linux-kernel - Re: [PATCH v3 08/10] clk: ns2: add clock support for Broadcom Northstar 2 SoC

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Date:	Thu, 15 Oct 2015 14:25:49 -0700
From:	Scott Branden <sbranden@...adcom.com>
To:	Ray Jui <rjui@...adcom.com>, Jon Mason <jonmason@...adcom.com>
CC:	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	"Hauke Mehrtens" <hauke@...ke-m.de>, <linux-clk@...r.kernel.org>,
	<devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	<bcm-kernel-feedback-list@...adcom.com>
Subject: Re: [PATCH v3 08/10] clk: ns2: add clock support for Broadcom
 Northstar 2 SoC

On 15-10-15 02:15 PM, Ray Jui wrote:
>
>
> On 10/15/2015 2:10 PM, Jon Mason wrote:
>> On Thu, Oct 15, 2015 at 02:04:09PM -0700, Scott Branden wrote:
>>> Hi Ray,
>>>
>>> Comment at near end.
>>>
>>> On 15-10-15 01:55 PM, Ray Jui wrote:
>>>>
>>>>
>>>> On 10/15/2015 1:40 PM, Scott Branden wrote:
>>>>> We need some sort of kconfig option to differentiate NS2 clock driver
>>>> >from being pulled in all the time.
>>>>>
>>>>> On 15-10-15 12:48 PM, Jon Mason wrote:
>>>>>> The Broadcom Northstar 2 SoC is architected under the iProc
>>>>>> architecture. It has the following PLLs: GENPLL SCR, GENPLL SW,
>>>>>> LCPLL DDR, LCPLL Ports, all derived from an onboard crystal.
>>>>>>
>>>>>> Signed-off-by: Jon Mason <jonmason@...adcom.com>
>>>>>> ---
>>>>>>    drivers/clk/Makefile                |   2 +-
>>>>>>    drivers/clk/bcm/Makefile            |   1 +
>>>>>>    drivers/clk/bcm/clk-ns2.c           | 288
>>>>>> ++++++++++++++++++++++++++++++++++++
>>>>>>    include/dt-bindings/clock/bcm-ns2.h |  72 +++++++++
>>>>>>    4 files changed, 362 insertions(+), 1 deletion(-)
>>>>>>    create mode 100644 drivers/clk/bcm/clk-ns2.c
>>>>>>    create mode 100644 include/dt-bindings/clock/bcm-ns2.h
>>>>>>
>>>>>> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
>>>>>> index d08b3e5..6124bd3 100644
>>>>>> --- a/drivers/clk/Makefile
>>>>>> +++ b/drivers/clk/Makefile
>>>>>> @@ -47,7 +47,7 @@ obj-$(CONFIG_COMMON_CLK_WM831X)        += clk-wm831x.o
>>>>>>    obj-$(CONFIG_COMMON_CLK_XGENE)        += clk-xgene.o
>>>>>>    obj-$(CONFIG_COMMON_CLK_PWM)        += clk-pwm.o
>>>>>>    obj-$(CONFIG_COMMON_CLK_AT91)        += at91/
>>>>>> -obj-$(CONFIG_ARCH_BCM)            += bcm/
>>>>>> +obj-y                    += bcm/
>>>>>>    obj-$(CONFIG_ARCH_BERLIN)        += berlin/
>>>>>>    obj-$(CONFIG_ARCH_HISI)            += hisilicon/
>>>>>>    obj-$(CONFIG_ARCH_MXC)            += imx/
>>>>>> diff --git a/drivers/clk/bcm/Makefile b/drivers/clk/bcm/Makefile
>>>>>> index e258b28..2d1cbc5 100644
>>>>>> --- a/drivers/clk/bcm/Makefile
>>>>>> +++ b/drivers/clk/bcm/Makefile
>>>>>> @@ -3,6 +3,7 @@ obj-$(CONFIG_CLK_BCM_KONA)    += clk-kona-setup.o
>>>>>>    obj-$(CONFIG_CLK_BCM_KONA)    += clk-bcm281xx.o
>>>>>>    obj-$(CONFIG_CLK_BCM_KONA)    += clk-bcm21664.o
>>>>>>    obj-$(CONFIG_COMMON_CLK_IPROC)    += clk-iproc-armpll.o
>>>>>> clk-iproc-pll.o clk-iproc-asiu.o
>>>>>> +obj-$(CONFIG_COMMON_CLK_IPROC)    += clk-ns2.o
>>>>>
>>>>> NS2 code is dragged in for all IPROC SoCs.  We need a config option for
>>>>> NS2 (CONFIG_ARCH_BCM_NS2) to avoid this (if Arnd allows this for ARMv8
>>>>> processors... ?).
>>>>>
>>>>> You can see below ARMv7 processors don't have this problem.
>>>>>
>>>>
>>>> The arm64 maintainers (Catalin, Mark, and etc.) stated they only want
>>>> one ARCH options per chip family.
>>>>
>>>>> If not we need to add CONFIG_CLK_NS2.
>>>>
>>>> If using CONFIG_CLK_NS2, how is it going to be enabled/selected?
>>>
>>> Since CONFIG_ARCH_BCM_NS2 isn't "allowed" to be introduced we will
>>> need to create and select a CONFIG_CLK_BCM_NS2 in the defconfig
>>> instead.
>>
>> Is this better than the binary becoming slightly bigger?  I thought
>> the extra complexity was worse than having an unused chunk of clk code
>> (and Kona is already doing the same thing above).  I believe Ray was
>> in agreement with me during the internal review of this code.
>>
>> Thanks,
>> Jon
>>
>
> Yes, I'm okay with leaving it as it is. I even prefer changing the
> current Makefile to make all iProc based core clock drivers and SoC
> specific clock tables under CONFIG_COMMON_CLK_IPROC, which is what some
> of the other vendors do.
>
I'd leave it exactly as is then rather than pulling in more dead code 
when not needed.  This ns2 clock code is very minor compared to other 
code bloat in the kernel and drivers.
>>>>
>>>> Ray
>>>>
>>>
>>> Regards,
>>>   Scott

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