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

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Message-ID: <20121105124809.GA27260@S2100-06.ap.freescale.net>
Date:	Mon, 5 Nov 2012 20:48:11 +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 Mon, Nov 05, 2012 at 11:34:49AM +0800, yongd wrote:
> From the code logic, without SDHCI_QUIRK_BROKEN_CARD_DETECTION for ESDHC_CD_GPIO, when your card (using
> GPIO detection) is removed, we can know the card's absence through the fake CARD_PRESENT flag in esdhc_readl_le().
> As a result, we can quickly return ENOMEDIUM error without command sending. Finally mmc_rescan can know the card
> is removed.
> 
Yes, that's the existing implementation, which does not require retry
sending MMC_SEND_STATUS to know if card is removed.

> On the other hand, with SDHCI_QUIRK_BROKEN_CARD_DETECTION for ESDHC_CD_GPIO, we will just send MMC_SEND_STATUS
> command (cd_irq->sdhci_tasklet_card->mmc_recan->mmc_sd_detect->mmc_sd_alive), and we will find error since the card
> is already gone. Finally, we shall also know the card is removed.
> 
> This is really strange why the removal message shows up together with the next card inserting message.
> Could u pls tell us more about what actually happened when the card is removed with my patches? Did the GPIO interrupt
> happen? Was mmc_rescan() called? Did mmc_sd_detect() finally find error when it sent MMC_SEND_STATUS? What step did
> the card removing procedure arrive at? Really really thanks a lot:-)
> 
I just tracked it down a little bit.  Interesting enough, it depends on
how I remove the card.  If I do it slowly, when the gpio interrupt
triggers the MMC_SEND_STATUS query, the command can still retrieve
the card status successfully.  Thus driver does not detect the card
removal.  If I remove the card from slot quickly, I can see the removal
message.

With your patch series, in ESDHC_CD_GPIO case the driver will have
to send MMC_SEND_STATUS (with retry) to card for knowing its presence.
This is also an unpleasant behavior comparing to the existing code.
I think we should query gpio state to know card presence for this case.

Shawn

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