[PATCH 2/2] [RFC] clk: stm32mp1: Handle SoC speed grade configs

[Marek Vasut <marex@denx.de>]

On 5/13/20 2:23 PM, Patrick DELAUNAY wrote:
> Hi Marek,
> 
>> From: Marek Vasut <marex@denx.de>
>> Sent: mercredi 13 mai 2020 12:53
>>
>> On 5/13/20 11:12 AM, Patrick DELAUNAY wrote:
>>> Dear Marek,
>>>
>>>> From: Marek Vasut <marex@denx.de>
>>>> Sent: mardi 12 mai 2020 19:07
>>>>
>>>> There are two speed grades of the STM32MP1, the A/C and D/F, the
>>>> former can run up to 650 MHz, the later at up to 800 MHz. Allow
>>>> specifying PLL config for both in the DT, so that it is possible to
>>>> cater for boards which can be populated with either SoC.
>>>>
>>>> Signed-off-by: Marek Vasut <marex@denx.de>
>>>> Cc: Patrick Delaunay <patrick.delaunay@st.com>
>>>> Cc: Patrice Chotard <patrice.chotard@st.com>
>>>> ---
>>>>  drivers/clk/clk_stm32mp1.c | 30 ++++++++++++++++++++++++++----
>>>>  1 file changed, 26 insertions(+), 4 deletions(-)
>>>>
> 
> [...]
> 
>>>
>>> The 2 speed grade will be supported with OPP information and HW
>>> support,present in kernel device tree (upstream in progress)
>>>
>>> I port this patch in U-Boot with:
>>> http://patchwork.ozlabs.org/project/uboot/patch/20200421171123.2.Id362
>>> 0aec4deb419f1c1a5876b865556e86d3aba1 at changeid/
>>>
>>>
>>> Please check the full serie
>>> stm32mp1: use OPP information for PLL1 settings in SPL
>>> http://patchwork.ozlabs.org/project/uboot/list/?series=171767
>>>
>>> PLL1 settings are now computed in SPL and no more read from DT.
>>
>> That's even better, nice, thanks !
>>
>> btw. does the D/F 800 MHz always set BIT(7) in the CPU ID , while the A/C 650
>> MHz part never does ? Maybe you can use that to discern the speed grades
>> instead of listing all the parts ...
> 
> Yes but the meaning of RPN (the part of CPU IP) is undocumented... 
> And BIT(7) could be no more be valid for next products.
> 
> So I prefer use the documented value of Device Part Number (RPN) as a fixed value.
>  
> For example:
> 
> Bits 7:0 RPN_coding[7:0]:
> 0x00: STM32MP157Cx
> 0x01: STM32MP157Ax
> 0x80: STM32MP157Fx
> 0x81: STM32MP157Dx
> Others: Reserved
> 
> And it is also requested by ST marketing team
> (don't code on RPN bit decoding).
> 
> Even if I agree: it is more elegant than my switch case.

And it saves a few bytes in SPL size ;-)