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

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Date:	Tue, 16 Oct 2012 21:01:40 -0700
From:	Yong Ding <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>, Jialing Fu <jlfu@...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 1/3] mmc: esdhc: enable polling to detect card by itself

Shawn,
Thanks for your comment. And sorry for my so late due to illness:-)
SDHCI_QUIRK_BROKEN_CARD_DETECTION is used for notifying we don't use the host internal card detection method so that we don't need enable/disable those relevant interrupt bits of host(sdhci_set_card_detection in sdhci.c). 
And as I double-checked the latest kernel code, actually sdhci-esdhc-imx sets this flag by default, and then will clear it only when the detection type is ESDHC_CD_CONTROLLER. So this aligns with my understanding. 
What I want to do is that 1st we shall set MMC_CAP_NEEDS_POLL by our host driver itself and 2nd remove the improper logic in sdhci_add_host() . How do u think? Thanks.

________________________________________
From: Shawn Guo [shawn.guo@...aro.org]
Sent: Sunday, October 07, 2012 22:06
To: Yong Ding
Cc: Chris Ball; Anton Vorontsov; Marek Szyprowski; Wolfram Sang; Daniel Drake; Sascha Hauer; Wilson Callan; Ben Dooks; Zhangfei Gao; Kevin Liu; Jialing Fu; linux-mmc@...r.kernel.org; linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mmc: esdhc: enable polling to detect card by itself

On Fri, Sep 28, 2012 at 06:28:31PM +0800, yongd wrote:
> In the current code logic, sdhci_add_host() will enable the polling
> method (set MMC_CAP_NEEDS_POLL) for a removable card (MMC_CAP_
> NONREMOVABLE is not set) whose host's internal card detection method
> is disabled for some reason (SDHCI_QUIRK_BROKEN_CARD_DETECTION is set).
>
> However, this is improper since we can have some other card detection
> methods besides host internal card detection and polling method. For
> example, if the card detection type is ESDHC_CD_GPIO (external gpio pin
> for CD), we will keep SDHCI_QUIRK_BROKEN_CARD_DETECTION set. This is right.
> But, just as above said, sdhci_add_host() will also enable polling for such
> a card. This is redundant.
>
At least for sdhci-esdhc-imx, SDHCI_QUIRK_BROKEN_CARD_DETECTION will
be set only when neither ESDHC_CD_GPIO nor ESDHC_CD_CONTROLLER works.

Shawn

> On the other hand, for the card with ESDHC_CD_NONE detection type(no CD, neither
> controller nor gpio, so use polling), we currently rely on sdhci_add_host() to
> enable polling for us.
>
> Here proposed a solution for such an embarrassing case. 1st, this patch will
> de-couple polling enabling with sdhci_add_host() by doing this in host driver
> itself, just as some other vendors. 2nd, one more patch will remove such improper
> MMC_CAP_NEEDS_POLL enabling in sdhci_add_host().
>
> Change-Id: Ia7525009d8fd188e3f0169f225e4a76ff9e94b47
> Signed-off-by: yongd <yongd@...vell.com>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c |    1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index e23f813..f70079c 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -569,6 +569,7 @@ static int __devinit sdhci_esdhc_imx_probe(struct platform_device *pdev)
>               break;
>
>       case ESDHC_CD_NONE:
> +             host->mmc->caps = MMC_CAP_NEEDS_POLL;
>               break;
>       }
>
> --
> 1.7.9.5
>
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