linux-kernel - Re: [PATCH v9 2/6] mfd: mp2629: Add support for mps battery charger

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Date:   Thu, 30 Apr 2020 12:39:49 +0200
From:   saravanan sekar <sravanhome@...il.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     andy.shevchenko@...il.com, robh+dt@...nel.org, jic23@...nel.org,
        knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
        sre@...nel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v9 2/6] mfd: mp2629: Add support for mps battery charger

Hi Lee,

On 27/04/20 11:30 am, saravanan sekar wrote:
> Hi Lee,
>
> On 27/04/20 10:51 am, Lee Jones wrote:
>> On Fri, 24 Apr 2020, saravanan sekar wrote:
>>
>>> On 24/04/20 12:53 pm, Lee Jones wrote:
>>>> On Fri, 24 Apr 2020, saravanan sekar wrote:
>>>>
>>>>> Hi Lee,
>>>>>
>>>>> On 24/04/20 11:37 am, Lee Jones wrote:
>>>>>> On Fri, 24 Apr 2020, saravanan sekar wrote:
>>>>>>
>>>>>>> Hi Lee,
>>>>>>>
>>>>>>> On 24/04/20 9:18 am, Lee Jones wrote:
>>>>>>>> On Wed, 15 Apr 2020, Saravanan Sekar wrote:
>>>>>>>>
>>>>>>>>> mp2629 is a highly-integrated switching-mode battery charge 
>>>>>>>>> management
>>>>>>>>> device for single-cell Li-ion or Li-polymer battery.
>>>>>>>>>
>>>>>>>>> Add MFD core enables chip access for ADC driver for battery 
>>>>>>>>> readings,
>>>>>>>>> and a power supply battery-charger driver
>>>>>>>>>
>>>>>>>>> Signed-off-by: Saravanan Sekar <sravanhome@...il.com>
>>>>>>>>> ---
>>>>>>>>>      drivers/mfd/Kconfig        |  9 ++++
>>>>>>>>>      drivers/mfd/Makefile       |  2 +
>>>>>>>>>      drivers/mfd/mp2629.c       | 86 
>>>>>>>>> ++++++++++++++++++++++++++++++++++++++
>>>>>>>>>      include/linux/mfd/mp2629.h | 19 +++++++++
>>>>>>>>>      4 files changed, 116 insertions(+)
>>>>>>>>>      create mode 100644 drivers/mfd/mp2629.c
>>>>>>>>>      create mode 100644 include/linux/mfd/mp2629.h
>>>>>>>> How is this driver registered?
>>>>>>>>
>>>>>>>> Looks like it has device tree support.  Is there another way?
>>>>>>> Yes, only using device tree
>>>>>> Then how about using 'simple-mfd' and 'syscon'?
>>>>>>
>>>>>> Then you can omit this driver completely.
>>>>> The exception is to support for non device tree platform as well, 
>>>>> but I have
>>>>> tested only for ARM device tree platform.
>>>> Is that a reality though?
>>>>
>>>> How else do you see this realistically being registered?
>>>>
>>> I understand that acpi related device table are not covered here, 
>>> well I
>>> don't have to platform to test so.
>>> If you ask me to cover acpi related table, I can do but hard to test.
>> I don't know of any reasons why syscon can't be used by ACPI.
>>
>> Please try to solve this issue using 'simple-mfd' and 'syscon'.
> Well the simple-mfd and syscon topic recommended by you when Device 
> tree alone is used.
> I wounder still I receive review/improvements comments for this mfd 
> patch and also another
> to omit this driver using simple-mfd (rework the series).
> Confused, not sure which is valid and will be accepted at the end.

I had look into syscon, as far my understanding syscon is supported only 
for memory mapped IO. MP2629
device is over I2C bus, could you share your thought about syscon for 
this device?

Thanks,
Saravanan