Re: [PATCH v3 00/10] power: supply: max77693: Toggle charging/OTG based on extcon status

[Henrik Grimler <henrik@grimler.se>]

Hi Artur,

On Mon, Jul 29, 2024 at 07:47:34PM +0200, Artur Weber wrote:
> This patchset does the following:
> 
> - Add CURRENT_MAX and INPUT_CURRENT_MAX power supply properties to
>   expose the "fast charge current" (maximum current from charger to
>   battery) and "CHGIN input current limit" (maximum current from
>   external supply to charger).
> 
> - Add functions for toggling charging and OTG modes.
> 
> - Add an extcon-based handler that enables charging or OTG depending
>   on the cable type plugged in. The extcon device to use for cable
>   detection can be specified in the device tree, and is entirely
>   optional.
> 
> The extcon listener implementation is inspired by the rt5033 charger
> driver (commit 8242336dc8a8 ("power: supply: rt5033_charger: Add cable
> detection and USB OTG supply")).

Tested on exynos4412-i9305 (after applying the changes in patch 8 - 10
to exynos4412-midas.dtsi).  It works well, device correctly identifies
a usb cable connected to charger or a usb cable connected to computer,
and sets a limit of 1.8 A and 0.5 A in the two cases.

I did notice that device does not always detect cable insertion, so I
can occassionally get two de-attach events in a row.  Cable was
inserted between 428 and 462 in below log snippet:

[  389.458399] max77693-muic max77693-muic: external connector is attached(chg_type:0x3, prev_chg_type:0x3)
[  389.469765] max77693-charger max77693-charger: fast charging. connector type: 6
[  428.151857] max77693-muic max77693-muic: external connector is detached(chg_type:0x3, prev_chg_type:0x0)
[  428.160319] max77693-charger max77693-charger: not charging. connector type: 13
[  462.156048] max77693-muic max77693-muic: external connector is detached(chg_type:0x0, prev_chg_type:0x0)
[  469.881925] max77693-muic max77693-muic: external connector is attached(chg_type:0x3, prev_chg_type:0x3)
[  469.890049] max77693-charger max77693-charger: fast charging. connector type: 6

but this is probably an issue in extcon driver though rather than
charger.

I have not tested so that MHL still works, as I do not have access to
that cable at the moment, will try it in a few days.

Best regards
Henrik Grimler

> Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
> 
> v3 no longer uses the CHARGER regulator to manage the power status, and
> that's for two reasons:
> 
> - Regulator enable/disable behavior was interfering with how the power
>   supply driver worked (we occasionally got "unbalanced disables"
>   errors when switching charging state, despite checking for the
>   regulator status with regulator_is_enabled() - the CHARGER reg would
>   report as enabled despite the enable count being 0).
>   This broke OTG insertion if the OTG cable was plugged in first, and
>   sometimes caused warnings on unsuspend.
> 
> - Changing the charging values directly in the power supply driver is
>   less opaque and lets us avoid bringing in a dependency on regulators.
> 
> It also splits the current limits back into two properties:
> INPUT_CURRENT_LIMIT and CONSTANT_CHARGE_CURRENT_MAX. Again, there are
> two reasons for this split:
> 
> - They are two separate current controls, one for USB->charger and one
>   for charger->battery, and they have different limits (0-2.1A for CC
>   vs 60mA-2.58A for input). Given that the power supply core has the
>   properties for both values separately, it's more logical to present
>   them as such.
> 
> - It's safer to keep these separate; CONSTANT_CHARGE_CURRENT_MAX is
>   pretty explicitly only set *once* - at probe time with a safe value
>   specified in the DT. This way, INPUT_CURRENT_LIMIT is safer to modify
>   since in the event of an invalid value the CC current will hold back
>   the extra current thus preventing damage to the battery.
> 
> The latter is relevant as I'm working on a follow-up patchset that
> allows for controlling the charging parameters using power supply
> properties/sysfs properties rather than the CHARGER regulator.
> 
> Note that the CHARGER regulator gets disabled automatically if it's
> not used, which will disable charging if it was auto-enabled by the
> extcon code. This can be worked around by re-attaching the cable, or
> more properly by removing the CHARGER regulator from DT for devices
> that use the extcon-based charger management, as has been done in the
> Galaxy Tab 3 8.0 DTSI.
> 
> See v1 for old description:
> 
> https://lore.kernel.org/r/20240530-max77693-charger-extcon-v1-0-dc2a9e5bdf30@gmail.com
> ---
> Changes in v3:
> - Drop uses of CHARGER regulator, manage registers directly in power
>   supply driver instead
> - Link to v2: https://lore.kernel.org/r/20240715-max77693-charger-extcon-v2-0-0838ffbb18c3@gmail.com
> 
> Changes in v2:
> - Changed to use monitored-battery for charge current value
> - Both current limit variables are now set by the CHARGER regulator
> - Link to v1: https://lore.kernel.org/r/20240530-max77693-charger-extcon-v1-0-dc2a9e5bdf30@gmail.com
> 
> ---
> Artur Weber (10):
>       dt-bindings: power: supply: max77693: Add monitored-battery property
>       dt-bindings: power: supply: max77693: Add maxim,usb-connector property
>       power: supply: max77693: Expose input current limit and CC current properties
>       power: supply: max77693: Set charge current limits during init
>       power: supply: max77693: Add USB extcon detection for enabling charging
>       power: supply: max77693: Add support for detecting and enabling OTG
>       power: supply: max77693: Set up charge/input current according to cable type
>       ARM: dts: samsung: exynos4212-tab3: Add battery node with charge current value
>       ARM: dts: samsung: exynos4212-tab3: Add USB connector node
>       ARM: dts: exynos4212-tab3: Drop CHARGER regulator
> 
>  .../bindings/power/supply/maxim,max77693.yaml      |  15 +
>  arch/arm/boot/dts/samsung/exynos4212-tab3.dtsi     |  22 +-
>  drivers/power/supply/Kconfig                       |   1 +
>  drivers/power/supply/max77693_charger.c            | 302 ++++++++++++++++++++-
>  include/linux/mfd/max77693-private.h               |  12 +
>  5 files changed, 337 insertions(+), 15 deletions(-)
> ---
> base-commit: 0c3836482481200ead7b416ca80c68a29cfdaabd
> change-id: 20240525-max77693-charger-extcon-9ebb7bad83ce
> 
> Best regards,
> -- 
> Artur Weber <aweber.kernel@gmail.com>
>