linux-kernel - Re: [PATCH 2/2] clk: qcom: gdsc: Add support for set_hwmode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ZLUhRlm20xlZ3OJj@linaro.org>
Date:   Mon, 17 Jul 2023 14:08:54 +0300
From:   Abel Vesa <abel.vesa@...aro.org>
To:     Taniya Das <quic_tdas@...cinc.com>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        avel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Taniya Das <tdas@....qualcomm.com>, linux-pm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] clk: qcom: gdsc: Add support for set_hwmode_dev

On 23-07-10 09:40:14, Taniya Das wrote:
> Hi Abel,
> 
> Thanks for the patch.
> 
> On 6/28/2023 10:48 PM, Konrad Dybcio wrote:
> > On 28.06.2023 12:56, Abel Vesa wrote:
> > > Implement the GDSC specific genpd set_hwmode_dev callback in order to
> > > switch the HW control on or off. For any GDSC that supports HW control
> > > set this callback in order to allow its consumers to control it.
> > > 
> > > Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> > > ---
> > This still does nothing to prevent the HW_CTRL state being changed in
> > init, enable and disable functions.
> > 
> > Konrad
> > >   drivers/clk/qcom/gdsc.c | 22 ++++++++++++++++++++++
> > >   1 file changed, 22 insertions(+)
> > > 
> > > diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> > > index 5358e28122ab..9a04bf2e4379 100644
> > > --- a/drivers/clk/qcom/gdsc.c
> > > +++ b/drivers/clk/qcom/gdsc.c
> > > @@ -314,6 +314,26 @@ static int gdsc_enable(struct generic_pm_domain *domain)
> > >   	return 0;
> > >   }
> > > +static int gdsc_set_hwmode_dev(struct generic_pm_domain *domain,
> > > +			       struct device *dev, bool enable)
> > > +{
> > > +	int ret = gdsc_hwctrl(domain_to_gdsc(domain), enable);
> > > +
> > > +	if (ret)
> > > +		goto out;
> > > +
> > > +	/*
> > > +	 * Wait for the GDSC to go through a power down and
> > > +	 * up cycle.  In case there is a status polling going on
> > > +	 * before the power cycle is completed it might read an
> > > +	 * wrong status value.
> > > +	 */
> > > +	udelay(1);
> > > +
> > > +out:
> > > +	return ret;
> > > +}
> > > +
> > >   static int gdsc_disable(struct generic_pm_domain *domain)
> > >   {
> > >   	struct gdsc *sc = domain_to_gdsc(domain);
> > > @@ -451,6 +471,8 @@ static int gdsc_init(struct gdsc *sc)
> > >   		sc->pd.power_off = gdsc_disable;
> > >   	if (!sc->pd.power_on)
> > >   		sc->pd.power_on = gdsc_enable;
> > > +	if (sc->flags & HW_CTRL)
> > > +		sc->pd.set_hwmode_dev = gdsc_set_hwmode_dev;
> We do not want to move to SW mode without consumers wanting to move to this
> mode.
> 
> We want a new flag for the consumers wanting to move to this mode. The mode
> in which the GDSC would be enabled would be in SW mode only.
> +	if (sc->flags & HW_CTRL_TRIGGER) {
> +		sc->pd.set_hwmode_dev = gdsc_set_mode;
> +	}
> +

OK, maybe I'm missing something here.

Do you suggest we have GDSCs that, even though they support HW ctrl,
should not be controllable by the consumer?

Why isn't dev_pm_genpd_set_hwmode good enough? If a consumer doesn't
want to control it then the consumer can just skip calling the mentioned
function.

Or maybe you want this all hidden into the genpd provider?

> 
> > >   	ret = pm_genpd_init(&sc->pd, NULL, !on);
> > >   	if (ret)
> 
> -- 
> Thanks & Regards,
> Taniya Das.