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

From: Fenglin Wu
Date: Thu Jul 13 2017 - 01:27:17 EST

On 7/13/2017 5:24 AM, Bjorn Andersson wrote:
On Mon 12 Jun 23:16 PDT 2017, fenglinw@xxxxxxxxxxxxxx wrote:

From: Fenglin Wu <fenglinw@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
.../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

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

I am not quite sure if any real cases would route multiple DTEST line to
single GPIO, but the register mapping uses the bit mask for 4CH/8CH
subtypes and I think we should support it accordingly. Even if I drop
the support, we still have the difference of the register mapping on the
dtest selection between MV/LV subtypes and legacy 4CH/8CH subtypes,
which means we need a place to unify the dtest definition. I put the
complication here in dtsi which the end user would choose the right
value according to the hardware. I am also fine with putting the
complication in C code, but that would drop the supporting of multiple
DTEST lines selection for 4CH/8CH subtype.

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;
+ if ((pad->lv_mv_type && arg > PMIC_GPIO_DIN_DTEST4)
+ || (!pad->lv_mv_type && arg >
+ return -EINVAL;
+ pad->dtest_buffer = arg;
+ break;
return -EINVAL;
@@ -544,6 +565,17 @@ static int pmic_gpio_config_set(struct pinctrl_dev *pctldev, unsigned int pin,

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)

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.

Thanks for your suggestion, I got the issue here. PMIC_GPIO_LV_MV_DIG_IN_DTEST_EN need to be unmasked in the case of dtest
If we decided to drop the multiple dtest line selection (actually I am fine with it) and unify the dtest lines values to 1~4 from dtsi, I am Ok with the suggestion of using 0 to represent "disabled".

+ ret = pmic_gpio_write(state, pad,
+ 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 @@
+/* DTEST buffer for digital input mode */

Please drop these defines.

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