linux-kernel - Re: [PATCH v2 2/3] sdhci-pci : Enable runtime PM support

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Message-ID: <AANLkTi=iZ3dzAoRuRdpvQ=uBp4u8O8LtMuu2XdSWeZwr@mail.gmail.com>
Date:	Sun, 13 Feb 2011 11:42:01 +0100
From:	Pierre Tardy <tardyp@...il.com>
To:	Chris Ball <cjb@...top.org>, "Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Pierre Tardy <pierre.tardy@...el.com>,
	linux-pm@...ts.linux-foundation.org, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, Yunpeng Gao <yunpeng.gao@...el.com>
Subject: Re: [PATCH v2 2/3] sdhci-pci : Enable runtime PM support

> On Sun, Feb 06, 2011 at 07:02:49PM +0100, Pierre Tardy wrote:
>> From: Yunpeng Gao <yunpeng.gao@...el.com>
>>
>> Follow the kernel runtime PM framework, enable runtime PM support of the
>> sdhci host controller with pci interface.
>>
>> Note that this patch implements runtime_pm but now actually detects
>> activity.
>> It relies on higher level (childrens) to do actual waking up
>> Activity detection is put in following patch
>
> Testing this patchset in linux-next-20100208 gives:
>
> [   10.829223] sdhci: Secure Digital Host Controller Interface driver
> [   10.829548] sdhci: Copyright(c) Pierre Ossman
> [   10.883906] sdhci-pci 0000:0d:00.0: SDHCI controller found [1180:e822] (rev 1)
> [   10.884533] sdhci-pci 0000:0d:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
> [   10.885189] sdhci-pci 0000:0d:00.0: Will use DMA mode even though HW doesn't fully claim to support it.
> [   10.886176] sdhci-pci 0000:0d:00.0: setting latency timer to 64
> [   10.886819] Registered led device: mmc0::
> [   10.887281] mmc0: SDHCI controller on PCI [0000:0d:00.0] using DMA
> [   10.887724] sdhci-pci 0000:0d:00.0: Unbalanced pm_runtime_enable!
> [   10.888498] sdhci-pci 0000:17:00.0: SDHCI controller found [1180:e822] (rev 1)
> [   10.889179] sdhci-pci 0000:17:00.0: PCI INT A -> GSI 19 (level, low) -> IRQ 19
> [   10.889876] sdhci-pci 0000:17:00.0: Will use DMA mode even though HW doesn't fully claim to support it.
> [   10.890924] sdhci-pci 0000:17:00.0: setting latency timer to 64
> [   10.891387] Registered led device: mmc1::
> [   10.891900] mmc1: SDHCI controller on PCI [0000:17:00.0] using DMA
> [   10.892280] sdhci-pci 0000:17:00.0: Unbalanced pm_runtime_enable!
>
> (Note the last line above.)

I never have seen this before. I'm not testing those patches on
mmc-next, as our platform is not totally upstream yet, and do not boot
on 2.6.37+ based kernel.
However, we backported the pm_runtime patches from 2.6.37. Is there
some differences in very latest patches on default enablement of
runtime_pm?

>
> I then removed the card and reinserted it, but there's no dmesg output
> related to the reinsert, only to the card removal:
>
> [   65.381047] mmc0: card d555 removed
>
> So, card insertion is broken.  I then did rmmod sdhci-pci && modprobe
> sdhci-pci, and it picked up the card again.

So what you have here is non working card-detection when device is in PCI_D3.
This sounds like a HW limitation in you platform.

D3 is originally meant for suspend to ram, so it sounds logic that
some HW wont support wake on card detect.
it sounds like we need a SDHCI_RUNTIME_PM_CAP, so that we can properly
describe which HW can be safely put D3 at runtime.
Also, maybe on some HW, D1 will support wake on card detect. I dont
know how can the driver hint pci subsystem that it should go D1 rather
than D3 in the runtime_pm flow.
Maybe Rafael can advice on this.

Regards,
Pierre
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