Re: [PATCH 2/2] power: supply: Add Lenovo Yoga C630 EC driver

From: Daniel Thompson <daniel.thompson@linaro.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Sebastian Reichel <sre@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH 2/2] power: supply: Add Lenovo Yoga C630 EC driver
Date: Mon, 12 Sep 2022 17:00:17 +0000	[thread overview]
Message-ID: <20220912165802.dvlf3eeqx5g3bzdm@maple.lan> (raw)
In-Reply-To: <20220810030500.2793882-3-bjorn.andersson@linaro.org>

On Tue, Aug 09, 2022 at 10:05:00PM -0500, Bjorn Andersson wrote:
> The Qualcomm Snapdragon-based Lenovo Yoga C630 has some sort of EC
> providing AC-adapter and battery status, as well as USB Type-C altmode
> notifications for Displayport operation.

There's a couple of minor review comments but before we get to that:
woo hoo!

> The Yoga C630 ships with Windows, where these operations primarily are
> implemented in ACPI, but due to various issues with the hardware
> representation therein it's not possible to run Linux on this
> information. As such this is a best-effort re-implementation of these
> operations, based on the register map expressed in ACPI and a fair
> amount of trial and error.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> Reported-by: kernel test robot <lkp@intel.com>
> ---
>  drivers/power/supply/Kconfig        |  11 +
>  drivers/power/supply/Makefile       |   1 +
>  drivers/power/supply/yoga-c630-ec.c | 547 ++++++++++++++++++++++++++++
>  3 files changed, 559 insertions(+)
>  create mode 100644 drivers/power/supply/yoga-c630-ec.c
>
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index 1aa8323ad9f6..6e706e948ad2 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -897,4 +897,15 @@ config BATTERY_UG3105
>  	  device is off or suspended, the functionality of this driver is
>  	  limited to reporting capacity only.
>
> +config LENOVO_YOGA_C630_EC
> +	tristate "Lenovo Yoga C630 EC battery driver"
> +	depends on DRM
> +	depends on I2C

This needs a "depends on TYPEC" in order to avoid linker errors.

> +	help
> +	  Driver for the Embedded Controller in the Qualcomm Snapdragon-based
> +	  Lenovo Yoga C630, which provides battery information and USB Type-C
> +	  altmode notifications.
> +
> +	  Say M or Y here to include this support.
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/yoga-c630-ec.c b/drivers/power/supply/yoga-c630-ec.c
> new file mode 100644
> index 000000000000..1fa0b5844e01
> --- /dev/null
> +++ b/drivers/power/supply/yoga-c630-ec.c
> @@ -0,0 +1,547 @@
> <snip>
> +static int yoga_c630_ec_bat_get_property(struct power_supply *psy,
> +					 enum power_supply_property psp,
> +					 union power_supply_propval *val)
> +{
> +	struct yoga_c630_ec *ec = power_supply_get_drvdata(psy);
> +	int rc = 0;
> +
> +	if (ec->bat_present)
> +		yoga_c630_ec_maybe_update_bat_status(ec);
> +	else if (psp != POWER_SUPPLY_PROP_PRESENT)
> +		return -ENODEV;
> +
> +	switch (psp) {
>       <snip>
> +	case POWER_SUPPLY_PROP_TECHNOLOGY:
> +		val->intval = POWER_SUPPLY_TECHNOLOGY_LION;
> +		break;
> +	case POWER_SUPPLY_PROP_MODEL_NAME:
> +		val->strval = "PABAS0241231";
> +		break;
> +	case POWER_SUPPLY_PROP_MANUFACTURER:
> +		val->strval = "Compal";
> +		break;
> +	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
> +		val->strval = "05072018";
> +		break;

I'm a little sceptical that hardcoding a serial number into the
driver provides anybody any benefit (regardless of whether the
AML code does this). AFAICT this is not a commonly implemented property
in other power supplies so I'm not clear why this is needed.

Daniel.