On 22/01/16 14:07, Ulf Hansson wrote:
> On 22 January 2016 at 10:45, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>> In the future sdhci will be a library. When that happens
>> a callback will be needed to allow drivers easily to override
>> the standard way of determining whether a card is present.
>
> There's already a ->get_cd() callback in the struct mmc_host_ops.
>
> By turning sdhci into a library, each sdhci variant should decide
> whether they want to use a default "sdhci_get_cd()" version, rely on
> slot-gpio or implement their own.
>
> I don't understand why we need a specific sdhci callback to deal with
> this, it doesn't make sense to me.
>
>> That is needed because functions like sdhci_request() also
>> check the card presence.
>
> Why does sdhci do that? Is that because some variants needs it or
> because of all?
There has been a check for card present in the request function since the
driver was added in 2006. On our host controllers, and I presume others, if
a command is started when the host controller has decided there is no card,
then nothing happens. No interrupts, no errors, it just sits there.
The driver has a 10-second timer that eventually catches it.
So that is the reason for checking the Present State register. When GPIO
support was added, people just decided to substitute the check.
>
> Reading a state of a GPIO pin before every request doesn't come
> without a cost in performance. My point is, it should only be done
> when *really* needed.
> Again, by having sdhci to become a library each variant should decide
> what's needed for them.
Sure but this is a bug fix, ideally for stable. It can't deal with
unrelated improvements.
>
>>
>> The get_cd callback is being added now to facilitate
>> a bug fix, for which subsequent patches are provided.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx # v4.4+
>> ---
>> drivers/mmc/host/sdhci.c | 6 +++++-
>> drivers/mmc/host/sdhci.h | 1 +
>> 2 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index d622435d1bcc..535236084b27 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -1612,7 +1612,7 @@ static void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>>
>> static int sdhci_do_get_cd(struct sdhci_host *host)
>> {
>> - int gpio_cd = mmc_gpio_get_cd(host->mmc);
>> + int gpio_cd;
>>
>> if (host->flags & SDHCI_DEVICE_DEAD)
>> return 0;
>> @@ -1621,10 +1621,14 @@ static int sdhci_do_get_cd(struct sdhci_host *host)
>> if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
>> return 1;
>>
>> + if (host->ops->get_cd)
>> + return host->ops->get_cd(host);
>> +
>> /*
>> * Try slot gpio detect, if defined it take precedence
>> * over build in controller functionality
>> */
>> + gpio_cd = mmc_gpio_get_cd(host->mmc);
>> if (!IS_ERR_VALUE(gpio_cd))
>> return !!gpio_cd;
>>
>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
>> index 7654ae5d2b4e..a6c2cd8ef0b2 100644
>> --- a/drivers/mmc/host/sdhci.h
>> +++ b/drivers/mmc/host/sdhci.h
>> @@ -552,6 +552,7 @@ struct sdhci_ops {
>> struct mmc_card *card,
>> unsigned int max_dtr, int host_drv,
>> int card_drv, int *drv_type);
>> + int (*get_cd)(struct sdhci_host *host);
>> };
>>
>> #ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS
>> --
>> 1.9.1
>>
>
> Can you please try to fix this without adding a new callback!? I know,
> it requires some more efforts but for sure it's doable.
This is a bug fix for v4.4+ so there is limited scope for major changes.
Could do the change below and replace the other get_cd. Thoughts?
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index ba4f5a0a7b06..e7dd4c82c5f1 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1301,7 +1301,7 @@ static void sdhci_request(struct mmc_host *mmc, struct
mmc_request *mrq)
sdhci_runtime_pm_get(host);
/* Firstly check card presence */
- present = sdhci_do_get_cd(host);
+ present = mmc->ops->get_cd(mmc);
spin_lock_irqsave(&host->lock, flags);
--
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