[U-Boot] [PATCH] ARM: OMAP5: DDR3: Change io settings

[Sricharan R <r.sricharan@ti.com>]

Hi,

On Wednesday 16 October 2013 06:03 PM, Tom Rini wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
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> On 10/16/2013 07:34 AM, Enric Balletbo Serra wrote:
>> Hi Sricharan,
>>
>> 2013/10/16 Sricharan R <r.sricharan@ti.com>:
>>> Changing the IO settings to turn on VREF_DQ and
>>> disable weak pullup for DQS/nDQS.
>>>
>>> Signed-off-by: Sricharan R <r.sricharan@ti.com>
>>> ---
>>>  arch/arm/include/asm/arch-omap5/omap.h |    4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/arch-omap5/omap.h b/arch/arm/include/asm/arch-omap5/omap.h
>>> index 414d37a..3c2306f 100644
>>> --- a/arch/arm/include/asm/arch-omap5/omap.h
>>> +++ b/arch/arm/include/asm/arch-omap5/omap.h
>>> @@ -145,9 +145,9 @@ struct s32ktimer {
>>>  #define DDR_IO_2_VREF_CELLS_DDR3_VALUE                         0x0
>>>
>>>  #define DDR_IO_I_40OHM_SR_SLOWEST_WD_DQ_NO_PULL_DQS_NO_PULL_ES2 0x7C7C7C7C
>>> -#define DDR_IO_I_40OHM_SR_FAST_WD_DQ_NO_PULL_DQS_NO_PULL_ES2 0x64656465
>>> +#define DDR_IO_I_40OHM_SR_FAST_WD_DQ_NO_PULL_DQS_NO_PULL_ES2 0x64646464
>>>  #define DDR_IO_0_VREF_CELLS_DDR3_VALUE_ES2 0xBAE8C631
>>> -#define DDR_IO_1_VREF_CELLS_DDR3_VALUE_ES2 0xB46318D8
>>> +#define DDR_IO_1_VREF_CELLS_DDR3_VALUE_ES2 0xBC6318DC
>>>  #define DDR_IO_2_VREF_CELLS_DDR3_VALUE_ES2 0x84210000
>>>
>>>  #define EFUSE_1 0x45145100
>> Sorry for my ignorance, I just want to know more ...
>>
>> What's the purpose of this patch ? Solves any DDR3 problem on OMAP5 ? Improves ?
> I suspect I know what this is about, but can we please have a more
> verbose commit message here?

Above the two changes improved DDR3 stability at extended temperature
ranges above 83C.

1) The first change from 0x64656465 to 0x64646464 removes the weak pull
     on the DQ lines. Otherwise the DQ line was not staying at Vref when IDLE (retreats
     to ground) and because of this there were extra transitions and noise.

 2) The second change was to enable internal VREF_DQ_OUT which otherwise was at 0V.

Hope this helps. BTW, i will repost with a better commit log. Sorry.

Regards,
 Sricharan