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Subject: Re: [PATCH] ARM64: Kconfig: Fix the missing hi655x common clk
To:     Riku Voipio <riku.voipio@linaro.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        open list <linux-kernel@vger.kernel.org>,
        Wei Xu <xuwei5@hisilicon.com>,
        John Stultz <john.stultz@linaro.org>,
        Olof Johansson <olof@lixom.net>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@lists.infradead.org>
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From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <ffc8ca90-3678-98d5-74dc-eb1411536b21@linaro.org>
Date:   Wed, 21 Feb 2018 11:34:31 +0100
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On 21/02/2018 11:30, Riku Voipio wrote:
> On 16 February 2018 at 19:35, Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
>> On 12/06/2017 23:12, Arnd Bergmann wrote:
>>> On Mon, Jun 12, 2017 at 11:38 AM, Daniel Lezcano
>>> <daniel.lezcano@linaro.org> wrote:
>>>> On Fri, Jun 09, 2017 at 10:48:13PM +0200, Arnd Bergmann wrote:
>>>>> On Fri, Jun 9, 2017 at 10:15 PM, John Stultz <john.stultz@linaro.org> wrote:
>>>>>> On Fri, Jun 9, 2017 at 1:06 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>>>>> On Fri, Jun 9, 2017 at 5:46 PM, Daniel Lezcano
>>>>>>> <daniel.lezcano@linaro.org> wrote:
>>>>>>>
>>>>>>> Yes, but I'm not sure this is the right patch either. We tend to not
>>>>>>> use 'select' for user-visible drivers, and most hisilicon platforms
>>>>>>> won't need this driver.
>>>>>>>
>>>>>>> I think it would be more consistent to add this to the defconfig
>>>>>>> and regard it as a user error when the driver is disabled on a
>>>>>>> machine that needs it.
>>>>>>
>>>>>> Maybe the select is not exactly in the right place, but I don't really
>>>>>> feel like a pmic on an SoC is a "user-visible driver". I deal with the
>>>>>> board often and when the new dependency was made on the clk, I would
>>>>>> have never have found it on my own w/o Ulf and Daniel pointing out
>>>>>> what I needed to enable.
>>>>>
>>>>> What I meant is that the Kconfig option is user-visible. On a very high
>>>>> level, this is a result of arch/arm64/Kconfig.platforms listing only
>>>>> very broad categories of SoCs, in many cases only the manufacturers
>>>>> of very different chip families, which then control the visibility of the
>>>>> individual Kconfig items for things like pinctrl or clk.
>>>>>
>>>>> I now see that MFD_HI655X_PMIC is the top-level driver that you
>>>>> have to select before enabling COMMON_CLK_HI655X, so the
>>>>> patch is actually broken unless it actually selects both.
>>>>>
>>>>> How about simply adding a 'default MFD_HI655X_PMIC' to
>>>>> COMMON_CLK_HI655X to enable it unless it is explicitly
>>>>> turned off?
>>>>
>>>> Actually, I share John's opinion.
>>>>
>>>> Ideally when we choose a platform, all the relevants devices configuration
>>>> options should be selected automatically from a single topmost node of a tree
>>>> (platform selection) to all the nodes corresponding to the devices, leaving the
>>>> user to select one simple option without knowledge of the SoC hardware
>>>> internals.
>>>>
>>>> If the user is expert in the platform and knows exactly what he does, then he
>>>> can select an _EXPERT_ like option and be able to disable some drivers.
>>>>
>>>> It is how I tend to write the Kconfig options, so the 'default MFD_HI655X_PMIC'
>>>> is confusing for me. Wouldn't make sense to select COMMON_CLK_HI655X when
>>>> MFD_HI655X_PMIC is enabled?
>>>
>>> I don't think it's that easy. When you do that, MFD_HI655X_PMIC gains
>>> a dependency on COMMON_CLK and will again cause a warning on
>>> machines that disable that during compile testing.
>>>
>>> Using 'select' for user-selectable options generally leads to problems,
>>> and you are better off avoiding it. If you want to make the symbol impossible
>>> to turn off for non-EXPERT configurations, you can write it like
>>>
>>> config COMMON_CLK_HI655X
>>>         tristate "Clock driver for Hi655x" if EXPERT
>>>         depends on (MFD_HI655X_PMIC || COMPILE_TEST)
>>>         depends on REGMAP
>>>         default MFD_HI655X_PMIC
>>>
>>> That way the option is completely hidden for non-EXPERT,
>>> but still has the right default otherwise, and the dependencies
>>> are tracked right for compile-testing.
