Re: [PATCH] Input: edt-ft5x06 - Switch to newer gpio framework

Dmitry Torokhov
2015-08-25T00:17:55Z

On Mon, Aug 24, 2015 at 05:16:15PM -0500, Franklin S Cooper Jr. wrote:
>
>
> On 08/24/2015 03:56 PM, Dmitry Torokhov wrote:
> > On Mon, Aug 24, 2015 at 03:23:43PM -0500, Franklin S Cooper Jr. wrote:
> >>
> >> On 08/24/2015 03:16 PM, Franklin S Cooper Jr. wrote:
> >>> On 08/24/2015 03:01 PM, Dmitry Torokhov wrote:
> >>>> On Mon, Aug 24, 2015 at 02:48:36PM -0500, Franklin S Cooper Jr. wrote:
> >>>>> On 08/24/2015 02:41 PM, Dmitry Torokhov wrote:
> >>>>>> On Fri, Aug 21, 2015 at 02:08:32PM -0500, Franklin S Cooper Jr wrote:
> >>>>>>> The current/old gpio framework used doesn't properly listen to
> >>>>>>> ACTIVE_LOW and ACTIVE_HIGH flags. The newer gpio framework takes into
> >>>>>>> account these flags when setting gpio values.
> >>>>>>>
> >>>>>>> Also use gpiod_set_value_cansleep since wake and reset pins can be
> >>>>>>> provided by bus based io expanders.
> >>>>>>>
> >>>>>>> Signed-off-by: Franklin S Cooper Jr <fcooper-l0cyMroinI0@public.gmane.org>
> >>>>>>> ---
> >>>>>>> .../bindings/input/touchscreen/edt-ft5x06.txt | 4 +-
> >>>>>>> drivers/input/touchscreen/edt-ft5x06.c | 115 +++++++--------------
> >>>>>>> include/linux/input/edt-ft5x06.h | 4 +-
> >>>>>>> 3 files changed, 43 insertions(+), 80 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt b/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt
> >>>>>>> index 76db967..9330d4d 100644
> >>>>>>> --- a/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt
> >>>>>>> +++ b/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.txt
> >>>>>>> @@ -50,6 +50,6 @@ Example:
> >>>>>>> pinctrl-0 = <&edt_ft5x06_pins>;
> >>>>>>> interrupt-parent = <&gpio2>;
> >>>>>>> interrupts = <5 0>;
> >>>>>>> - reset-gpios = <&gpio2 6 1>;
> >>>>>>> - wake-gpios = <&gpio4 9 0>;
> >>>>>>> + reset-gpios = <&gpio2 6 GPIO_ACTIVE_LOW>;
> >>>>>>> + wake-gpios = <&gpio4 9 GPIO_ACTIVE_HIGH>;
> >>>>>>> };
> >>>>>>> diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
> >>>>>>> index 394b1de..6b128b3 100644
> >>>>>>> --- a/drivers/input/touchscreen/edt-ft5x06.c
> >>>>>>> +++ b/drivers/input/touchscreen/edt-ft5x06.c
> >>>>>>> @@ -91,9 +91,9 @@ struct edt_ft5x06_ts_data {
> >>>>>>> u16 num_x;
> >>>>>>> u16 num_y;
> >>>>>>>
> >>>>>>> - int reset_pin;
> >>>>>>> - int irq_pin;
> >>>>>>> - int wake_pin;
> >>>>>>> + struct gpio_desc *reset_pin;
> >>>>>>> + struct gpio_desc *wake_pin;
> >>>>>>> + struct gpio_desc *irq_pin;
> >>>>>>>
> >>>>>>> #if defined(CONFIG_DEBUG_FS)
> >>>>>>> struct dentry *debug_dir;
> >>>>>>> @@ -755,36 +755,14 @@ edt_ft5x06_ts_teardown_debugfs(struct edt_ft5x06_ts_data *tsdata)
> >>>>>>> static int edt_ft5x06_ts_reset(struct i2c_client *client,
> >>>>>>> struct edt_ft5x06_ts_data *tsdata)
> >>>>>>> {
> >>>>>>> - int error;
> >>>>>>> -
> >>>>>>> - if (gpio_is_valid(tsdata->wake_pin)) {
> >>>>>>> - error = devm_gpio_request_one(&client->dev,
> >>>>>>> - tsdata->wake_pin, GPIOF_OUT_INIT_LOW,
> >>>>>>> - "edt-ft5x06 wake");
> >>>>>>> - if (error) {
> >>>>>>> - dev_err(&client->dev,
> >>>>>>> - "Failed to request GPIO %d as wake pin, error %d\n",
> >>>>>>> - tsdata->wake_pin, error);
> >>>>>>> - return error;
> >>>>>>> - }
> >>>>>>> -
> >>>>>>> + if (tsdata->wake_pin) {
> >>>>>>> msleep(5);
> >>>>>>> - gpio_set_value(tsdata->wake_pin, 1);
> >>>>>>> + gpiod_set_value_cansleep(tsdata->wake_pin, 1);
> >>>>>>> }
> >>>>>>> - if (gpio_is_valid(tsdata->reset_pin)) {
> >>>>>>> - /* this pulls reset down, enabling the low active reset */
> >>>>>>> - error = devm_gpio_request_one(&client->dev,
> >>>>>>> - tsdata->reset_pin, GPIOF_OUT_INIT_LOW,
> >>>>>>> - "edt-ft5x06 reset");
> >>>>>>> - if (error) {
> >>>>>>> - dev_err(&client->dev,
> >>>>>>> - "Failed to request GPIO %d as reset pin, error %d\n",
