linux-kernel - Re: [RFC PATCH] mmc: sdhci-of-at91: don't put device in suspend after probe

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Date:	Wed, 10 Feb 2016 15:16:24 +0100
From:	Ludovic Desroches <ludovic.desroches@...el.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
CC:	<nicolas.ferre@...el.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	<ulf.hansson@...aro.org>, <linux-mmc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] mmc: sdhci-of-at91: don't put device in suspend
 after probe

On Wed, Feb 10, 2016 at 03:00:09PM +0200, Adrian Hunter wrote:
> On 10/02/16 14:51, Ludovic Desroches wrote:
> > Hi Adrian,
> > 
> > On Wed, Feb 10, 2016 at 01:50:44PM +0200, Adrian Hunter wrote:
> >> On 10/02/16 11:58, Ludovic Desroches wrote:
> >>> By putting the device in suspend at the end of the probe, it is
> >>> impossible to wake up on non software event such as card
> >>> insertion/removal.
> >>>
> >>> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
> >>> ---
> >>>
> >>> Hi,
> >>>
> >>> Since I had no feedback on this topic:
> >>> http://permalink.gmane.org/gmane.linux.kernel.mmc/35160
> >>>
> >>> I would like to no more put the device in suspend at the end of the probe. If
> >>> my device is suspended at the end of the probe, I have no issue to resume on
> >>> a software event such as mounting my sdcard but hardware event such as card
> >>> insertion and removal do not trigger a resume.
> >>
> >> You can't use runtime PM unless you have a way to wake-up.
> >>
> > 
> > Thanks for your feedback. I am a bit disappointed since Ulf advised me to use
> > runtime PM instead of system PM.
> > 
> >> Currently, sdhci disables card detect interrupts when runtime suspended,
> >> and drivers use a card-detect GPIO to wake-up.
> >>
> > 
> > It is what I have seen going through the sdhci layer. So next question is:
> > is it normal to not take care of card detect interrupts? We keep enabled
> > some IRQs probably for SDIO modules IRQ but not for card detection. I
> > don't understand the reason.
> 
> Does sdhci-of-at91.c generate card detect interrupts while runtime suspended?

It could if I keep one or two clocks enabled (need extra tests to be
sure about the clock needed to get this interrupt). I have tried to modify
quickly sdhci_runtime_suspend_host() to enable card insertion/removal,
there is an irq generated but the kernel complains this irq is not
handled. I didn't dig further, it was only to do a simple test.

> 
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