Re: [PATCH 0/4] qcom-cpufreq-hw: Add CPU clock provider support

Manivannan Sadhasivam
2022-10-21T08:03:06Z

On Thu, Oct 20, 2022 at 10:52:30AM +0530, Viresh Kumar wrote:
> + Johan,
>
> On 19-10-22, 19:29, Manivannan Sadhasivam wrote:
> > Hello,
> >
> > This series adds clock provider support to the Qcom CPUFreq driver for
> > supplying the clocks to the CPU cores in Qcom SoCs.
> >
> > The Qualcomm platforms making use of CPUFreq HW Engine (EPSS/OSM) supply
> > clocks to the CPU cores. But this is not represented clearly in devicetree.
> > There is no clock coming out of the CPUFreq HW node to the CPU. This created
> > an issue [1] with the OPP core when a recent enhancement series was submitted.
> > Eventhough the issue got fixed in the OPP framework in the meantime, that's
> > not a proper solution and this series aims to fix it properly.
> >
> > There was also an attempt made by Viresh [2] to fix the issue by moving the
> > clocks supplied to the CPUFreq HW node to the CPU. But that was not accepted
> > since those clocks belong to the CPUFreq HW node only.
> >
> > The proposal here is to add clock provider support to the Qcom CPUFreq HW
> > driver to supply clocks to the CPUs that comes out of the EPSS/OSM block.
> > This correctly reflects the hardware implementation.
> >
> > The clock provider is a simple one that just provides the frequency of the
> > clocks supplied to each frequency domain in the SoC using .recalc_rate()
> > callback. The frequency supplied by the driver will be the actual frequency
> > that comes out of the EPSS/OSM block after the DCVS operation. This frequency
> > is not same as what the CPUFreq framework has set but it is the one that gets
> > supplied to the CPUs after throttling by LMh.
> >
> > This series has been tested on SM8450 based dev board and hence there is a DTS
> > change only for that platform. Once this series gets accepted, rest of the
> > platform DTS can also be modified and finally the hack on the OPP core can be
> > dropped.
>
> Thanks for working on this Mani.
>
> Can you also test the below code over your series ? This shouldn't
> result in issues that Johan reported earlier [1][2]. Below is the hack I
> am carrying in the OPP core for Qcom SoCs at the moment.
>
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index e87567dbe99f..b7158d33c13d 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1384,20 +1384,6 @@ static struct opp_table *_update_opp_table_clk(struct device *dev,
> }
>
> if (ret == -ENOENT) {
> - /*
> - * There are few platforms which don't want the OPP core to
> - * manage device's clock settings. In such cases neither the
> - * platform provides the clks explicitly to us, nor the DT
> - * contains a valid clk entry. The OPP nodes in DT may still
> - * contain "opp-hz" property though, which we need to parse and
> - * allow the platform to find an OPP based on freq later on.
> - *
> - * This is a simple solution to take care of such corner cases,
> - * i.e. make the clk_count 1, which lets us allocate space for
> - * frequency in opp->rates and also parse the entries in DT.
> - */
> - opp_table->clk_count = 1;
> -
> dev_dbg(dev, "%s: Couldn't find clock: %d\n", __func__, ret);
> return opp_table;
> }
> diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c
> index 96a30a032c5f..402c507edac7 100644
> --- a/drivers/opp/debugfs.c
> +++ b/drivers/opp/debugfs.c
> @@ -138,7 +138,7 @@ void opp_debug_create_one(struct dev_pm_opp *opp, struct opp_table *opp_table)
> * - For some devices rate isn't available or there are multiple, use
> * index instead for them.
> */
> - if (likely(opp_table->clk_count == 1 && opp->rates[0]))
> + if (likely(opp_table->clk_count == 1))
> id = opp->rates[0];
> else
> id = _get_opp_count(opp_table);
>

With the above diffs applied, I no longer see the issues reported by Johan on
SM8450 dev board.

Thanks,
Mani

> --
> viresh
>
> [1] https://lore.kernel.org/all/YsxSkswzsqgMOc0l@hovoldconsulting.com/
> [2] https://lore.kernel.org/all/Ys2FZa6YDwt7d%2FZc@hovoldconsulting.com/

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