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Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7

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  Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7 Tomasz Figa <tomasz.figa@gmail.com> - 2015-11-19 05:20 +0100
    Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7 Krzysztof Kozlowski <k.kozlowski@samsung.com> - 2015-11-19 06:00 +0100
      Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7 Tomasz Figa <tomasz.figa@gmail.com> - 2015-11-19 10:20 +0100
        Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on  ARMv7 Krzysztof Kozlowski <k.kozlowski@samsung.com> - 2015-11-19 10:50 +0100
        Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7 Sylwester Nawrocki <s.nawrocki@samsung.com> - 2015-11-19 12:10 +0100

#1272832 — Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7

Hi Krzysztof,

Good idea, just a couple of nits inline. Other than that:

Acked-by: Tomasz Figa <tomasz.figa@gmail.com>

2015-11-16 10:36 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@samsung.com>:
> Currently the Exynos5433 (ARMv8 SoC) clock driver depends on ARCH_EXYNOS
> so it is built also on ARMv7. This does not bring any kind of benefit.
> There won't be a single kernel image for ARMv7 and ARMv8 SoCs (like
> multi_v7 for ARMv7).
>
> Instead build clock drivers only for respective SoC's architecture.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> ---
>  drivers/clk/samsung/Kconfig  | 13 +++++++++++++
>  drivers/clk/samsung/Makefile |  4 ++--
>  2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/samsung/Kconfig b/drivers/clk/samsung/Kconfig
> index 84196ecdaa12..5f138fc4d84d 100644
> --- a/drivers/clk/samsung/Kconfig
> +++ b/drivers/clk/samsung/Kconfig
> @@ -2,6 +2,7 @@ config COMMON_CLK_SAMSUNG
>         bool
>         select COMMON_CLK
>
> +# ARMv7 SoCs:

nit: I'm not aware of any recent upgrade of the S3C24xx line-up to
ARMv7 cores. ;) I'd suggest "32-bit ARM SoCs" or just "ARM SoCs"...

>  config S3C2410_COMMON_CLK
>         bool
>         select COMMON_CLK_SAMSUNG
> @@ -24,3 +25,15 @@ config S3C2443_COMMON_CLK
>         bool
>         select COMMON_CLK_SAMSUNG
>
> +# ARMv8 SoCs:

and then here "64-bit ARM SoCs" or "ARM64 SoCs", whichever you prefer.
I'd lean towards simple "ARM" and "ARM64".

> +config EXYNOS5433_COMMON_CLK
> +       bool
> +       depends on ARM64 || COMPILE_TEST
> +       default ARCH_EXYNOS

nit: bool and default can be combined into def_bool ARCH_EXYNOS

> +       select COMMON_CLK_SAMSUNG
> +
> +config EXYNOS7_COMMON_CLK
> +       bool
> +       depends on ARM64 || COMPILE_TEST
> +       default ARCH_EXYNOS

nit: See above.

However, I don't think we can disable compilation of particular 64-bit
SoCs, so maybe there isn't much sense in splitting their clock drivers
into separate symbols?

Best regards,
Tomasz
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#1272851

On 19.11.2015 13:18, Tomasz Figa wrote:
> Hi Krzysztof,
> 
> Good idea, just a couple of nits inline. Other than that:
> 
> Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
> 
> 2015-11-16 10:36 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@samsung.com>:
>> Currently the Exynos5433 (ARMv8 SoC) clock driver depends on ARCH_EXYNOS
>> so it is built also on ARMv7. This does not bring any kind of benefit.
>> There won't be a single kernel image for ARMv7 and ARMv8 SoCs (like
>> multi_v7 for ARMv7).
>>
>> Instead build clock drivers only for respective SoC's architecture.
>>
>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>> ---
>>  drivers/clk/samsung/Kconfig  | 13 +++++++++++++
>>  drivers/clk/samsung/Makefile |  4 ++--
>>  2 files changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/clk/samsung/Kconfig b/drivers/clk/samsung/Kconfig
>> index 84196ecdaa12..5f138fc4d84d 100644
>> --- a/drivers/clk/samsung/Kconfig
>> +++ b/drivers/clk/samsung/Kconfig
>> @@ -2,6 +2,7 @@ config COMMON_CLK_SAMSUNG
>>         bool
>>         select COMMON_CLK
>>
>> +# ARMv7 SoCs:
> 
> nit: I'm not aware of any recent upgrade of the S3C24xx line-up to
> ARMv7 cores. ;) I'd suggest "32-bit ARM SoCs" or just "ARM SoCs"...

okay

> 
>>  config S3C2410_COMMON_CLK
>>         bool
>>         select COMMON_CLK_SAMSUNG
>> @@ -24,3 +25,15 @@ config S3C2443_COMMON_CLK
>>         bool
>>         select COMMON_CLK_SAMSUNG
>>
>> +# ARMv8 SoCs:
> 
> and then here "64-bit ARM SoCs" or "ARM64 SoCs", whichever you prefer.
> I'd lean towards simple "ARM" and "ARM64".

ARM64 sounds good.

> 
>> +config EXYNOS5433_COMMON_CLK
>> +       bool
>> +       depends on ARM64 || COMPILE_TEST
>> +       default ARCH_EXYNOS
> 
> nit: bool and default can be combined into def_bool ARCH_EXYNOS
> 

Right.

