linux-kernel - Re: [PATCH v4 6/7] typec: tcpm: Represent source supply through power

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Date:   Tue, 30 Jan 2018 15:11:31 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sebastian Reichel <sre@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Yueyao Zhu <yueyao.zhu@...il.com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, support.opensource@...semi.com
Subject: Re: [PATCH v4 6/7] typec: tcpm: Represent source supply through
 power_supply class

Hi Adam,

On Tue, Jan 02, 2018 at 03:50:54PM +0000, Adam Thomson wrote:
> This commit adds a power_supply class instance to represent a
> PD source's voltage and current properties. This provides an
> interface for reading these properties from user-space or other
> drivers.
> 
> For PPS enabled Sources, this also provides write access to set
> the current and voltage and allows for swapping between standard
> PDO and PPS APDO.
> 
> As this represents a superset of the information provided in the
> fusb302 driver, the power_supply instance in that code is removed
> as part of this change, so reverting the commit titled
> 'typec: tcpm: Represent source supply through power_supply class'



> Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> ---
>  .../ABI/testing/sysfs-class-power-tcpm-source-psy  |  92 ++++++++
>  drivers/usb/typec/Kconfig                          |   1 +
>  drivers/usb/typec/fusb302/Kconfig                  |   2 +-
>  drivers/usb/typec/fusb302/fusb302.c                |  63 +-----
>  drivers/usb/typec/tcpm.c                           | 233 ++++++++++++++++++++-
>  5 files changed, 328 insertions(+), 63 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-power-tcpm-source-psy
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-power-tcpm-source-psy b/Documentation/ABI/testing/sysfs-class-power-tcpm-source-psy
> new file mode 100644
> index 0000000..4986cba
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-power-tcpm-source-psy
> @@ -0,0 +1,92 @@
> +What: 		/sys/class/power_supply/tcpm-source-psy/type
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-only property describes the main type of source supply.
> +	Type-C is a USB standard so this property always returns "USB".
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/connected_type
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-only property describes the type of source supply that is
> +	connected, if the supply is online. The value is always Type C
> +	unless a source has been attached which is identified as USB-PD capable.
> +
> +	Valid values:
> +		- "USB_TYPE_C"	: Type C connected supply, not UBS-PD capable
> +				  (default value)
> +		- "USB_PD"	: USB-PD capable source supply connected
> +		- "USB_PD_PPS"	: USB-PD PPS capable source supply connected
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/online
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-write property describes the online state of the source
> +	supply. When the value of this property is not 0, and the supply allows
> +	it, then it's possible to switch between online states (i.e. 1 -> 2,
> +	2 -> 1)
> +
> +	Valid values:
> +		- 0	: Offline, no source supply attached
> +		- 1	: Fixed Online, Type-C or USB-PD capable supply
> +			  attached, non-configurable current and voltage
> +			  properties in this state.
> +		- 2	: PPS Online, USB-PD PPS feature enabled, 'current_now'
> +			  and 'voltage_now' properties can be modified in this
> +			  state. Re-writing of this value again, once already
> +			  set, will re-request the same configured voltage and
> +			  current values. This can be used as a keep-alive for
> +			  the PPS connection.
> +			  [NOTE: This is value only selectable if
> +			   'connected_type' reports a value of "USB_PD_PPS"]
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/voltage_min
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-only property describes the minimum voltage the source supply
> +	can provide.
> +
> +	Value in microvolts.
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/voltage_max
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-only property describes the maximum voltage the source supply
> +	can provide.
> +
> +	Value in microvolts.
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/voltage_now
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-write property describes the voltage the source supply is
> +	providing now. This property can only be written to if the source supply
> +	is in online state '2' (PPS enabled), otherwise it's read-only
> +	information.
> +
> +	Value in microvolts.
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/current_max
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-only property describes the maximum current the source supply
> +	can provide.
> +
> +	Value in microamps.
> +
> +What: 		/sys/class/power_supply/tcpm-source-psy/current_now
> +Date:		December 2017
> +Contact:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> +Description:
> +	This read-write property describes the current the source supply can
> +	provide now. This property can only be written to if the source supply
> +	is in online state '2' (PPS enabled), otherwise it's read-only
> +	information.
> +
> +	Value in microamps.

I think those should be documented for the entire psy class, not just
for this driver.

> diff --git a/drivers/usb/typec/Kconfig b/drivers/usb/typec/Kconfig
> index bcb2744..1ef606d 100644
> --- a/drivers/usb/typec/Kconfig
> +++ b/drivers/usb/typec/Kconfig
> @@ -48,6 +48,7 @@ if TYPEC
>  config TYPEC_TCPM
>  	tristate "USB Type-C Port Controller Manager"
>  	depends on USB
> +	select POWER_SUPPLY

I'm a little bit uncomfortable with such a strong dependency on an
other subsystem that we may not always need, but let's see what
Guenter says.


Thanks,

-- 
heikki