Re: [PATCH] mmc: dw_mmc: fix dw_mci_get_cd

[zhangfei <zhangfei.gao@linaro.org>]

On 01/16/2014 12:22 AM, Russell King - ARM Linux wrote:

> Well, having this in the gpio level as well as in subsystems like MMC
> is going to create confusion - and from the results of this patch _IS_
> causing confusion.  You've just encouraged one implementation to have
> things setup such that mmc_gpio_get_cd() returns false when a card is
> inserted, rather than it correctly returning true.
>
> The issue here is that we'll potentially now end up with _three_
> inversions.  One in the GPIO layers.  One in mmc_gpio_get_cd(), and
> another in every driver which uses the GPIO layer inversion.  This
> is hardly the right approach as it leads to multiple points where
> confusion about the inverted status can occur.
>

Thanks Russell, make sense.

Double checked with the hardware guy, cd pin is high when card inserted 
on the board.
The cd pin is originally connected to vout via a resister, and 
internally short to gound, which is broken when card inserted.

Then Optional properties "caps2-mmc-cd-active-high" has to be added.

--- a/Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt
+++ b/Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt

+* caps2-mmc-cd-active-high: cd pin is high when card present

@@ -2411,6 +2414,9 @@ static struct dw_mci_board *dw_mci_parse_dt(struct 
dw_mci *host)
         if (of_find_property(np, "caps2-mmc-hs200-1_2v", NULL))
                 pdata->caps2 |= MMC_CAP2_HS200_1_2V_SDR;

+       if (of_find_property(np, "caps2-mmc-cd-active-high", NULL))
+               pdata->caps2 |= MMC_CAP2_CD_ACTIVE_HIGH;
+

Thanks