linux-kernel - Re: [PATCH v2 3/6] clk: ti: dra7: Add clkctrl clock data for the mcan clocks

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Message-ID: <6df7e0cd-5574-aa19-6c99-4438e5e377e0@ti.com>
Date:   Mon, 4 Jun 2018 19:28:01 +0530
From:   Faiz Abbas <faiz_abbas@...com>
To:     Tony Lindgren <tony@...mide.com>
CC:     Tero Kristo <t-kristo@...com>, Rob Herring <robh@...nel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-clk@...r.kernel.org>, <bcousson@...libre.com>,
        <paul@...an.com>
Subject: Re: [PATCH v2 3/6] clk: ti: dra7: Add clkctrl clock data for the mcan
 clocks

Hi,

On Friday 01 June 2018 07:56 PM, Tony Lindgren wrote:
> * Faiz Abbas <faiz_abbas@...com> [180601 06:49]:
>> Hi,
>>
>> On Thursday 31 May 2018 06:59 PM, Tero Kristo wrote:
>>> On 31/05/18 13:14, Faiz Abbas wrote:
>>>> Hi,
>>>>
>>>> On Thursday 31 May 2018 09:33 AM, Rob Herring wrote:
>>>>> On Wed, May 30, 2018 at 07:41:30PM +0530, Faiz Abbas wrote:
>>>>>> Add clkctrl data for the m_can clocks and register it within the
>>>> ...
>>>>>>   diff --git a/include/dt-bindings/clock/dra7.h
>>>>>> b/include/dt-bindings/clock/dra7.h
>>>>>> index 5e1061b15aed..d7549c57cac3 100644
>>>>>> --- a/include/dt-bindings/clock/dra7.h
>>>>>> +++ b/include/dt-bindings/clock/dra7.h
>>>>>> @@ -168,5 +168,6 @@
>>>>>>   #define DRA7_COUNTER_32K_CLKCTRL    DRA7_CLKCTRL_INDEX(0x50)
>>>>>>   #define DRA7_UART10_CLKCTRL    DRA7_CLKCTRL_INDEX(0x80)
>>>>>>   #define DRA7_DCAN1_CLKCTRL    DRA7_CLKCTRL_INDEX(0x88)
>>>>>> +#define DRA7_ADC_CLKCTRL    DRA7_CLKCTRL_INDEX(0xa0)
>>>>>
>>>>> ADC and mcan are the same thing?
>>>>>
>>>>
>>>> The register to control MCAN clocks is called ADC_CLKCTRL, Yes.
>>>
>>> Is there any reason for this or is that just a documentation bug?
>>>
>>
>> Looks like they meant to have an ADC in dra74 or dra72 but decided
>> against it and then many years later used the same registers for MCAN
>> instead. You can see ADC_CLKCTRL exists in dra72 TRM but is explicitly
>> disabled.
>>
>> http://www.ti.com/lit/ug/spruic2b/spruic2b.pdf pg:1524
> 
> How about make add also something like to dra7.h:
> 
> #define DRA7_MCAN_CLKCTRL DRA7_ADC_CLKCTRL
> 
> And you can add a comment to the dts file to avoid people
> getting confused with this constantly.
> 

I would prefer to follow the TRM so that people don't look for registers
that don't exist at all.

Thanks,
Faiz