linux-kernel - Re: [PATCH v6 4/5] ARM: DTS: da850: Add cfgchip syscon node

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Message-ID: <m2wpgs5h63.fsf@baylibre.com>
Date:   Fri, 28 Oct 2016 13:53:40 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     David Lechner <david@...hnology.com>
Cc:     Sekhar Nori <nsekhar@...com>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Axel Haslam <ahaslam@...libre.com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 4/5] ARM: DTS: da850: Add cfgchip syscon node

David Lechner <david@...hnology.com> writes:

> On 10/28/2016 12:08 PM, Kevin Hilman wrote:
>> Sekhar Nori <nsekhar@...com> writes:
>>
>>> On Wednesday 26 October 2016 09:38 PM, David Lechner wrote:
>>>> On 10/25/2016 10:06 PM, David Lechner wrote:
>>>>> Add a syscon node for the SoC CFGCHIPn registers. This is needed for
>>>>> the new usb phy driver.
>>>>>
>>>>> Signed-off-by: David Lechner <david@...hnology.com>
>>>>> ---
>>>>>  arch/arm/boot/dts/da850.dtsi | 4 ++++
>>>>>  1 file changed, 4 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm/boot/dts/da850.dtsi b/arch/arm/boot/dts/da850.dtsi
>>>>> index f79e1b9..6bbf20d 100644
>>>>> --- a/arch/arm/boot/dts/da850.dtsi
>>>>> +++ b/arch/arm/boot/dts/da850.dtsi
>>>>> @@ -188,6 +188,10 @@
>>>>>              };
>>>>>
>>>>>          };
>>>>> +        cfgchip: cfgchip@...7c {
>>>>
>>>> I wonder if there is a more generic name instead of cfgchip@. Is there a
>>>> preferred generic name for syscon nodes?
>>>
>>> I did not find anything in ePAPR, but chip-controller might be more
>>> appropriate.
>>>
>>>>
>>>>> +            compatible = "ti,da830-cfgchip", "syscon";
>>>
>>> Looks like we need "simple-mfd" too in the compatible list?
>>>
>>> I think we can also fold patch 5/5 into this patch and add the cfgchip
>>> along with USB phy child node included.
>>>
>>> If you respin the patch, I can drop 4/5 and 5/5 that I have queued and
>>> included the updated patch instead.
>>
>> Sekhar, what's your opinion of having this syscon just for CFGCHIP* vs
>> a single syscon for the whole SYSCFG0 region.
>>
>> The drivers/bus driver from Bartosz is also using SYSCFG0 registers, and
>> proposing a sysconf ro this region, but it will need to exclude the
>> CFGCHIPn registers if we also have this syscon.
>
> What about the pinmux registers, which are already being used
> separately too?

I guess I/we need to have a closer look at how these are actually shared
and decide if there are really overlapping users.  here are several
different registers packed into this region, but it may be the case that
there really isn't any overlapping usage (e.g. pinmux vs. PHY vs bus
priorities, etc.)

>>
>> I tend to think we should just have one for the whole SYSCFG0 which
>> this series could use.
>>
>> Unfortunately, the PHY driver is already merged and it references the
>> syscon by compatible.  The PHY driver should probably be fixed to find
>> its syscon by phandle, and then maybe we could move to a single syscon
>> for SYSCFG0?
>
> I agree that this should be change, but I was thinking we should use
> syscon_node_to_regmap(np->parent) since the phy node should be a child
> of the syscon node.

Even better.

Kevin