[U-Boot] [PATCH] arch: ifc: update the IFC IP input clock

[york sun]

On 09/06/2016 07:42 PM, Prabhakar Kushwaha wrote:
>
>> -----Original Message-----
>> From: york sun
>> Sent: Tuesday, September 06, 2016 9:10 PM
>> To: Prabhakar Kushwaha <prabhakar.kushwaha at nxp.com>; u-
>> boot at lists.denx.de
>> Subject: Re: [PATCH] arch: ifc: update the IFC IP input clock
>>
>> On 09/06/2016 04:15 AM, Prabhakar Kushwaha wrote:
>>> IFC IP clock is always a constant divisor of platform clock
>>> pre-defined per SoC. Clock Control register (CCR) used in
>>> current implementation governs IFC IP output clock.
>>>
>>> So update IFC IP clock to be defined as per predefined clock
>>> divisor of platform clock.
>>>
>>> Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha at nxp.com>
>>> ---
>>>  README                                              |  3 +++
>>>  arch/arm/cpu/armv7/ls102xa/clock.c                  | 10 ++--------
>>>  arch/arm/cpu/armv8/fsl-layerscape/fsl_lsch2_speed.c | 10 ++--------
>>>  arch/arm/cpu/armv8/fsl-layerscape/fsl_lsch3_speed.c | 10 ++--------
>>>  arch/arm/include/asm/arch-fsl-layerscape/config.h   |  3 +++
>>>  arch/arm/include/asm/arch-ls102xa/config.h          |  1 +
>>>  arch/powerpc/cpu/mpc85xx/speed.c                    | 10 ++--------
>>>  arch/powerpc/include/asm/config_mpc85xx.h           |  9 +++++++++
>>>  8 files changed, 24 insertions(+), 32 deletions(-)
>>
>> Prabkahar,
>>
>> Two concerns here
>>
>> 1, it is not only IFC for powerpc. Older SoCs have local bus. That's why
>> the variable is named freq_localbus..
>>
>
> As per my understanding, Issue is valid for eLBC SoC also.
> Just wanted to confirm from internal IP team before spinning patch to fix it.
>
>> 2, what's the reason for this change? Is it wrong to use ccr to
>> calculate the clock? Or is it because recent Layerscape SoCs have
>> platform PLL different from platform clock? If the latter, can we limit
>> the fix to platform clock and not changing powerpc?
>>
>
> CCR governs the IFC output clock.
> This clock is used for synchronous NOR, NAND flashes. It is nowhere govern IFC IP internal clock.
>
> It is true since conception of IFC. Unfortunately code written is wrong since P1010.
> It is confusing everyone.
>

Are you saying the freq_localbus should be the internal clock, not 
output clock? As far as I can remember, this variable has always be used 
for output clock since 85xx. I am open to the idea to change to internal 
clock only if it makes sense. Browsing the code, I see this variable is 
used for information only, except for setting arch.lbc_clk.

York

York