>>
>> What about the options:
> 
> First, as distros, automatic selection down from selecting ARCH_X is
> preferred over
> defconfigs. However, we also prefer to build everything possible as
> modules, so "default Y"
> is sometimes too strong.
> 
>> CONFIG_HI3660_MBOX
>> CONFIG_HI6220_MBOX
> 
> These are tristate and platorms can boot without them.
> 
>> CONFIG_STUB_CLK_HI6220
>> CONFIG_STUB_CLK_HI3660
> 
> These are bool, so default Y is ok.
> 
>> Would make sense to do something like:
> 
>>
>> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
>> index b9546ab..3a07dfe 100644
>> --- a/arch/arm64/configs/defconfig
>> +++ b/arch/arm64/configs/defconfig
>> @@ -517,7 +517,6 @@ CONFIG_COMMON_CLK_CS2000_CP=y
>>  CONFIG_COMMON_CLK_S2MPS11=y
>>  CONFIG_CLK_QORIQ=y
>>  CONFIG_COMMON_CLK_PWM=y
>> -CONFIG_STUB_CLK_HI3660=y
>>  CONFIG_COMMON_CLK_QCOM=y
>>  CONFIG_QCOM_CLK_SMD_RPM=y
>>  CONFIG_IPQ_GCC_8074=y
>> @@ -529,8 +528,6 @@ CONFIG_HWSPINLOCK_QCOM=y
>>  CONFIG_ARM_MHU=y
>>  CONFIG_PLATFORM_MHU=y
>>  CONFIG_BCM2835_MBOX=y
>> -CONFIG_HI3660_MBOX=y
>> -CONFIG_HI6220_MBOX=y
>>  CONFIG_ROCKCHIP_IOMMU=y
>>  CONFIG_ARM_SMMU=y
>>  CONFIG_ARM_SMMU_V3=y
>> diff --git a/drivers/clk/hisilicon/Kconfig b/drivers/clk/hisilicon/Kconfig
>> index 1bd4355..becdb1d 100644
>> --- a/drivers/clk/hisilicon/Kconfig
>> +++ b/drivers/clk/hisilicon/Kconfig
>> @@ -44,14 +44,17 @@ config RESET_HISI
>>           Build reset controller driver for HiSilicon device chipsets.
>>
>>  config STUB_CLK_HI6220
>> -       bool "Hi6220 Stub Clock Driver"
>> -       depends on COMMON_CLK_HI6220 && MAILBOX
>> -       default ARCH_HISI
>> +       bool "Hi6220 Stub Clock Driver" if EXPERT
>> +       depends on (COMMON_CLK_HI6220 || COMPILE_TEST)
>> +       depends on MAILBOX
>> +       default COMMON_CLK_HI6220
>>         help
>>           Build the Hisilicon Hi6220 stub clock driver.
>>
>>  config STUB_CLK_HI3660
>> -       bool "Hi3660 Stub Clock Driver"
>> -       depends on COMMON_CLK_HI3660 && MAILBOX
>> +       bool "Hi3660 Stub Clock Driver" if EXPERT
>> +       depends on (COMMON_CLK_HI3660 || COMPILE_TEST)
>> +       depends on MAILBOX
>> +       default COMMON_CLK_HI3660
>>         help
>>           Build the Hisilicon Hi3660 stub clock driver.
>> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
>> index de8390d4..8d1726c 100644
>> --- a/drivers/mailbox/Kconfig
>> +++ b/drivers/mailbox/Kconfig
>> @@ -109,16 +109,19 @@ config TI_MESSAGE_MANAGER
>>           platform has support for the hardware block.
>>
>>  config HI3660_MBOX
>> -       tristate "Hi3660 Mailbox"
>> -       depends on ARCH_HISI && OF
>> +       tristate "Hi3660 Mailbox" if EXPERT
>> +       depends on (ARCH_HISI || COMPILE_TEST)
>> +       depends on OF
>> +       default ARCH_HISI
>>         help
>>           An implementation of the hi3660 mailbox. It is used to send message
>>           between application processors and other processors/MCU/DSP. Select
>>           Y here if you want to use Hi3660 mailbox controller.
> 
> Which kernel tree is this from? I don't see this driver in mainline.

Yes, that's right. The HI6220 part is ok but the HI3660 is still not
mainline yet.


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