Re: [PATCH 1/3] ARM: dts: rk3288 Tinker Board (S) sdcard changes

[Robin Murphy <robin.murphy@arm.com>]

Hi David,

On 2019-02-17 12:15 pm, David Summers wrote:
> This patch makes some minor changes to how the sd card is
> described in the device tree for the ASUS Tinker Board (S). In
> particular on the Tinker Board S, when booted from the eMMC, and with
> no card in the sd slot, and the log has endless messages about not
> being able to detect the card.
> 
> Several methods to remove this error have been tried, the only one
> that works is the broken-cd and so that is what is applied here.

I don't have a Tinker Board, but the symptom sounds instantly familiar 
from hacking on another RK3288 box; have you tried adding 
"regulator-always-on" to the vccio_sd regulator?

With the reference design (which I would assume the Tinker Board has no 
reason to deviate from in this area), the CD pin is either wired 
directly to the SoC with no external pull-up, or explicitly pulled up to 
VCCIO_SD. Either way, when the dwmmc driver probes and discovers there 
is no card present, it sets the currently-unnecessary vqmmc-supply as 
inactive, and thus the regulator core turns off VCCIO_SD entirely. 
Unfortunately, this removes the voltage from the entire I/O domain 
including the internal pull-up, which ends up leaving the CD pin 
floating and generating spurious events.

Robin.

> Alas the ASUS schematic is not clear enough to indicate if the card
> detect is wired up to the cpu, the schematic does not show internal
> wiring on the Tinker Board!
> 
> Now this error didn't show up on the Tinker Board, as that machine
> only boots where there is a sd card installed. However as the TB and
> TBS are so similar it is expected that the Tinker Board also doesn't
> have a functioning card detect. Hence the change here is made to the
> dtsi file, so it applies to both TB and TBS.
> 
> The disable-wp is also removed, it doesnt seem needed on the micro
> sdcard slots, and without thisn the card can still be written
> to. Hence this flag is also removed.
> 
> Signed-off-by: David Summers <beagleboard@davidjohnsummers.uk>
> ---
>   arch/arm/boot/dts/rk3288-tinker.dtsi | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/rk3288-tinker.dtsi b/arch/arm/boot/dts/rk3288-tinker.dtsi
> index 2b38075a2917..fceaeed44e34 100644
> --- a/arch/arm/boot/dts/rk3288-tinker.dtsi
> +++ b/arch/arm/boot/dts/rk3288-tinker.dtsi
> @@ -432,9 +432,7 @@
>   	bus-width = <4>;
>   	cap-mmc-highspeed;
>   	cap-sd-highspeed;
> -	card-detect-delay = <200>;
> -	disable-wp;			/* wp not hooked up */
> +	broken-cd;
>   	pinctrl-names = "default";
>   	pinctrl-0 = <&sdmmc_clk &sdmmc_cmd &sdmmc_cd &sdmmc_bus4>;
>   	status = "okay";
>