linux-kernel - Re: [PATCH v1] PM-runtime: Check supplier

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Date:   Mon, 27 Jun 2022 16:27:45 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     peter.wang@...iatek.com, Matthias Brugger <matthias.bgg@...il.com>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Avri Altman <avri.altman@....com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>, chun-hung.wu@...iatek.com,
        alice.chao@...iatek.com, cc.chou@...iatek.com,
        chaotian.jing@...iatek.com, jiajie.hao@...iatek.com,
        powen.kao@...iatek.com, qilin.tan@...iatek.com,
        lin.gui@...iatek.com, tun-yu.yu@...iatek.com
Subject: Re: [PATCH v1] PM-runtime: Check supplier_preactivated before release supplier

On Mon, Jun 27, 2022 at 4:14 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Mon, Jun 13, 2022 at 08:07:55PM +0800, peter.wang@...iatek.com wrote:
> > From: Peter Wang <peter.wang@...iatek.com>
> >
> > With divice link of DL_FLAG_PM_RUNTIME, if consumer call pm_runtime_get_suppliers
> > to prevent supplier enter suspend, pm_runtime_release_supplier should
> > check supplier_preactivated before let supplier enter suspend.
> >
> > If the link is drop or release, bypass check supplier_preactivated.
> >
> > Signed-off-by: Peter Wang <peter.wang@...iatek.com>
> > ---
> >  drivers/base/core.c          |  2 +-
> >  drivers/base/power/runtime.c | 15 ++++++++++++---
> >  include/linux/pm_runtime.h   |  5 +++--
> >  3 files changed, 16 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index 7cd789c4985d..3b9cc559928f 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -486,7 +486,7 @@ static void device_link_release_fn(struct work_struct *work)
> >       /* Ensure that all references to the link object have been dropped. */
> >       device_link_synchronize_removal();
> >
> > -     pm_runtime_release_supplier(link, true);
> > +     pm_runtime_release_supplier(link, true, true);
> >
> >       put_device(link->consumer);
> >       put_device(link->supplier);
> > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> > index 676dc72d912d..3c4f425937a1 100644
> > --- a/drivers/base/power/runtime.c
> > +++ b/drivers/base/power/runtime.c
> > @@ -314,10 +314,19 @@ static int rpm_get_suppliers(struct device *dev)
> >   * and if @check_idle is set, check if that device is idle (and so it can be
> >   * suspended).
> >   */
> > -void pm_runtime_release_supplier(struct device_link *link, bool check_idle)
> > +void pm_runtime_release_supplier(struct device_link *link, bool check_idle,
> > +     bool drop)
>
> This is just making this horrible api even worse.  Now there are 2
> boolean flags required, 2 more than really should even be here at all.
> Every time you see this function being used, you will now have to look
> up the definition  to see what it really does.
>
> Please make a new function that calls the internal function with the
> flag set properly, so that it is obvious what is happening when the call
> is made.
>
> and really, the same thing should be done for the check_idle flag,
> that's not good either.

Agreed, and let me take care of this.