From: Ludovic Desroches <ludovic.desroches@atmel.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-mmc <linux-mmc@vger.kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Nicolas Ferre <nicolas.ferre@atmel.com>,
<linux-pm@vger.kernel.org>, <rjw@rjwysocki.net>,
<khilman@kernel.org>
Subject: Re: [PATCH] mmc: sdhci-of-at91: fix wakeup issue when using runtime pm
Date: Wed, 9 Mar 2016 17:38:09 +0100 [thread overview]
Message-ID: <20160309163809.GM2690@odux.rfo.atmel.com> (raw)
In-Reply-To: <CAPDyKFpDHooacBrTXQzinO4U10SeoedybN5HZ5y1bwbO-F04ug@mail.gmail.com>
+ PM mailing list since the discussion is mixing PM and sdhci
On Tue, Mar 08, 2016 at 10:56:31PM +0100, Ulf Hansson wrote:
> +Ludovic
>
> On 8 March 2016 at 22:54, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> > On 4 March 2016 at 14:48, Ludovic Desroches <ludovic.desroches@atmel.com> wrote:
[snip]
> >>
> >> Coming back to the initial discussion and patch which were motivated by
> >> the fact that after runtime suspend I can't wake-up on card detect event,
> >> I have the feeling we don't have the same assumption about runtime PM.
> >>
> >> From what you and Adrian told me, I should not use runtime PM if I have
> >> no way to wake-up. In your minds, the way to wake-up is to use an
> >> externel GPIO because the controller will be 'totally' disabled, isn't it?
> >
> > I agree to the first part here.
> >
> > Although, as you also have the option to use polling for card detect,
> > this actually means you don't really *need* to have a wakeup
> > configured. Especially in the case where you don't have GPIO card
> > detect.
> >
> > In that way, *all* the clocks can gated in between the polling
> > attempts, thus you will save power even in the polling mode
> > configuration and when runtime PM is enabled.
> >
As you said, I can gate all the clocks but only between attempts.
Regularly, I will resume and suspend my controller to perform the card
detection. I don't know if it is a better solution than keeping one
clock enabled and waiting for an interrupt to enable the other ones.
> >>
> >> On my side, runtime PM allows me to save power when the sdhci controller
> >> is not used. If I can disable two clocks out of three, I should use
> >> runtime PM. Do you agree?
> >>
> >> If not, tell me how I can convince you :) Otherwise, next step is to rework
> >> my patch but I think I have no other solution that not calling
> >> sdhci_runtime_suspend_host if I expect to use the card detect irq of the
> >> controller.
> >
> > So, to summarize.
> >
> > I think the best fix is to add a clever check in ->probe() and then
> > enable polling when you can't rely on GPIO card detect IRQ.
> >
> > Moreover, to have a robust solution, you also need to clear
> > SDHCI_QUIRK_BROKEN_CARD_DETECTION for your sdhci variant, as otherwise
> > the "broken-cd" DT binding could wrongly be used for this variant.
> >
> > Does that make sense?
Well I don't agree totally because I have the feeling to use a
workaround because if sdhci_runtime_suspend_host has been called the
controlled is considered as 'disabled' then we won't deal with its IRQs.
I would like to move forward on this issue so it could be a trade-off.
Since the sdhci layer is going to be reworked, maybe it could be
interesting to have another approach of runtime PM to get more
flexibility.
Regards
Ludovic
next prev parent reply other threads:[~2016-03-09 16:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-11 13:48 [PATCH] mmc: sdhci-of-at91: fix card detect when using runtime PM Ludovic Desroches
2016-02-11 15:10 ` Ulf Hansson
2016-02-12 8:38 ` Ludovic Desroches
2016-02-12 11:01 ` Ulf Hansson
2016-02-12 12:04 ` Ludovic Desroches
2016-02-13 9:56 ` [PATCH] mmc: sdhci-of-at91: fix wakeup issue when using runtime pm Ludovic Desroches
2016-02-16 14:38 ` Ulf Hansson
2016-02-16 15:22 ` Ludovic Desroches
2016-02-17 10:35 ` Ludovic Desroches
2016-03-04 9:09 ` Ulf Hansson
2016-03-04 9:12 ` Ulf Hansson
2016-03-04 13:48 ` Ludovic Desroches
2016-03-08 21:54 ` Ulf Hansson
2016-03-08 21:56 ` Ulf Hansson
2016-03-09 16:38 ` Ludovic Desroches [this message]
2016-03-10 10:30 ` Ludovic Desroches
2016-03-11 15:55 ` Ludovic Desroches
2016-03-16 11:04 ` Ulf Hansson
2016-02-25 9:49 ` Ludovic Desroches
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