[PATCHv6] ARM: dts: add exynos5422-cpus.dtsi to correct cpu order

[Chanho Park]

Hi,

On Tue, Jul 14, 2015 at 5:23 PM, Kukjin Kim <kgene at kernel.org> wrote:
> Chanho Park wrote:
>>
>> Hi Kukjin,
>>
>> On Tue, Jul 14, 2015 at 2:04 PM, Kukjin Kim <kgene at kernel.org> wrote:
>> > Krzysztof Kozlowski wrote:
>> >>
>> >> On 14.07.2015 09:24, Chanho Park wrote:
>> >> > The odroid-xu3 board which is based on exynos5422 not exynos5800 is
>> >> > booted from cortex-a7 core unlike exynos5800. The odroid-xu3's cpu order
>> >> > is quite strange. cpu0 and cpu5-7 are cortex-a7 cores and cpu1-4 are
>> >> > cortex-a15 cores. To correct this mis-odering, I added exynos5422-cpus.dtsi
>> >> > and reversing cpu orders from exynos5420. Now, cpu0-3 are cortex-a7 and
>> >> > cpu4-7 are cortex-a15.
>> >> >
>> >> > Reviewed-by: Krzysztof Kozlowski <k.kozlowski at samsung.com>
>> >> > Signed-off-by: Chanho Park <parkch98 at gmail.com>
>> >> > ---
>
> [...]
>
>> >> >
>> >> > Secondary cpu booting problem[1] is not resolved yet. Need more investigations
>> >> > to work booting 8 cores correctly.
>> >> >
>> >> > [1]: http://www.spinics.net/lists/linux-samsung-soc/msg45525.html
>> >> >
>> >> >  arch/arm/boot/dts/exynos5422-cpus.dtsi             | 81 ++++++++++++++++++++++
>> >> >  arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi |  1 +
>> >> >  2 files changed, 82 insertions(+)
>> >> >  create mode 100644 arch/arm/boot/dts/exynos5422-cpus.dtsi
>> >>
>> >> Thanks, applied to my tree. I'll send it to Kukjin for v4.3 unless he
>> >> picks it also.
>> >>
>> > Well, let me see. I'm thinking we need to sort out the cpu ordering and dtsi
>> > inclusions for exynos5420, 5422 and 5800 related to DT files.
>> >
>> > See,
>> >
>> > 1) exynos5420 DT (cpu0~3: a15, cpu 4~7: a7)
>> > 2) exynos5800 DT is including exynos5420 DT
>> > 3) exynos5422 and exynos5800 based boards are including exynos5800 DT.
>> >
>> > Then making exynos5422-cpus DT for exynos5422 based boards?
>> > (cpu0~3: a7, cpu4~7: a15)
>> >
>> > I think, it could cause confusion when new board based on them are added
>> > because it's not clear and the boot cpu could be selected by bootloader part.
>>
>> The iROM will check the GPIO pin to select which core is run as cpu0.
>> I think no one will change the GPIO pin if a new board which is based
>> on exynos5422 :)
>>
> Yes, I know the boot sequence and it means it depends on board configuration
> not SoC. That’s why I'm saying it should be handled in board DT file. I think,
> most of current exynos big.LITTLE model should do if it could be changed
> according to board configuration.

I also agreed it's not a SoC configuration since second
patch(exynos5422.dtsi -> exynos5422-cpu.dtsi).

>
>> >
>> > So how about creating exynos5422-cpus and exynos5420-cpus then including the
>> > cpus DT file in each board accordingly?
>> >
>> > Or more clear way to avoid confusion?
>>
>> In this situation, all exynos5422 boards(odroid xu3 series and mobile
>> phone) have same cpu configurations. If we move the exynos5420 cpu
>> configuration from exynos5420.dtsi, we should change all dts which
>> including exynos5420.dtsi.
>
> Maybe same board configuration. Just adding inclusion should be fine at this
> moment.
>
>> I think we'd better to defer the change until a new exynos5422 board
>> which has different cpu configurations is added.
>>
> I mean, according to current inclusion of exynos5422 based boards' DT file, it
> is including exynos5420 DT via exynos5800 DT and then override different cpu
> ordering (5422-cpu DT) because of different board configuration (just GPIO
> value) and it is not a good way in this case.

Actually, I don't want to disturb current dts hierarchy even though it
looks strange. The common features of exynos5800 and exynos5422 should
be in the exynos5800.dtsi because they shared many things except the
cpu order.
Please consider the exynos5422-cpu.dtsi is just board configurations
to represent cpu order.

-- 
Best Regards,
Chanho Park