[PATCH 11/17] drm/msm: Add support for IFPC

[Konrad Dybcio]

On 7/22/25 11:27 PM, Akhil P Oommen wrote:
> On 7/22/2025 7:19 PM, Dmitry Baryshkov wrote:
>> On Sun, Jul 20, 2025 at 05:46:12PM +0530, Akhil P Oommen wrote:
>>> Add a new quirk to denote IFPC (Inter-Frame Power Collapse) support
>>> for a gpu. Based on this flag send the feature ctrl hfi message to
>>> GMU to enable IFPC support.
>>>
>>> Signed-off-by: Akhil P Oommen <akhilpo at oss.qualcomm.com>
>>> ---

[...]

>>> +static int a6xx_hfi_enable_ifpc(struct a6xx_gmu *gmu)
>>> +{
>>> +	if (gmu->idle_level != GMU_IDLE_STATE_IFPC)
>>> +		return 0;
>>> +
>>> +	return a6xx_hfi_feature_ctrl_msg(gmu, HFI_FEATURE_IFPC, 1, 0x1680);
>>
>> magic number?
>>
> 
> Let me check.

techpack-graphics/adreno_a6xx_gmu.c:
537:#define A6X_GMU_LONG_IFPC_HYST      FIELD_PREP(GENMASK(15, 0), 0x1680)
541:#define A6X_GMU_LONG_IFPC_HYST_FLOOR        FIELD_PREP(GENMASK(15, 0), 0x0F00)

(same value for a7/a8)

0x0f00 is 3840, which smells oddly like the XO clock rate (possibly mul/div2)

(38.4 MHz or 19.2) / 3840 is (1000 or 500) (ms? us? cycles?) and the other one is
(333 or 667) - without any further information I'd estimate this is some sort of
scheduler tuning

Konrad