[U-Boot] [PATCH v1 1/2] Revert "powerpc: mpc85xx: remove P2020DS board support"

[york sun]

On 02/01/2016 07:19 PM, Bin Meng wrote:
> Hi York,
> 
> On Tue, Feb 2, 2016 at 11:11 AM, york sun <york.sun at nxp.com> wrote:
>> On 02/01/2016 04:05 PM, Simon Glass wrote:
>> <snip>
>>>>
>>>> I will take this chance to convert P2020DS to use DM. Need some guidance here.
>>>> For NS16550, it needs the clock. To keep it simple, let's presume platform data
>>>> is used. My trouble is the clock is not unknown at compiling time. It needs to
>>>> be updated by checking the board/soc configuration after power up. The clock is
>>>> only available after get_clocks() is called in init_sequance. Is there a way I
>>>> can update the clocks before the driver is initialized?
>>>>
>>>> York
>>>
>>> See this commit:
>>>
>>> 858530a8     dm: tegra: Enable driver model for serial
>>>
>>> It sets up its own clock.
>>
>> Simon,
>>
>> Thanks for the pointer. I actually noticed this commit but it adds some
>> confusion to me. Take your code as an example
>>
>> U_BOOT_DRIVER(serial_ns16550) = {
>>        .name   = "serial_tegra20",
>>        .id     = UCLASS_SERIAL,
>>        .of_match = tegra_serial_ids,
>>        .ofdata_to_platdata = tegra_serial_ofdata_to_platdata,
>>        .platdata_auto_alloc_size = sizeof(struct ns16550_platdata),
>>        .priv_auto_alloc_size = sizeof(struct NS16550),
>>        .probe = ns16550_serial_probe,
>>        .ops    = &ns16550_serial_ops,
>> };
>>
>> The name "serial_ns16550" is not directly used anywhere. So I guess you didn't
>> have to name it as "serial_ns16550", right?
>>
> 
> The commit Simon gave was an old one. Now all ns16550 driver has been
> unified into one.
> 
>> One step forward, if I want to create a new driver, say "fsl_ns16550", I will
>> have to use ofdata_to_platdata to fill in plat->clock. But for majority powerpc
>> SoCs, we don't use device tree. We may start to use device tree on new products.
>> But it is probably not a good idea to force every platform to change.
>>
> 
> Please do not create a new driver for FSL chipset. Does FSL have any

That's a relief. I don't want to create a new driver just for the clock.

> plan to continue maintaining all these PowerPC SoCs in U-Boot? If yes,
> I believe the intention is to bring driver model and device tree to
> these boards.

I'd rather to add the device tree step by step, not all at once. And probably
leave some legacy boards behind.

> 
>> Is there another way to update plat->clock?
>>
> 
> You can define CONFIG_SYS_NS16550_CLK to a routine that gets the
> correct clock freq at runtime: eg: get_serial_clock()

Please explain in detail. I want to go down this path. For non-device tree
platforms (for the time being), doesn't U_BOOT_DEVICES evaluate the platdata at
compiling time? How can I use a routine as the clock for ns16550_platdata?
It is pretty simple for fixed clock, as I am looking at an example
arch/arm/cpu/armv7/am33xx/board.c.

York