linux-kernel - Re: [PATCH 4/4] dt-bindings: mfd: max8998: Add charger subnode binding

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Date:   Thu, 10 Jan 2019 21:11:35 +0100
From:   Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
To:     Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:     Sebastian Reichel <sre@...nel.org>, lgirdwood@...il.com,
        broonie@...nel.org, lee.jones@...aro.org, robh+dt@...nel.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 4/4] dt-bindings: mfd: max8998: Add charger subnode binding

Hi

On Thursday, 10 January 2019 18:47:11 CET Sylwester Nawrocki wrote:
> Hi,
> 
> On 5/1/18 16:43, Paweł Chmiel wrote:
> > On Tuesday, May 1, 2018 2:45:40 PM CEST Sebastian Reichel wrote:
> >> On Fri, Apr 27, 2018 at 06:03:02PM +0200, Paweł Chmiel wrote:
> >>> This patch adds devicetree bindings documentation for
> >>> battery charging controller as the subnode of MAX8998 PMIC.
> >>> It's based on current behavior of driver.
> >>>
> >>> Fixes: ee999fb3f17f ("mfd: max8998: Add support for Device Tree")
> >>> Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
> >>> ---
> >>>  Documentation/devicetree/bindings/mfd/max8998.txt | 22 ++++++++++++++++++++++
> >>>  1 file changed, 22 insertions(+)
> 
> >>> --- a/Documentation/devicetree/bindings/mfd/max8998.txt
> >>> +++ b/Documentation/devicetree/bindings/mfd/max8998.txt
> >>> @@ -50,6 +50,21 @@ Additional properties required if max8998,pmic-buck2-dvs-gpio is defined:
> >>>  - max8998,pmic-buck2-dvs-voltage: An array of 2 voltage values in microvolts
> >>>    for buck2 regulator that can be selected using dvs gpio.
> >>>  
> >>> +Charger: Configuration for battery charging controller should be added
> >>> +inside a child node named 'charger'.
> >>> +  Required properties:
> >>> +  - max8998,charge-eoc: Setup "End of Charge". If value equals 0,
> >>> +    remain value set from bootloader or default value will be used.
> >>> +    Valid values: 0, 10 - 45
> >>> +
> >>> +  - max8998,charge-restart: Setup "Charge Restart Level". If value equals 0,
> >>> +    remain value set from bootloader or default value will be used.
> >>> +    Valid values: -1, 0, 100, 150, 200
> 
> Perhaps change the property name to max8998,charge-restart-threshold, 
> in include/linux/mfd/max8998.h we have:
> 
>  * @restart: Restart Level in mV: 100, 150, 200, and -1 for disable.
>  *   If it equals 0, leave it unchanged.
> 
> Then we could make it an optional property:
> 
>  - max8998,charge-restart-threshold: Charge restart threshold in millivolts. 
>    Valid values are: 0, 100, 150, 200. If the value equals 0 the charger 
>    restart will be disabled.
> 
> If the property is missing the charger restart threshold configuration would
> be left unchanged.
> 
Strange, i've looked at max8998 and didn't saw information that those values are in mV (maybe it was from vendor sources).

> >>> +  - max8998,charge-timeout: Setup "Charge Full Timeout". If value equals 0,
> >>> +    remain value set from bootloader or default value will be used.
> >>> +    Valid values: -1, 0, 5, 6, 7
> >>
> >> What are those values? seconds?
> >>
> > Honestly i don't know. I've just documented values accepted currently 
> > by charger driver, so we can use it from devicetree.
> > I couldn't find any max8998 datasheet with this information (units, possible 
> > values etc for those properties).
> 
> The charge timeout is in hours, as described in include/linux/mfd/max8998.h:
> 
> 
> "* @timeout: Full Timeout in hours: 5, 6, 7, and -1 for disable.
>  *   If it equals 0, leave it unchanged.
>  *   Otherwise, leave it unchanged."
> 
> We could change description of the property to something along the lines of:
> 
> Optional properties:
> 
>   - max8998,charge-timeout: Charge timeout in hours. Valid values are:
>     0, 5, 6, 7. If the value is 0 the charge timer will be disabled.
> 
> Then if the property is missing the driver will leave charge timer configuration
> unchanged.
> 
> 
Thanks Sylwester Nawrocki for all those hints (mostly regarding units of those magic numbers/values). I'll prepare new version of those patches with all hints included.