[U-Boot] [PATCH] powerpc/t1040qds: Add DDR Raw Timing support

[Priyanka Jain]

Ok,
I will drop this patch and maintain it locally.

Regards
Priyanka


> -----Original Message-----
> From: sun york-R58495
> Sent: Thursday, October 31, 2013 10:50 AM
> To: Jain Priyanka-B32167
> Cc: sun york-R58495; u-boot at lists.denx.de; Aggrwal Poonam-B10812
> Subject: Re: [PATCH] powerpc/t1040qds: Add DDR Raw Timing support
> 
> 
> On Oct 30, 2013, at 9:55 PM, Jain Priyanka-B32167 wrote:
> 
> >
> >> -----Original Message-----
> >> From: sun york-R58495
> >> Sent: Wednesday, October 30, 2013 10:14 PM
> >> To: Jain Priyanka-B32167; u-boot at lists.denx.de
> >> Cc: Aggrwal Poonam-B10812
> >> Subject: Re: [PATCH] powerpc/t1040qds: Add DDR Raw Timing support
> >>
> >> On 10/25/2013 02:49 AM, Priyanka Jain wrote:
> >>> T1040QDS-D3 has dual-rank DDR:
> >>> 	Micron, MT18KSF51272AZ-1G6 (4GB, x72, CL=10).
> >>> Add Raw Timing structure for this DDR.
> >>>
> >>> Typically SPD method is used for getting DDR parameter and
> >>> calculating values for various DDR controller registers.
> >>>
> >>> But somentimes it may happen that SPD present on DDR may get
> >>> accidently erased or is not working properly during initial bring-up.
> >>> In that circumnstance, DDR raw timing structure can be use as
> >>> fallback option for getting DDR parameters.
> >>>
> >>> Signed-off-by: Poonam Aggrwal <poonam.aggrwal at freescale.com>
> >>> Signed-off-by: Priyanka Jain <Priyanka.Jain at freescale.com>
> >>> ---
> >>
> >> I don't think it is appropriate to use raw timing for this
> application.
> >> This board use DIMMs, not soldered DDR chips. In normal cases, this
> >> piece of code is not used. It is only useful if you have a DIMM
> >> without a valid SPD. You could get another DIMM. I am not saying this
> >> patch is wrong, it is just useless for general public.
> >>
> >> York
> >
> > [Jain Priyanka-B32167]  You are right that in case of DIMM type of
> memories, raw timing may not be required.
> > But there are certain scenarios in which keeping raw timing is useful
> > like 1)During initial bring-up, there is a possibility that I2C bus
> > may be broken, In that case boot-loader has to rely on the fallback
> option of raw timing.
> > 2)Also raw timings are used in emulator to test t1040.
> > So, we prefer to keep raw timing as fallback option.
> 
> It is a debug technique, not an implementation. You can use fixed
> register setting as well for debugging. But it doesn't mean you have to
> keep it in the final code. After you cleaning up the code, all "fixed"
> code should be removed, including the raw timing parameters you are
> using. Emulator target also has I2C EEPROM modeled. You should use SPD as
> well.
> 
> York