linux-kernel - Re: [PATCH v14 4/6] soc: qcom: rpmh: Invoke rpmh

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Message-ID: <CAD=FV=WEH_A4SvyX0uv9Z_n+z9_SYcdm2LfsLRK7qALEiOyHqQ@mail.gmail.com>
Date:   Fri, 27 Mar 2020 11:22:29 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Maulik Shah <mkshah@...eaurora.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Evan Green <evgreen@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Lina Iyer <ilina@...eaurora.org>, lsrao@...eaurora.org
Subject: Re: [PATCH v14 4/6] soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches

Hi,

On Fri, Mar 27, 2020 at 4:00 AM Maulik Shah <mkshah@...eaurora.org> wrote:
>
>   * @ctrlr: controller making request to flush cached data
>   *
> - * Return: -EBUSY if the controller is busy, probably waiting on a response
> - * to a RPMH request sent earlier.
> + * Return: 0 on success, error number otherwise.
>   *
> - * This function is always called from the sleep code from the last CPU
> - * that is powering down the entire system. Since no other RPMH API would be
> - * executing at this time, it is safe to run lockless.
> + * This function can either be called from sleep code on the last CPU
> + * (thus no spinlock needed) or with the ctrlr->cache_lock already held.
>
> Now you can remove the "or with the ctrlr->cache_lock already held"
> since it's no longer true.
>
> It can be true for other RSCs, so i kept as it is.

I don't really understand this.  The cache_lock is only a concept in
"rpmh.c".  How could another RSC grab the cache lock?  If nothing
else, can you remove this comment until support for those other RSCs
are added and we can evaluate then?

-Doug