Re: [PATCH 3/3] MMC: sdhci-dove: allow GPIOs to be used for card detection on Dove

Russell King - ARM Linux
2012-11-23T12:55:43Z

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.