>> +       select COMMON_CLK_SAMSUNG
>> +
>> +config EXYNOS7_COMMON_CLK
>> +       bool
>> +       depends on ARM64 || COMPILE_TEST
>> +       default ARCH_EXYNOS
> 
> nit: See above.
> 
> However, I don't think we can disable compilation of particular 64-bit
> SoCs, so maybe there isn't much sense in splitting their clock drivers
> into separate symbols?

To me it does not really matter. Indeed as you said one cannot disable
building of one particular Exynos SoCs.

However we could still want not build some parts of such SoCs (like
clock, pinctrl etc). I don't see much benefit for such case except when
someone would like to drastically reduce the size of kernel image (for
whatever reasons he has.).

On the other hand having separate symbols causes duplication and
obfuscates a little the Kconfig/Makefile. I like keeping things simple
so one symbol for all ARM64 Exynos clocks sounds good.

Sylwester preferred current approach. You and Pankaj seem to prefer one
symbol-way.

Should we make a voting? :)

Best regards,
Krzysztof
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#1272951

2015-11-19 13:51 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@samsung.com>:
> On 19.11.2015 13:18, Tomasz Figa wrote:
>> However, I don't think we can disable compilation of particular 64-bit
>> SoCs, so maybe there isn't much sense in splitting their clock drivers
>> into separate symbols?
>
> To me it does not really matter. Indeed as you said one cannot disable
> building of one particular Exynos SoCs.
>
> However we could still want not build some parts of such SoCs (like
> clock, pinctrl etc). I don't see much benefit for such case except when
> someone would like to drastically reduce the size of kernel image (for
> whatever reasons he has.).

Can we really build a kernel that support selected Exynos SoC without
its clock driver? Actually I don't think we even allow deselecting
clock drivers currently, because they are not visible in menuconfig.
Unless there is a clear goal to separate ARCH level Kconfig symbol for
particular ARM64-based Exynos SoCs, I don't think it makes any sense
to keep the clock-related symbols separate.

>
> On the other hand having separate symbols causes duplication and
> obfuscates a little the Kconfig/Makefile. I like keeping things simple
> so one symbol for all ARM64 Exynos clocks sounds good.
>
> Sylwester preferred current approach. You and Pankaj seem to prefer one
> symbol-way.

Hmm, I read Sylwester's post as a reply to your original message and
not Pankaj's. Sylwester, could you clarify?

Best regards,
Tomasz
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#1272969 — Re: [PATCH 1/2] clk: samsung: Don't build ARMv8 clock drivers on ARMv7

W dniu 19.11.2015 o 18:16, Tomasz Figa pisze:
> 2015-11-19 13:51 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@samsung.com>:
>> On 19.11.2015 13:18, Tomasz Figa wrote:
>>> However, I don't think we can disable compilation of particular 64-bit
>>> SoCs, so maybe there isn't much sense in splitting their clock drivers
>>> into separate symbols?
>>
>> To me it does not really matter. Indeed as you said one cannot disable
>> building of one particular Exynos SoCs.
>>
>> However we could still want not build some parts of such SoCs (like
>> clock, pinctrl etc). I don't see much benefit for such case except when
>> someone would like to drastically reduce the size of kernel image (for
>> whatever reasons he has.).
> 
> Can we really build a kernel that support selected Exynos SoC without
> its clock driver? Actually I don't think we even allow deselecting
> clock drivers currently, because they are not visible in menuconfig.
> Unless there is a clear goal to separate ARCH level Kconfig symbol for
> particular ARM64-based Exynos SoCs, I don't think it makes any sense
> to keep the clock-related symbols separate.

That is reasonable and very convincing. I'll wait for Sylwester reply
before re-spinning.

BR,
Krzysztof
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#1273037

On 19/11/15 10:16, Tomasz Figa wrote:
> 2015-11-19 13:51 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@samsung.com>:
>> > On 19.11.2015 13:18, Tomasz Figa wrote:
>>> >> However, I don't think we can disable compilation of particular
>>> >> 64-bit SoCs, so maybe there isn't much sense in splitting their 
>>> >> clock drivers into separate symbols?
>> >
>> > To me it does not really matter. Indeed as you said one cannot 
>> > disable building of one particular Exynos SoCs.
>> >
>> > However we could still want not build some parts of such SoCs (like
>> > clock, pinctrl etc). I don't see much benefit for such case except
>> > when someone would like to drastically reduce the size of kernel 
>> > image (for whatever reasons he has.).
>
> Can we really build a kernel that support selected Exynos SoC without
> its clock driver? Actually I don't think we even allow deselecting
> clock drivers currently, because they are not visible in menuconfig.
> Unless there is a clear goal to separate ARCH level Kconfig symbol for
> particular ARM64-based Exynos SoCs, I don't think it makes any sense
> to keep the clock-related symbols separate.
> 
>> >
>> > On the other hand having separate symbols causes duplication and
>> > obfuscates a little the Kconfig/Makefile. I like keeping things 
>> > simple so one symbol for all ARM64 Exynos clocks sounds good.
>> >
>> > Sylwester preferred current approach. You and Pankaj seem to prefer
>> > one symbol-way.
>
> Hmm, I read Sylwester's post as a reply to your original message and
> not Pankaj's. Sylwester, could you clarify?

OK, let's just use a common clk Kconfig symbol for Exynos ARM64.

What I tried to say is that with addition of support for few more
of those SoCs the kernel image size can easily grow by 1MB order,
due to just clk drivers inclusion. Perhaps it's not a big issue
with current hardware configuration.
Maybe in long term we should think about splitting CMU drivers
into a built-in critical clocks part and the rest in loadable
modules.

-- 
Thanks,
Sylwester
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