linux-kernel - Re: [PATCH V2 1/3] mmc: esdhc: enable polling to detect card by itself

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Message-ID: <509B1CEE.6090306@marvell.com>
Date:	Thu, 08 Nov 2012 10:46:06 +0800
From:	yongd <yongd@...vell.com>
To:	Shawn Guo <shawn.guo@...aro.org>
Cc:	Chris Ball <cjb@...top.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Daniel Drake <dsd@...top.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Wilson Callan <wilson.callan@...antsystems.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Zhangfei Gao <zgao6@...vell.com>,
	Kevin Liu <kliu5@...vell.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 1/3] mmc: esdhc: enable polling to detect card by itself

On 2012年11月06日 20:52, Shawn Guo wrote:
> On Tue, Nov 06, 2012 at 04:49:42PM +0800, yongd wrote:
>>  From your info, we can see that on your platform, those pins (including
>> power, clk, DATA) necessary for MMC_SEND_STATUS transaction still keep
>> connected for some time just after the GPIO's level changes due to card
>> removable. And if we remove the card very slowly, such time duration can be
>> such long that the MMC_SEND_STATUS query can still succeed.
>>
> I was not removing the card as slowly as you think. It's actually
> a normal speed.  That's why I thought your patch breaks the
> card-detection functionality before I found the cause.
>
>> So I think we can add a proper delay(maybe 100ms) before the gpio interrupt
>> triggers the MMC_SEND_STATUS query, and maybe this can probably fix this issue:-)
>>
> I do not think it's a proper fixing.
Anyway, u can try such delay like msleep(100) in cd_irq() before calling
tasklet_schedule(&sdhost->card_tasklet). Yes, this is not a proper fix even
it works:-)
>
> <snip>
>
>> Anyway, I 100% agree with you that for a ESDHC_CD_GPIO card, we shall query gpio
>> state to know such card's presence rather than sending MMC_SEND_STATUS rudely.
>>
>> But just as I mentioned before, I don't think using SDHCI_QUIRK_BROKEN_CARD_DETECTION
>> as the flag to determine whether and how we can know card's presence before sending
>> command is a proper way.
>>
>> I haven't gotten any good idea. Do u have any idea on this?
>>
> I guess what we need is to call mmc_gpio_get_cd() trying to know card's
> presence before sending MMC_SEND_STATUS command.  sdhci-esdhc-imx
> driver will surely need some changes to cope with that.
>
> Shawn
>
Yes, gpio card detection should better use the existing framework 
offered by slot-gpio.
Then the fake-card-present will be unnecessary. BTW, sdhci-s3c.c also 
dose not use slot-gpio,
and then it also adds some tricky logic for gpio detection. U can check 
sdhci_s3c_notify_change(),
which dynamically set/clear SDHCI_QUIRK_BROKEN_CARD_DETECTION. This 
patch adding
mmc_gpio_get_cd(), bec9d4e5939987053169a9bb48fc58b6a2d3e237, mentioned 
this 1stly.

But using SDHCI_QUIRK_BROKEN_CARD_DETECTION to do such judging in 
sdhci_request()
is still not proper. I think this is the root causing such above 
workarounds.

So I am thinking of adding a new operation like get_card_presence into 
sdhci_ops,
and then different host drivers can implement differently by themselves, 
eg, for
sdhci-esdhc-imx.c,

static bool esdhc_get_card_presence(struct sdhci_host *host)
{
bool present = true;

if (detection_type == ESDHC_CD_CONTROLLER)
present = sdhci_readl(host, SDHCI_PRESENT_STATE) & SDHCI_CARD_PRESENT;
else if (detection_type == ESDHC_CD_GPIO) {
if (gpio_get_value(boarddata->cd_gpio))
/* no card, if a valid gpio says so... */
present = false;
}

return present;
}


But this will also cause lots of host drivers corresponding changes. Oh, 
still inconvenient:-(
Any better ideas?

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