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From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 3/3] MMC: sdhci-dove: allow GPIOs to be used for card detection on Dove
Date: Fri, 23 Nov 2012 12:55:07 +0000	[thread overview]
Message-ID: <20121123125507.GO5764@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20121123121422.GA26168@S2100-06.ap.freescale.net>

On Fri, Nov 23, 2012 at 08:14:27PM +0800, Shawn Guo wrote:
> On Fri, Nov 23, 2012 at 08:57:26AM +0000, Russell King - ARM Linux wrote:
> > Does this work with the sdhci stuff?
> 
> Honestly, I'm not sure, but I guess it does, since I have seen
> sdhci-pxav3 driver using the helpers.  Anyway, I'm going to adopt
> the helpers for sdhci-esdhc-imx driver to find it out.

The thing that worries me is this:

static void sdhci_tasklet_card(unsigned long param)
{
...
        /* Check host->mrq first in case we are runtime suspended */
        if (host->mrq &&
            !(sdhci_readl(host, SDHCI_PRESENT_STATE) & SDHCI_CARD_PRESENT)) {
                pr_err("%s: Card removed during transfer!\n",
                        mmc_hostname(host->mmc));
                pr_err("%s: Resetting controller.\n",
                        mmc_hostname(host->mmc));

                sdhci_reset(host, SDHCI_RESET_CMD);
                sdhci_reset(host, SDHCI_RESET_DATA);

                host->mrq->cmd->error = -ENOMEDIUM;
                tasklet_schedule(&host->finish_tasklet);
        }
...
        mmc_detect_change(host->mmc, msecs_to_jiffies(200));
}


That gets called whenever a card is inserted/removed by the SDHCI code (if
the SDHCI card detect is wired), or in my case by the interrupt routine
the code in my patch adds.

The slot-gpio.c stuff directly calls into mmc_detect_change (a) with a
shorter delay, and (b) completely omits the above handling and resetting.
My guess from the above code is that it'll work fine 90% of the time
(because you'll remove the card without an active request), but the above
code looks like it's addressing a corner case which will be omitted with
the "generic" slot-gpio.c solution.

So I don't think it's a good idea to use slot-gpio.c in this case.

  reply	other threads:[~2012-11-23 12:55 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-22 23:54 [PATCH 0/3] sdhci-dove GPIO support for card detection Russell King - ARM Linux
2012-11-22 23:55 ` [PATCH 1/3] MMC: sdhci-dove: use devm_clk_get() Russell King
2012-11-22 23:55 ` [PATCH 2/3] MMC: sdhci-dove: use two-stage initialization for sdhci-pltfm Russell King
2012-11-22 23:55 ` [PATCH 3/3] MMC: sdhci-dove: allow GPIOs to be used for card detection on Dove Russell King
2012-11-23  8:31   ` Shawn Guo
2012-11-23  8:57     ` Russell King - ARM Linux
2012-11-23 12:14       ` Shawn Guo
2012-11-23 12:55         ` Russell King - ARM Linux [this message]
2012-11-25 20:29           ` Chris Ball
2012-11-26  9:43             ` Guennadi Liakhovetski
2012-12-03 19:11               ` Chris Ball
2012-12-04 16:00                 ` Guennadi Liakhovetski
2012-12-04 16:06                   ` Chris Ball
2012-12-04 16:43                     ` Russell King - ARM Linux
2012-12-04 18:51                       ` Chris Ball
2012-11-26  6:53   ` Shawn Guo

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