Samsung SoCs: preparation for single kernel

[Eric Miao]

On Wed, Jun 23, 2010 at 3:28 PM, Tony Lindgren <tony at atomide.com> wrote:
> * Eric Miao <eric.y.miao at gmail.com> [100623 03:48]:
>> On Wed, Jun 23, 2010 at 7:27 AM, Kyungmin Park <kmpark at infradead.org> wrote:
>> > To Ben,
>> >
>> > I really need single kernel for s5pc110 (cortex A8) and s5pc210
>> > (cortex A9) at least.
>> > Fortunately arm move to these approaches recently. but current Samsung
>> > SoCs not prepare these one.
>> >
>> > So I wonder do you have a plan or how to address these issues?
>> > How to assign the address at resources and use it at runtime?
>> >
>> > Personally I want to use cpu_is_*. but you reject it to use.
>> > Other way is that we can create the base address variables and assign
>> > it at init time.
>> >
>> > Please give your opinions.
>> >
>> > Thank you,
>> > Kyungmin Park
>> >
>> > e.g., cpu_is_* usage at OMAP tree
>> >
>> > static void omap_init_mcspi(void)
>> > {
>> >        if (cpu_is_omap44xx())
>> >                omap4_mcspi_fixup();
>> >
>> >        platform_device_register(&omap2_mcspi1);
>> >        platform_device_register(&omap2_mcspi2);
>> >
>> >        if (cpu_is_omap2430() || cpu_is_omap343x() || cpu_is_omap44xx())
>> >                omap2_mcspi3_init();
>> >
>> >        if (cpu_is_omap343x() || cpu_is_omap44xx())
>> >                omap2_mcspi4_init();
>> > }
>>
>> Just my two cents: cpu_is_*() can be used, but only when absolutely necessary.
>> The s3c does a CPU detection at startup, so I guess the usage of cpu_is_*()
>> can be even reduced.
>>
>> I'm not sure if the above case is a good reference or not. The omap_init_mcspi
>> is called from omap2_init_devices(), while the registration can actually be
>> made into the board init code when that device is used (some of the McSPIs are
>> not used, and it's not necessary to register them), and the differences be
>> handled in the driver.
>
> Few comments regarding the cpu_is_omap macros: The macros should really be
> soc_is_omapxxxx() instead cpu_is_omapxxxx().

Right, that will be more specific. cpu_is_* could be used only
with the ARM core, like cpu_is_arm946ejs(), ... And apparently
we all have abusively used it :-)

>
> Also, sprinkling these too much makes the code messy and hard to patch for
> new processors. So you should limit the use to very selected places during
> init, then set some flag like OMAP_HAS_MCSPI2 | OMAP_HAS_MCSPI3 or something
> similar.

Exactly.