
>>
>> This patch works fine with my Loongson 3A5000M laptop (L71), which 
>> has a 7A1000 chipset without VRAM.
>>
>>
>
> Can you give more details about the hardware configuration about this 
> laptop?
> For example, by using 'lspci | grep VGA' command. I want to make sure 
> if the
> integrated display controller are there.
>
>
> Normally, the integrated graphics should not be used if there is no 
> dedicated
> VRAM equipped. And the platform BIOS should disable it.
>
Here's my result of lspci:

$ sudo lspci -k | grep VGA
00:06.1 VGA compatible controller: Loongson Technology LLC DC (Display 
Controller) (rev 01)
07:00.0 VGA compatible controller: Advanced Micro Devices, Inc. 
[AMD/ATI] Oland [Radeon HD 8570 / R5 430 OEM / R7 240/340 / Radeon 520 
OEM] (rev 87)