Re: [PATCH v3 2/5] mfd: sec: Add support for S2MPS15 PMIC

From: Krzysztof Kozlowski
Date: Wed Oct 28 2015 - 09:44:22 EST

W dniu 28.10.2015 o 17:46, Lee Jones pisze:
> On Wed, 28 Oct 2015, Krzysztof Kozlowski wrote:
>> On 26.10.2015 23:34, Lee Jones wrote:
>>> On Mon, 26 Oct 2015, Alim Akhtar wrote:
>>>> From: Thomas Abraham <thomas.ab@xxxxxxxxxxx>
>>>> Add support for S2MPS15 PMIC which is similar to S2MPS11 PMIC. The S2MPS15
>>>> PMIC supports 27 LDO regulators, 10 buck regulators, RTC, three 32.768KHz
>>>> clock outputs and battery charger. This patch adds initial support for
>>>> LDO and buck regulators of S2MPS15 device.
>>>> Signed-off-by: Thomas Abraham <thomas.ab@xxxxxxxxxxx>
>>>> Signed-off-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx>
>>>> [Alim: Added s2mps15_devs like rtc and clk and related changes]
>>>> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
>>>> ---
>>>> drivers/mfd/sec-core.c | 31 +++++++
>>>> drivers/mfd/sec-irq.c | 8 ++
>>>> include/linux/mfd/samsung/core.h | 1 +
>>>> include/linux/mfd/samsung/s2mps15.h | 158 +++++++++++++++++++++++++++++++++++
>>>> 4 files changed, 198 insertions(+)
>>>> create mode 100644 include/linux/mfd/samsung/s2mps15.h
>>> I replied to the previous set and won't be reviewing this one until
>>> all of the open points are solved.
>> The naming and compatibles used by the driver are confusing but how it
>> was at beginning. Beside the confusion, the names are correct:
>> 1. Main mfd driver:
>> - compatible: samsung,s2mps1*-pmic
>> - driver name: sec_pmic
>> 2. Regulator driver:
>> - no compatible (because it always searches for "regulators" subnode of
>> its parent... that is the convention/legacy behaviour)
>> - driver name: s2mps1*-pmic
>> I hope that explains your concerns.
> It explains *why*, but doesn't ease my concerns in any way.
> Unfortunately I've only just realised the disparity we have between
> MFD and the Regulator subsystem, which is annoying because it's now
> almost impossible to rectify.
> We should have taken one of two views. Either a) The MFD is the PMIC
> device which encompasses regulator control. In which case the MFD
> and it's corresponding compatible string would be named *-pmic and the
> regulator driver would be called *-regulator. Or b) The MFD could be
> considered a normal MFD and be named after the model number, then the
> regulator 'could' be named *-pmic.
> However, with reference to b), how much other Power Management does
> the regulator driver do besides control regulators? I suspect not
> much. Therefore my preference would be for a). My second choice
> would be a mixuture of the two where nothing gets named *-pmic. The
> last option on my list would be the current situation where we seem to
> be calling both the MFD (PMIC) itself and the Regulator driver
> *-pmic, which is not good.

Starting from the description of device-family. This is called "Power
Management IC" but it is rather a "Power Deliver/Distribute IC". There
isn't any logic inside except enable/disable/configure/set low power
mode for regulators.

However in the same time the IC comes (always) with:
- 32kHz clocks,
- RTC,
- backup battery charger (no driver for it),
- reset for SoC,
- shutdown on thermal alert (also no driver for this control).

The solution a) seems fine to me. Make sense and it looks entirely
backward compatible - only driver names will be modified.

Best regards,

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