[PATCH v3 0/2] Fix Goodix touchscreen power leakage for MT8186 boards

[PATCH v3 0/2] Fix Goodix touchscreen power leakage for MT8186 boards

[Fei Shao]

These changes are based on the series in [1], which modified the
i2c-hid-of-goodix driver and removed the workaround for a power leakage
issue, so the issue revisits on Mediatek MT8186 boards (Steelix).

The root cause is that the touchscreen can be powered in different ways
depending on the hardware designs, and it's not as easy to come up with
a solution that is both simple and elegant for all the known designs.

To address the issue, I ended up adding a new boolean property for the
driver so that we can control the power up/down sequence depending on
that.

Adding a new property might not be the cleanest approach for this, but
at least the intention would be easy enough to understand, and it
introduces relatively small change to the code and fully preserves the
original control flow.
I hope this is something acceptable, and I'm open to any better
approaches.

[1] https://lore.kernel.org/all/20230207024816.525938-1-dianders@chromium.org/

Changes in v3:
- In power-down, only skip the GPIO but not the regulator calls if the
  flag is set

Changes in v2:
- Use a more accurate property name and with "goodix," prefix.
- Do not change the regulator_enable logic during power-up.

Fei Shao (2):
  dt-bindings: input: goodix: Add "goodix,no-reset-during-suspend"
    property
  HID: i2c-hid: goodix: Add support for "goodix,no-reset-during-suspend"
    property

 .../bindings/input/goodix,gt7375p.yaml           |  9 +++++++++
 drivers/hid/i2c-hid/i2c-hid-of-goodix.c          | 16 +++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

-- 
2.40.1.495.gc816e09b53d-goog

[PATCH v3 1/2] dt-bindings: input: goodix: Add "goodix,no-reset-during-suspend" property

[Fei Shao]

We observed that on Chromebook device Steelix, if Goodix GT7375P
touchscreen is powered in suspend (because, for example, it connects to
an always-on regulator) and with the reset GPIO asserted, it will
introduce about 14mW power leakage.

To address that, we add this property to skip reset during suspend.
If it's set, the driver will stop asserting the reset GPIO during
power-down. Refer to the comments in the driver for details.

Signed-off-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
---

(no changes since v2)

Changes in v2:
- Use a more accurate property name and with "goodix," prefix.

 .../devicetree/bindings/input/goodix,gt7375p.yaml        | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
index ce18d7dadae2..1edad1da1196 100644
--- a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
+++ b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
@@ -43,6 +43,15 @@ properties:
       itself as long as it allows the main board to make signals compatible
       with what the touchscreen is expecting for its IO rails.
 
+  goodix,no-reset-during-suspend:
+    description:
+      Set this to true to enforce the driver to not assert the reset GPIO
+      during suspend.
+      Due to potential touchscreen hardware flaw, back-powering could happen in
+      suspend if the power supply is on and with active-low reset GPIO asserted.
+      This property is used to avoid the back-powering issue.
+    type: boolean
+
 required:
   - compatible
   - reg
-- 
2.40.1.495.gc816e09b53d-goog

Re: [PATCH v3 1/2] dt-bindings: input: goodix: Add "goodix,no-reset-during-suspend" property

[Jeff LaBundy]

Hi Fei,

On Wed, Apr 26, 2023 at 10:44:21PM +0800, Fei Shao wrote:
> We observed that on Chromebook device Steelix, if Goodix GT7375P
> touchscreen is powered in suspend (because, for example, it connects to
> an always-on regulator) and with the reset GPIO asserted, it will
> introduce about 14mW power leakage.
> 
> To address that, we add this property to skip reset during suspend.
> If it's set, the driver will stop asserting the reset GPIO during
> power-down. Refer to the comments in the driver for details.
> 
> Signed-off-by: Fei Shao <fshao@chromium.org>
> Reviewed-by: Douglas Anderson <dianders@chromium.org>
> Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
> ---

Reviewed-by: Jeff LaBundy <jeff@labundy.com>

> 
> (no changes since v2)
> 
> Changes in v2:
> - Use a more accurate property name and with "goodix," prefix.
> 
>  .../devicetree/bindings/input/goodix,gt7375p.yaml        | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> index ce18d7dadae2..1edad1da1196 100644
> --- a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> +++ b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> @@ -43,6 +43,15 @@ properties:
>        itself as long as it allows the main board to make signals compatible
>        with what the touchscreen is expecting for its IO rails.
>  
> +  goodix,no-reset-during-suspend:
> +    description:
> +      Set this to true to enforce the driver to not assert the reset GPIO
> +      during suspend.
> +      Due to potential touchscreen hardware flaw, back-powering could happen in
> +      suspend if the power supply is on and with active-low reset GPIO asserted.
> +      This property is used to avoid the back-powering issue.
> +    type: boolean
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.40.1.495.gc816e09b53d-goog
> 

Many thanks to you and Doug for the informative discussion.

Kind regards,
Jeff LaBundy