[PATCH 1/2] drm/amd/pm/si: Check AMD_IS_MOBILITY flag for PPSMC_SYSTEMFLAG_GPIO_DC

[<contact@mikaelpelle.com>]

I tested this patch on a Late 2013 Mac Pro (MacPro6,1) with dual Apple FirePro D700 (Tahiti XT, 6 GB), and can confirm that it fixes the DPM issue on the D700 as well.

Test environment:
Arch Linux
Kernel: 6.18.54-1-lts + this patch
Mesa/RADV: 26.2.3
GPU: 2x FirePro D700 (Tahiti XT, 6 GB)
Params: radeon.si_support=0 amdgpu.si_support=1

Without the patch, both D700s remained at 300 MHz SCLK / 150 MHz MCLK under Vulkan compute load.
I checked the D700 VBIOS as well: ATOM_PP_PLATFORM_CAP_HARDWAREDC is set, and it contains a battery state at 300/150 MHz.
With the patch applied to the same kernel, each D700 correctly transitions from 300/150 MHz at idle to 850/1370 MHz under load. I tested both GPUs individually and simultaneously.
As a real-world test, Ollama/Qwen3-8B fully offloaded across both GPUs sustained approximately 18.3-18.7 tokens/s, compared with ~2.34 tokens/s before the patch. One API run generated 1517 tokens in 81.24 seconds.   
I observed no amdgpu VM faults, GPU timeouts or resets during the tests.
Tested-by: Mikael Pelle contact@mikaelpelle.com