Re: [PATCH] mmc: mxs: fix card detection function for broken card detect
From: Ulf Hansson
Date: Mon Apr 28 2014 - 05:31:20 EST
On 28 April 2014 11:13, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote:
> On Sat, Apr 19, 2014 at 11:59:18PM +0200, Daniel Willmann wrote:
>> Return -ENOSYS in get_cd if broken-cd is specified in the device tree.
>>
>> Commit a91fe279ae75 (mmc: mxs: use standard flag for broken card
>> detection) sets MMC_CAP_NEEDS_POLL when broken-cd is specified. This
>> driver sets this flag unconditionally as it does not support a card
>> detect interrupt. Instead, broken-cd means that there is no card detect
>> signal connected.
>>
>> The mmc core checks the get_cd function return value to determine if a
>> card is present. Only for a non-zero return value it will attempt to
>> initialize the card. So retuning -ENOSYS will allow the card to be
>> initialized.
>> For comparison, mmc_gpio_get_cd in slot-gpio.c also returns -ENOSYS if
>> the card detect GPIO is not valid.
>
> Short answer for fixing this regression:
>
> Acked-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
>
> Long answer:
>
> This is broken in the MMC OF parser. When the parser finds the
> 'broken-cd' property it just sets the MMC_CAP_NEEDS_POLL flag. This is
> wrong. broken-cd means that we cannot rely on any card detection, but
> instead have to talk to the card to find out if it's available.
> Currently there is no flag to signal this situation, so the host driver
> has to handle this by returning true in the get_cd callback, just like
> the patch below does.
>
> IMO the correct solution would be to add a MMC_CAP_CD_NEEDS_TALK_TO_CARD
> flag to the core.
>
So if I understand correct, you want the host-ops->get_cd function to
be invoked from the mmc rescan - only when it actually can provide
useful information?
Kind regards
Ulf Hansson
> Sascha
>
>>
>> Signed-off-by: Daniel Willmann <daniel@xxxxxxxxxxxxxxxxxxxx>
>> ---
>> This might be relevant for stable kernels. The patch was tested with 3.14.1 on
>> olinuxino nano.
>>
>> drivers/mmc/host/mxs-mmc.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c
>> index 073e871a0fc8..babfea03ba8a 100644
>> --- a/drivers/mmc/host/mxs-mmc.c
>> +++ b/drivers/mmc/host/mxs-mmc.c
>> @@ -70,6 +70,7 @@ struct mxs_mmc_host {
>> unsigned char bus_width;
>> spinlock_t lock;
>> int sdio_irq_en;
>> + bool broken_cd;
>> };
>>
>> static int mxs_mmc_get_cd(struct mmc_host *mmc)
>> @@ -78,6 +79,9 @@ static int mxs_mmc_get_cd(struct mmc_host *mmc)
>> struct mxs_ssp *ssp = &host->ssp;
>> int present, ret;
>>
>> + if (host->broken_cd)
>> + return -ENOSYS;
>> +
>> ret = mmc_gpio_get_cd(mmc);
>> if (ret >= 0)
>> return ret;
>> @@ -568,6 +572,7 @@ static int mxs_mmc_probe(struct platform_device *pdev)
>> {
>> const struct of_device_id *of_id =
>> of_match_device(mxs_mmc_dt_ids, &pdev->dev);
>> + struct device_node *np = pdev->dev.of_node;
>> struct mxs_mmc_host *host;
>> struct mmc_host *mmc;
>> struct resource *iores;
>> @@ -634,6 +639,8 @@ static int mxs_mmc_probe(struct platform_device *pdev)
>> mmc->caps = MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED |
>> MMC_CAP_SDIO_IRQ | MMC_CAP_NEEDS_POLL;
>>
>> + host->broken_cd = of_property_read_bool(np, "broken-cd");
>> +
>> mmc->f_min = 400000;
>> mmc->f_max = 288000000;
>>
>> --
>> 1.8.4.2
>>
>>
>
> --
> Pengutronix e.K. | |
> Industrial Linux Solutions | http://www.pengutronix.de/ |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
> Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/