Re: [PATCH v2 3/4] ddr: imx: Allow to call ddr init without logging failure

On 8/20/26 8:34 AM, Frieder Schrempf wrote:
> On 19.08.26 14:47, Marek Vasut wrote:
>> On 8/19/26 12:10 PM, Frieder Schrempf wrote:
>>> On 19.08.26 12:04, Marek Vasut wrote:
>>>> On 8/19/26 9:07 AM, Frieder Schrempf wrote:
>>>>> From: Frieder Schrempf <[email protected]>
>>>>>
>>>>> In some cases we need to call ddr_init() multiple times to try
>>>>> different configurations.
>>>>
>>>> What different configurations ? Details please ?
>>>
>>> The detection of different DDR types/sizes on our SoMs has always been
>>> based on trying the init and seeing if it succeeds, falling back to the
>>> smaller sizes on failure. See here [1].
>> Could you maybe bring the interface up in some minimal 400 MTps or 100
>> MTps configuration and then read out the MR ID registers from the DRAM
>> to discern which DRAM configuration is present on your SoM? This would
>> be the ideal generic way of doing this, and it would be reliable since
>> the IDs are stable and surely indicate which DRAM chip and how big it is.
> 
> No, unfortunately this doesn't work. We already tried. The MR ID can't
> be used as we have single and dual rank setups that report the same ID.
> We have no way of knowing how many dies are connected unless we try it.

Is the controller unable to interact with each rank separately ? I would 
expect in single rank setup, that read of MR ID from one rank would pass 
and from the other rank it would fail ?