[PATCH] mmc: dt: Add 'broken-cd' DT binding

[Chris Ball]

Hi,

On Tue, Aug 21 2012, Rob Herring wrote:
>> cd-gpios and cd-external can be present on the same node.  if broken-cd
>> is present, it must be the only one of these nodes used.
>
> I don't see the point of cd-external. Either you just use the CD
> interrupt defined within the SDHCI or you have a gpio line independent
> of the SDHCI and use cd-gpios.

You've described two of the possible cases, but not the third.  In the
third case, you have a gpio line that is not independent of the SDHCI,
because it is the SDHCI's CD pin brought out to be directly accessible
via a GPIO.

The difference is in the handling of the interrupt -- if you don't have
"cd-external" then you're just using the SDHCI's interrupt, but if you
have an independent line then you're going to need to register your own
IRQ handler on it, and "cd-external" signifies that.

Thomas wrote this explanation earlier in the thread:
> "samsung,sdhci-cd-gpio" means that the cd-gpio line is not connected
> to the card-detect pad of the sdhci controller. Instead, it identifies
> cd-gpio as a gpio pin, connected to the card-detect pin of the "card
> slot" and it can used as a source of external interrupt. The driver
> can register card insert/remove handler for this interrupt and get
> notified about the changes in card state.
> 
> "sdhci-cd-internal" means that the "cd-gpio" line is used to connect
> the card-detect pin of the card slot and the card-detect pad of the
> sdhci controller. The controller is then aware of any changes in card
> state and the controller generates appropriate interrupts to notify
> changes in card-state.

Thanks,

- Chris.
-- 
Chris Ball   <cjb at laptop.org>   <http://printf.net/>
One Laptop Per Child