Re: [PATCH V2 06/15] cpufreq: mediatek: Record previous target vproc value

Rex-BC Chen
2022-04-11T11:35:15Z

On Fri, 2022-04-08 at 15:36 +0200, AngeloGioacchino Del Regno wrote:
> Il 08/04/22 06:58, Rex-BC Chen ha scritto:
> > From: Jia-Wei Chang <jia-wei.chang@mediatek.com>
> >
> > We found the buck voltage may not be exactly the same with what we
> > set
> > because CPU may share the same buck with other module.
> > Therefore, we need to record the previous desired value instead of
> > reading
> > it from regulators.
> >
> > Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
> > Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.com>
> > ---
> > drivers/cpufreq/mediatek-cpufreq.c | 31 +++++++++++++++++++----
> > -------
> > 1 file changed, 20 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/cpufreq/mediatek-cpufreq.c
> > b/drivers/cpufreq/mediatek-cpufreq.c
> > index dc4a87e68940..472f4de29e5f 100644
> > --- a/drivers/cpufreq/mediatek-cpufreq.c
> > +++ b/drivers/cpufreq/mediatek-cpufreq.c
> > @@ -40,6 +40,7 @@ struct mtk_cpu_dvfs_info {
> > struct list_head list_head;
> > int intermediate_voltage;
> > bool need_voltage_tracking;
> > + int old_vproc;
> > };
> >
> > static LIST_HEAD(dvfs_info_list);
> > @@ -190,11 +191,17 @@ static int
> > mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
> >
> > static int mtk_cpufreq_set_voltage(struct mtk_cpu_dvfs_info
> > *info, int vproc)
> > {
> > + int ret;
> > +
> > if (info->need_voltage_tracking)
> > - return mtk_cpufreq_voltage_tracking(info, vproc);
> > + ret = mtk_cpufreq_voltage_tracking(info, vproc);
> > else
> > - return regulator_set_voltage(info->proc_reg, vproc,
> > - vproc + VOLT_TOL);
> > + ret = regulator_set_voltage(info->proc_reg, vproc,
> > + MAX_VOLT_LIMIT);
> > + if (!ret)
> > + info->old_vproc = vproc;
> > +
> > + return ret;
> > }
> >
> > static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
> > @@ -211,15 +218,7 @@ static int mtk_cpufreq_set_target(struct
> > cpufreq_policy *policy,
> >
> > inter_vproc = info->intermediate_voltage;
> >
> > - old_freq_hz = clk_get_rate(cpu_clk);
> > - old_vproc = regulator_get_voltage(info->proc_reg);
> > - if (old_vproc < 0) {
> > - pr_err("%s: invalid Vproc value: %d\n", __func__,
> > old_vproc);
> > - return old_vproc;
> > - }
> > -
> > freq_hz = freq_table[index].frequency * 1000;
> > -
> > opp = dev_pm_opp_find_freq_ceil(cpu_dev, &freq_hz);
> > if (IS_ERR(opp)) {
> > pr_err("cpu%d: failed to find OPP for %ld\n",
> > @@ -229,6 +228,16 @@ static int mtk_cpufreq_set_target(struct
> > cpufreq_policy *policy,
> > vproc = dev_pm_opp_get_voltage(opp);
> > dev_pm_opp_put(opp);
> >
> > + old_freq_hz = clk_get_rate(cpu_clk);
> > + old_vproc = info->old_vproc;
> > + if (old_vproc == 0)
> > + old_vproc = regulator_get_voltage(info->proc_reg);
> > + if (old_vproc < 0) {
> > + dev_err(cpu_dev, "%s: invalid Vproc value: %d\n",
> > + __func__, old_vproc);
> > + return old_vproc;
> > + }
>
> From my understandment, if this fails once, it fails forever!
>
> info->old_vproc is set only if info->need_voltage_tracking is true,
> and only
> in mtk_cpufreq_set_voltage(): this function is called only after the
> checks
> that you've introduced there, and that's on previously stored values.
> While this was fine in the previous version, because it was always
> calling
> regulator_get_voltage(), here it's not.
>
> I think that a good option here is to:
>
> old_vproc = info->old_vproc;
> if (old_vproc <= 0)
> old_vproc = regulator_get_voltage(info->proc_reg);
> if (old_vproc < 0) {
> dev_err and return
> }
>
> ...or, if this is not applicable, we should still find another way to
> not
> let this driver to simply fail forever in case anything goes wrong.
>
> Regards,
> Angelo

Hello Angelo,

Yes, your concern is right.
I will add this in next version.

if (old_vproc <= 0)
old_vproc = regulator_get_voltage(info->proc_reg);
if (old_vproc < 0) {
dev_err and return
}

BRs,
Rex