Re: [PATCH V1 2/3] pinctrl: qcom: spmi-gpio: Add dtest route for digital input

Bjorn Andersson
2017-07-12T21:25:02Z

On Mon 12 Jun 23:16 PDT 2017, fenglinw@codeaurora.org wrote:

> From: Fenglin Wu <fenglinw@codeaurora.org>
>
> Add property "qcom,dtest-buffer" to specify which dtest rail to feed
> when the pin is configured as a digital input.
>
> Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>
> ---
> .../devicetree/bindings/pinctrl/qcom,pmic-gpio.txt | 15 ++++++++
> drivers/pinctrl/qcom/pinctrl-spmi-gpio.c | 45 ++++++++++++++++++++++
> include/dt-bindings/pinctrl/qcom,pmic-gpio.h | 6 +++
> 3 files changed, 66 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/pinctrl/qcom,pmic-gpio.txt b/Documentation/devicetree/bindings/pinctrl/qcom,pmic-gpio.txt
> index 1493c0a..521c783 100644
> --- a/Documentation/devicetree/bindings/pinctrl/qcom,pmic-gpio.txt
> +++ b/Documentation/devicetree/bindings/pinctrl/qcom,pmic-gpio.txt
> @@ -195,6 +195,21 @@ to specify in a pin configuration subnode:
> Valid values are 0-3 corresponding to PMIC_GPIO_AOUT_ATESTx
> defined in <dt-bindings/pinctrl/qcom,pmic-gpio.h>.
>
> +- qcom,dtest-buffer:
> + Usage: optional
> + Value type: <u32>
> + Definition: Selects DTEST rail to route to GPIO when it's configured
> + as a digital input.
> + For LV/MV GPIO subtypes, the valid values are 0-3
> + corresponding to PMIC_GPIO_DIN_DTESTx defined in
> + <dt-bindings/pinctrl/qcom,pmic-gpio.h>. Only one
> + DTEST rail can be selected at a time.

As with the analog lines, this is a natural number and I think we should
encode it as such in the DeviceTree.

> + For 4CH/8CH GPIO subtypes, supported values are 1-15.
> + 4 DTEST rails are supported in total and more than 1 DTEST
> + rail can be selected simultaneously. Each bit of the
> + 4 LSBs represent one DTEST rail, such as [3:0] = 0101
> + means both DTEST1 and DTEST3 are selected.

I'm not too keen on encoding this as a bitmask. I would much rather
encode it as multiple values - although that complicates the
implementation.

Or can we just ignore it? (Is the lack of support in the newer chips a
result of no-one using this?)

> +
> Example:
>
> pm8921_gpio: gpio@150 {
> diff --git a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
[..]
> @@ -512,6 +526,13 @@ static int pmic_gpio_config_set(struct pinctrl_dev *pctldev, unsigned int pin,
> return -EINVAL;
> pad->atest = arg;
> break;
> + case PMIC_GPIO_CONF_DTEST_BUFFER:
> + if ((pad->lv_mv_type && arg > PMIC_GPIO_DIN_DTEST4)
> + || (!pad->lv_mv_type && arg >
> + PMIC_GPIO_DIG_IN_DTEST_SEL_MASK))
> + return -EINVAL;
> + pad->dtest_buffer = arg;
> + break;
> default:
> return -EINVAL;
> }
> @@ -544,6 +565,17 @@ static int pmic_gpio_config_set(struct pinctrl_dev *pctldev, unsigned int pin,
> val = PMIC_GPIO_MODE_DIGITAL_OUTPUT;
> }
>

Remember that you're supposed to be able to have two different states
defines, one with dtest-buffer and one without - and switching between
them should enable _and_ disable the dtest buffer.

So you need to detect the absence of qcom,dtest-buffer and you need to
write the register in this case as well. So before looping over all the
config parameters, set pad->dtest_buffer to "disabled" and when you get
here it will either be disabled or have the specified value.

> + if (pad->dtest_buffer != INT_MAX) {
> + val = pad->dtest_buffer;
> + if (pad->lv_mv_type)
> + val |= PMIC_GPIO_LV_MV_DIG_IN_DTEST_EN;
> +

Instead of representing "disabled" as INT_MAX, you could keep track of
it in the same representation as the hardware, i.e. 0 would be disabled.

The additional effort would be in the lv_mv case that you need to mask
in PMIC_GPIO_LV_MV_DIG_IN_DTEST_EN in the few places where you actually
enable dtest buffering.

> + ret = pmic_gpio_write(state, pad,
> + PMIC_GPIO_REG_DIG_IN_CTL, val);
> + if (ret < 0)
> + return ret;
> + }
> +
[..]
> diff --git a/include/dt-bindings/pinctrl/qcom,pmic-gpio.h b/include/dt-bindings/pinctrl/qcom,pmic-gpio.h
> index 85d8809..21738ed 100644
> --- a/include/dt-bindings/pinctrl/qcom,pmic-gpio.h
> +++ b/include/dt-bindings/pinctrl/qcom,pmic-gpio.h
> @@ -99,6 +99,12 @@
> #define PMIC_GPIO_AOUT_ATEST3 2
> #define PMIC_GPIO_AOUT_ATEST4 3
>
> +/* DTEST buffer for digital input mode */
> +#define PMIC_GPIO_DIN_DTEST1 0
> +#define PMIC_GPIO_DIN_DTEST2 1
> +#define PMIC_GPIO_DIN_DTEST3 2
> +#define PMIC_GPIO_DIN_DTEST4 3
> +

Please drop these defines.

Regards,
Bjorn