[Linux-stm32] [PATCH] ARM: dts: stm32: Consistently enable internal pull-ups for SD bus

[Yann GAUTIER]

On 10/14/20 3:30 PM, Marek Vasut wrote:
> On 10/14/20 3:26 PM, Yann GAUTIER wrote:
> [...]
>>> diff --git a/arch/arm/boot/dts/stm32mp15-pinctrl.dtsi b/arch/arm/boot/dts/stm32mp15-pinctrl.dtsi
>>> index b2d19583450c..73d9a5b7f5ba 100644
>>> --- a/arch/arm/boot/dts/stm32mp15-pinctrl.dtsi
>>> +++ b/arch/arm/boot/dts/stm32mp15-pinctrl.dtsi
>>> @@ -1291,13 +1291,13 @@ pins1 {
>>>    				 <STM32_PINMUX('D', 2, AF12)>; /* SDMMC1_CMD */
>>>    			slew-rate = <1>;
>>>    			drive-push-pull;
>>> -			bias-disable;
>>> +			bias-pull-up;
>> Hi Marek,
> 
> Hi,
> 
>> This pin config is used by ST board, where we have a level shifter.
>> This shouldn't be changed. We discussed this with Alex, and a new group
>> should be added in this case.
> 
> Is it a problem if we enable the pulls up unconditionally with the level
> shifter present, to make the properties of the SD bus consistent ?
> 
The risk of having 2 parallel pull-ups is that the resulting value could 
be below the lower acceptable value for SD. I'll check if that can occur.


Yann
>>>    		};
>>>    		pins2 {
>>>    			pinmux = <STM32_PINMUX('C', 12, AF12)>; /* SDMMC1_CK */
>>>    			slew-rate = <2>;
>>>    			drive-push-pull;
>>> -			bias-disable;
>>> +			bias-pull-up;
>> Same case for this one.
>>>    		};
>>>    	};
> 
> [...]
>