[U-Boot] [PATCH 2/2] powerpc/mpc85xx: modify erratum A007212

[York Sun <yorksun@freescale.com>]

On 9/27/14 6:56 PM, "Zhao Qiang-B45475" <qiang.zhao@freescale.com> wrote:

>On 09/27/2014 12:02 AM, York Sun wrote:
>> -----Original Message-----
>> From: Sun York-R58495
>> Sent: Saturday, September 27, 2014 12:02 AM
>> To: Zhao Qiang-B45475; u-boot at lists.denx.de
>> Cc: Xie Xiaobo-R63061
>> Subject: Re: [PATCH 2/2] powerpc/mpc85xx: modify erratum A007212
>> 
>> On 09/25/2014 10:55 PM, Zhao Qiang-B45475 wrote:
>> >
>> > On 9/26/14 1:01 PM, York Sun wrote:
>> >
>> >> -----Original Message-----
>> >> From: Sun York-R58495
>> >> Sent: Friday, September 26, 2014 1:01 PM
>> >> To: Zhao Qiang-B45475; u-boot at lists.denx.de
>> >> Cc: Xie Xiaobo-R63061; Zhao Qiang-B45475
>> >> Subject: Re: [PATCH 2/2] powerpc/mpc85xx: modify erratum A007212
>> >>
>> >> On 9/25/14 9:37 PM, "Zhao Qiang" <B45475@freescale.com> wrote:
>> >>
>> >>> T2080 v1.0 has this errata while v1.1 has fixed this errata by
>> >>> hardware, add a new function to check the SVR_SOC_VER, SVR_MAJ and
>> >>> SVR_MIN first, if the cpu is T2080 and version is not v1.0, doesn't
>> >>> run the a007212 errata_workaround.
>> >>>
>> >>> Signed-off-by: Zhao Qiang <B45475@freescale.com>
>> >>> ---
>> >>
>> >>
>> >> Qiang,
>> >>
>> >> I don't agree with your analysis.
>> >>
>> >> This workaround has two parts. One part is to to disable DDR PLL in
>> RCW.
>> >> The second part is to detect DDR PLL is disabled and to implement the
>> >> software workaround to bring DDR up. U-boot has the second part, it
>> >> is safe to apply to all versions for affected SoC. I put in the
>> comments.
>> >> Your patch detects the SVR and decide if the workaround should be
>> applied.
>> >> This is wrong. It should detect if DDR PLL is disabled. In case an
>> >> old RCW is used, you don't want to end up with a dead board because
>> >> DDR is disabled.
>> >
>> > OK , got it , I will modify it for v2.
>> > Thanks for you comment.
>> >
>> 
>> Qiang,
>> 
>> I don't think you even need a patch for this. The logic for u-boot code
>> is:
>> 
>> Regardless of the SVR, the workaround is not be applied if RCW doesn't
>> disable DDR PLL.
>> Regardless of the SVR, the workaround is and should be applied if RCW
>> disables DDR PLL.
>
>And how about the file arch/powerpc/cpu/mpc85xx/speed.c.
>The code doesn?t detect if the DDR PLL is disabled, it will config the
>mem_pll_rat.

If you look closely in this file, you will see code guarded by macro
CONFIG_SYS_FSL_ERRATUM_A007212. In case mem_pll_rat is detected as 0, a
reserved field is used for DDR PLL ratio. It is written in erratum
workaround. It wasn't in original document but should be updated a while
ago.

York

>>