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

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Message-ID: <20121106125253.GC27643@S2100-06.ap.freescale.net>
Date:	Tue, 6 Nov 2012 20:52:54 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	yongd <yongd@...vell.com>
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 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.

<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

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