[U-Boot] [PATCH 1/7] ARM: OMAP4+: emif: Detect SDRAM from SDRAM config register

[Tom Rini]

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On 02/01/2013 01:30 AM, R Sricharan wrote:
> On Thursday 31 January 2013 09:59 PM, Tom Rini wrote:
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>> 
>> On 01/31/2013 12:51 AM, R Sricharan wrote:
>>> From: Lokesh Vutla <lokeshvutla at ti.com>
>>> 
>>> Now SDRAM initialization is done on the basis of omap
>>> revision. Instead this should be done on basis of SDRAM type
>>> read from EMIF_SDRAM_CONFIG register. This will be helpful to
>>> avoid unnessecary cpu checks for new boards
>>> 
>>> Signed-off-by: R Sricharan <r.sricharan at ti.com> Signed-off-by: 
>>> Lokesh Vutla <lokeshvutla at ti.com>
>> 
>> Does this mean the ROM is already doing some basic EMIF 
>> programming here?  I swear I looked down this path before, when I
>> wanted to share this code with am33xx and the problem is that 
>> while the registers aren't reset on warm boot, on cold boot they
>>  always come up in a default value, for both DDR2 and DDR3.
>> 
>> Or are you able to get by as the platforms come up with
>> different default values?
>> 
> Not the ROMCODE, the default value for SDRAM_CONFIG register is 
> exported from control module register based on efuse settings. We 
> did see that this default value was correct depending upon LPDDR2 
> or DDR3 in the case of OMAP.

OK, good.

> So does this mean that am3xx did not have the logic to load this 
> register dynamically based on efuse settings ? If that is the only
>  exception, then we can hardcode the register during startup only 
> in that case. Except for this, where you able to use the 
> emif-common driver in your case ?

In my initial testing, it was not being setup correctly.  I think it
was between that, and trying to abstract out further the PM-related
changes there wasn't much common EMIF code left, so I set the project
aside at the time.  I'll try and take another whack at it as I know
someone is adding ti814x support currently and did find a good
match-up with this EMIF code rather than the am33xx version, so maybe
that will help me to see what's going on.

And with all of that:
Reviewed-by: Tom Rini <trini at ti.com>

- -- 
Tom
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