> >>>>>>> - tsdata->reset_pin, error);
> >>>>>>> - return error;
> >>>>>>> - }
> >>>>>>>
> >>>>>>> + if (tsdata->reset_pin) {
> >>>>>>> msleep(5);
> >>>>>>> - gpio_set_value(tsdata->reset_pin, 1);
> >>>>>>> + gpiod_set_value_cansleep(tsdata->reset_pin, 1);
> >>>>>> So this leaves the reset pin active. How exactly was this tested?
> >>>>> Normally if the output gpio connected to the reset pin is ACTIVE_HIGH then this will take the tsc out of reset since
> >>>>> the reset pin is active low. However, I have a board that has an inverter between the gpio and reset pin. So if I leave
> >>>>> the gpio as ACTIVE_HIGH then the inverter would cause the reset pin to go low which will keep it in reset. So instead
> >>>>> I set the gpio to ACTIVE_LOW which gives me the expected result.
> >>>> I do not really care about particular board. Assuming that polarity of
> >>>> the GPIO in DTS is specified correctly the effect of:
> >>>>
> >>>> gpiod_set_value_cansleep(tsdata->reset_pin, 1);
> >>>>
> >>>> is reset pin being _active_, i.e. the chip is staying in reset state.
> >>> Setting the reset pin to 1/high will take the tsc out of reset. Setting the pin to 0/low will put the tsc into reset mode.
> > It seems you are not quite getting gpiod API. Consider:
> >
> > For gpios described as GPIO_ACTIVE_LOW:
> >
> > gpiod_set_value_cansleep(gpio, 1) => GPIO is LOW
> > gpiod_set_value_cansleep(gpio, 0) => GPIO is HIGH
> >
> > For gpios described as GPIO_ACTIVE_HIGH:
> >
> > gpiod_set_value_cansleep(gpio, 1) => GPIO is HIGH
> > gpiod_set_value_cansleep(gpio, 0) => GPIO is LOW
> >
> > IOW with gpiod API 1 means logical active and can be either HIGH or LOW,
> > depending on GPIO definition in DTS.
> >
> >>>> By the way, both reset and wake pins are active low according to the
> >>>> data sheet I found.
> >>> Your right. Reset and wake are both active low. However, that part of the code is trying to get the tsc out of reset which is
> >>> why its setting the value to 1. Setting the pin to 1 was being done even before my patch.
> >>>
> >>> What has changed was removing the below line which puts the tsc in reset.
> >>>
> >>> error = devm_gpio_request_one(&client->dev, tsdata->reset_pin, GPIOF_OUT_INIT_LOW,"edt-ft5x06 reset");
> >>>
> >>> However, the above line isn't needed since when I request the gpio I already configured it as an output
> >>> with a default value of 0.
> > So the old sequence resulted in GPIO going XXX->0->1 which brought the
> > chip into reset and out of it. With the sequence you have, assuming
> > that the GPIO is described as GPIO_ACTIVE_LOW (to match data sheet),
> I'm not setting the GPIO_ACTIVE_LOW to match the datasheet. I'm setting it to ACTIVE_LOW because
> of the inverter that is between the gpio and reset pin makes it "appear" as if the gpio is ACTIVE_LOW.

If the "normal" behavior (according to the data sheet) is active low and
you have an invertor, then your DTS should be GPIO_ACTIVE_HIGH. And
people with hardware that does not have invertor will use
GPIO_ACTIVE_LOW. And the driver should work with both settings.

> > we'll be getting XXX->1->0:
> >
> > devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_LOW) =>
> > GPIO is *HIGH*
> >
> > gpiod_set_value_cansleep(gpio, 1) => GPIO is *LOW*
> So everything you stated is exactly what I wanted and expected when you take into account the inverter will invert the gpio signal before
> it reaches the reset pin.

I do not want to take into account invertor, that is what DTS polarity
flag for. Regular setup for this touchscreen - GPIO_ACTIVE_LOW, setup
with invertor - GPIO_ACTIVE_HIGH. From the driver perspective you should
be leaving the power on/reset function with reset and wake GPIOs
*inactive* (as in gpiod_set_value_cansleep(gpio, 0)).

Thanks.

--
Dmitry