Re: [PATCH v5 2/4] soc: qcom: ice: Add OPP-based clock scaling support for ICE

[Abhinaba Rakshit <abhinaba.rakshit@oss.qualcomm.com>]

On Thu, Feb 12, 2026 at 12:30:00PM +0100, Konrad Dybcio wrote:
> On 2/11/26 10:47 AM, Abhinaba Rakshit wrote:
> > Register optional operation-points-v2 table for ICE device
> > and aquire its minimum and maximum frequency during ICE
> > device probe.
> > 
> > Introduce clock scaling API qcom_ice_scale_clk which scale ICE
> > core clock based on the target frequency provided and if a valid
> > OPP-table is registered. Use flags (if provided) to decide on
> > the rounding of the clock freq against OPP-table. Incase no flags
> > are provided use default behaviour (CEIL incase of scale_up and FLOOR
> > incase of ~scale_up). Disable clock scaling if OPP-table is not
> > registered.
> > 
> > When an ICE-device specific OPP table is available, use the PM OPP
> > framework to manage frequency scaling and maintain proper power-domain
> > constraints.
> > 
> > Also, ensure to drop the votes in suspend to prevent power/thermal
> > retention. Subsequently restore the frequency in resume from
> > core_clk_freq which stores the last ICE core clock operating frequency.
> > 
> > Signed-off-by: Abhinaba Rakshit <abhinaba.rakshit@oss.qualcomm.com>
> > ---
> 
> [...]
> 
> > +/**
> > + * qcom_ice_scale_clk() - Scale ICE clock for DVFS-aware operations
> > + * @ice: ICE driver data
> > + * @target_freq: requested frequency in Hz
> > + * @scale_up: If @flags is 0, choose ceil (true) or floor (false)
> > + * @flags: Rounding policy (ICE_CLOCK_ROUND_*); overrides @scale_up
> > + *
> > + * Clamps @target_freq to the OPP range (min/max), selects an OPP per rounding
> > + * policy, then applies it via dev_pm_opp_set_rate() (including voltage/PD
> > + * changes).
> > + *
> > + * Return: 0 on success; -EOPNOTSUPP if no OPP table; or error from
> > + *         dev_pm_opp_set_rate()/OPP lookup.
> > + */
> > +int qcom_ice_scale_clk(struct qcom_ice *ice, unsigned long target_freq,
> > +		       bool scale_up, unsigned int flags)
> > +{
> > +	int ret;
> > +	unsigned long ice_freq = target_freq;
> > +	struct dev_pm_opp *opp;
> 
> Reverse-Christmas-tree ordering would be neat

Ack, will update.

> 
> > +
> > +	if (!ice->has_opp)
> > +		return -EOPNOTSUPP;
> > +
> > +	/* Clamp the freq to max if target_freq is beyond supported frequencies */
> > +	if (ice->max_freq && target_freq >= ice->max_freq) {
> > +		ice_freq = ice->max_freq;
> > +		goto scale_clock;
> > +	}
> > +
> > +	/* Clamp the freq to min if target_freq is below supported frequencies */
> > +	if (ice->min_freq && target_freq <= ice->min_freq) {
> > +		ice_freq = ice->min_freq;
> > +		goto scale_clock;
> > +	}
> 
> The OPP framework won't let you overclock the ICE if this is what these checks
> are about. Plus the clk framework will perform rounding for you too

Right, maybe I can just add a check for 0 freq just to ensure the export API is
not miss used.
Something shown below:

if (!target_freq)
    return -EINVAL;

However, my main concern was for the corner cases, where:
(target_freq > max && ROUND_CEIL)
and
(target_freq < min && ROUND_FLOOR)
In both the cases, the OPP APIs will fail and the clock remains unchanged.
Hence, I added the checks to make the API as generic/robust as possible.

Please let me know, your thoughts.

> > +
> > +	switch (flags) {
> 
> Are you going to use these flags? Currently they're dead code

I agree, currently they are not used.
However, since its an export API, I want to keep the rounding FLAGS
support as it a common to have rounding flags in clock scaling APIs,
and to support any future use-cases as well.

> > +	case ICE_CLOCK_ROUND_CEIL:
> > +		opp = dev_pm_opp_find_freq_ceil_indexed(ice->dev, &ice_freq, 0);
> 
You never use the index (hardcoded to 0)

Ack, will update.

> 
> > +		break;
> > +	case ICE_CLOCK_ROUND_FLOOR:
> > +		opp = dev_pm_opp_find_freq_floor_indexed(ice->dev, &ice_freq, 0);
> > +		break;
> > +	default:
> > +		if (scale_up)
> > +			opp = dev_pm_opp_find_freq_ceil_indexed(ice->dev, &ice_freq, 0);
> > +		else
> > +			opp = dev_pm_opp_find_freq_floor_indexed(ice->dev, &ice_freq, 0);
> 
> Is this distinction necessary?

Well not necessary. However, I wanted to have the scale_up option as well and make use of
it in the API. Hence, I thought of having this to be harmless.

> Konrad