Re: [PATCH 4/4] ARM: dts: Fix-up EMMC2 controller's frequency

[Stefan Wahren]

Hi Nicolas,

Am 09.04.21 um 12:54 schrieb Nicolas Saenz Julienne:
> Hi again,
>
> On Wed, 2021-04-07 at 16:37 -0400, Alan Cooper wrote:
>> Nicolas,
>>
>> I got a better description of the failure and it looks like the bus
>> clock needs to be limited to 300KHz for a 500MHz core clock.
>> What's happening is that an internal reset sequence is needed after a
>> command timeout and the reset signal needs to be asserted for at least
>> 2 ticks of the bus clock. This is done using a 12 bit counter clocked
>> by the core clock. That means a 500MHz core clock produces a 122KHz
>> reset signal which is too fast for 2 ticks of the 200KHz bus clock
>> (100KHz) but is okay for the 300KHz (150Khz) bus clock.
> Is there any value in implementing this in a generic way?

i don't have any idea which callback could manipulate the reset
duration. Limiting the min clk frequency looks like the less invasive
solution to me. Touching the DT isn't recommend.

Best regards