[U-Boot] [PATCH] mmc/dwmmc: remove recursive FIFO threshold setup

[Jaehoon Chung <jh80.chung@samsung.com>]

Hi, Alexey.

On 11/27/2013 04:45 PM, Alexey Brodkin wrote:
> Hi Pantelis,
> 
> On Wed, 2013-11-27 at 09:21 +0200, Pantelis Antoniou wrote:
>> Hi Alexey,
>>
>> On Nov 27, 2013, at 9:11 AM, Alexey Brodkin wrote:
>>
> 
>> ATM if no host->fifoth_val value is provided the code will calculate one and write it.
>> Otherwise it will write the one configured.
> 
> Indeed. But what I faced - if you try to run U-Boot more than 1 time
> after powering up your board then this calculated value will be
> calculated improperly. And in my comment to the patch itself I described
> it.
I understood your point. It's possible. If we set to calculated value, 
then it's set to value lower than previous value. right?
if host->fifoth_val is always used somewhere, this value should be fixed.
But host->fifoth val was not used anywhere, so need to calculate the value.
This is problem.

Best Regards,
Jaehoon Chung

> 
> So there're 2 options:
> 1. Re-implement calculation in such a way so it gets the same value on
> 2nd, 3rd and other U-Boot runs. Moreover it's not clear to me how this
> calculation is intended to work?
> 
> We take some initial value and then modify it - note it's not simply
> overrided with some value, but initial/default value is read from the
> register, then goes some math, and then we put new value back.
> 
> How do we know which value/configuration was by default so we do
> particular modifications later? What is a logic behind this?
> 
> So why we need this functionality (unclear reconfiguration) if default
> register value works flawlessly in majority of cases and for some corner
> cases users may specify their custom value that will simply override
> default value.
> 
>>> Still I have a couple of questions to you:
>>> 1. Why there's no example/instance of "host->fifoth_val" setup/usage in
>>> U-Boot source tree? If there was at least one I would leave
>>> "host->fifoth_val".
>>>
>>
>> I would guess it's because everyone uses the default setting of 0 which
>> results in a somewhat sane value.
> 
> Regards,
> Alexey
>