Quoting Dmitry Torokhov (2018-05-31 15:03:36)

On Thu, May 31, 2018 at 1:42 PM, Stephen Boyd [off-list ref] wrote:

quoted

Some wacom w9013 devices have a vddl supply for "low voltage"
requirements. Add support in this driver to turn on this low voltage
supply.

Cc: Benjamin Tissoires <redacted>
Cc: Hans de Goede <redacted>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Dmitry Torokhov <redacted>
Cc: Doug Anderson <dianders@chromium.org>
Cc: <redacted>
Signed-off-by: Stephen Boyd <redacted>
---
 .../bindings/input/hid-over-i2c.txt           |  3 ++-
 drivers/hid/i2c-hid/i2c-hid.c                 | 19 +++++++++++++++++++
 include/linux/platform_data/i2c-hid.h         |  2 ++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/input/hid-over-i2c.txt b/Documentation/devicetree/bindings/input/hid-over-i2c.txt
index 4d3da9d91de4..89e6ab89ba38 100644
--- a/Documentation/devicetree/bindings/input/hid-over-i2c.txt
+++ b/Documentation/devicetree/bindings/input/hid-over-i2c.txt

@@ -26,7 +26,8 @@ device-specific compatible properties, which should be used in addition to the

 - compatible:
   * "wacom,w9013" (Wacom W9013 digitizer). Supports:
-    - vdd-supply
+    - vdd-supply (3.3V)
+    - vddl-supply (1.8V)
     - post-power-on-delay-ms

 - vdd-supply: phandle of the regulator that provides the supply voltage.

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index 6e803f361249..b6f02f98fec6 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c

@@ -1032,12 +1032,29 @@ static int i2c_hid_probe(struct i2c_client *client,
                goto err;
        }

+       ihid->pdata.supply_l = devm_regulator_get(&client->dev, "vddl");
+       if (IS_ERR(ihid->pdata.supply_l)) {
+               ret = PTR_ERR(ihid->pdata.supply_l);
+               if (ret != -EPROBE_DEFER)
+                       dev_err(&client->dev, "Failed to get regulator: %d\n",
+                               ret);
+               goto err;
+       }
+
        ret = regulator_enable(ihid->pdata.supply);
        if (ret < 0) {
                dev_err(&client->dev, "Failed to enable regulator: %d\n",
                        ret);
                goto err;
        }
+
+       ret = regulator_enable(ihid->pdata.supply_l);
+       if (ret < 0) {
+               dev_err(&client->dev, "Failed to enable low regulator: %d\n",
+                       ret);
+               goto err_regulator_l;
+       }
+

Since there don't seem to be any timing constraints between powering
various supplies, maybe use bulk regulator API?

Sure. I left it as is because this driver uses a platform data structure
and converting that to a bulk regulator looked more invasive. I'll
attempt to change it to bulk APIs.