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Date: Wed, 9 Jul 2014 10:53:35 +0200
Message-ID: <CACRpkdZ2hekBGe1-9GV-amqi50heghWhXJ9raW7P_Nif_Ci88g@mail.gmail.com>
Subject: Re: [PATCH 2/3] pinctrl: Device tree bindings for Qualcomm pm8xxx
 gpio block
From: Linus Walleij <linus.walleij@linaro.org>
To: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Cc: Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>
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On Tue, Jul 8, 2014 at 3:26 AM, Bjorn Andersson
<bjorn.andersson@sonymobile.com> wrote:

> This introduced the device tree bindings for the gpio block found in
> pm8018, pm8038, pm8058, pm8917 and pm8921 pmics from Qualcomm.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
(...)
> +- interrupts:
> +       Usage: required
> +       Value type: <prop-encoded-array>
> +       Definition: Must contain an array of encoded interrupt specifiers for
> +                   each available gpio

So each GPIO has its own interrupt line looped back from the PMIC
and into some other SoC or so handling the actual interrupt?
This seems expensive? (Albeit efficient and fast.)

(...)
> +Please refer to pinctrl-bindings.txt in this directory for details of the
> +common pinctrl bindings used by client devices, including the meaning of the
> +phrase "pin configuration node".
> +
> +The pin configuration nodes act as a container for an abitrary number of
> +subnodes. Each of these subnodes represents some desired configuration for a
> +pin or a list of pins. This configuration can include the
> +mux function to select on those pin(s), and various pin configuration
> +parameters, s listed below.

*is* listed below?

> +The following generic properties as defined in pinctrl-bindings.txt are valid
> +to specify in a pin configuration subnode:
> +
> +- pins:
> +       Usage: required
> +       Value type: <string-array>
> +       Definition: List of gpio pins affected by the properties specified in
> +                   this subnode.  Valid pins are:
> +                       gpio1-gpio6 for pm8018
> +                       gpio1-gpio12 for pm8038
> +                       gpio1-gpio40 for pm8058
> +                       gpio1-gpio38 for pm8917
> +                       gpio1-gpio44 for pm8921

I usually name pins with CAPITAL LETTERS so would be
"GPIO1", "GPIO2" etc, lowercase may be confusing as these are
names not functions or groups.

> +- function:
> +       Usage: optional
> +       Value type: <string>
> +       Definition: Specify the alternative function to be configured for the
> +                   specified pins.  Valid values are:
> +                       "normal",
> +                       "paired",
> +                       "func1",
> +                       "func2",
> +                       "dtest1",
> +                       "dtest2",
> +                       "dtest3",
> +                       "dtest4"

These are a bit ambigous, why doesn't the driver present functions that
are more specific than "func1", "func2"? Or "dtest1"?

I guess the following just redefines or extends the generic pinconf
bindings (which is fully OK).

> +- bias-disable:
> +       Usage: optional
> +       Value type: <none>

Isn't the type simply bool?

> +- bias-pull-down:
> +       Usage: optional
> +       Value type: <none>

bool?

> +- bias-pull-up:
> +       Usage: optional
> +       Value type: <u32> (optional)
> +       Definition: The specified pins should be configued as pull up. An
> +                   optional argument can be used to configure the strength.
> +                   Valid values are; as defined in
> +                   <dt-bindings/pinctrl/qcom,pm8xxx-gpio.h>:
> +                   1: 30uA                     (PM8XXX_GPIO_PULL_UP_30)
> +                   2: 1.5uA                    (PM8XXX_GPIO_PULL_UP_1P5)
> +                   3: 31.5uA                   (PM8XXX_GPIO_PULL_UP_31P5)
> +                   4: 1.5uA + 30uA boost       (PM8XXX_GPIO_PULL_UP_1P5_30)

Hm, I don't know of the internal kernel API or so, but I'm thinking that
for the DT bindings, this definition should be generic in
Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
and put in SI units like uA.

So I would prefer:

bias-pull-up = <30>;

for 30 uA. Maybe we want nA even? I'm uncertain about the proper granularity
here :-/

Magic enumerators 1,2,3,4 doesn't seem so good, that seems more like it's
trying to match the magic value that is to be poked into a register or
something like that.

> +- bias-high-impedance:
> +       Usage: optional
> +       Value type: <none>

bool

> +- input-enable:
> +       Usage: optional
> +       Value type: <none>

bool

> +- output-high:
> +       Usage: optional
> +       Value type: <none>

bool

> +- output-low:
> +       Usage: optional
> +       Value type: <none>

bool

> +- power-source:
> +       Usage: optional
> +       Value type: <u32>
> +       Definition: Selects the power source for the specified pins. Valid
> +                   power sources are, as defined in
> +                   <dt-bindings/pinctrl/qcom,pm8xxx-gpio.h>:
> +                       0: bb (PM8XXX_GPIO_VIN_BB)
> +                               valid for pm8038, pm8058, pm8917, pm8921
> +                       1: ldo2 (PM8XXX_GPIO_VIN_L2)
> +                               valid for pm8018, pm8038, pm8917,pm8921
> +                       2: ldo3 (PM8XXX_GPIO_VIN_L3)
> +                               valid for pm8038, pm8058, pm8917, pm8921
> +                       3: ldo4 (PM8XXX_GPIO_VIN_L4)
> +                               valid for pm8018, pm8917, pm8921
> +                       4: ldo5 (PM8XXX_GPIO_VIN_L5)
> +                               valid for pm8018, pm8058
> +                       5: ldo6 (PM8XXX_GPIO_VIN_L6)
> +                               valid for pm8018, pm8058
> +                       6: ldo7 (PM8XXX_GPIO_VIN_L7)
> +                               valid for pm8058
> +                       7: ldo8 (PM8XXX_GPIO_VIN_L8)
> +                               valid for pm8018
> +                       8: ldo11 (PM8XXX_GPIO_VIN_L11)
> +                               valid for pm8038
> +                       9: ldo14 (PM8XXX_GPIO_VIN_L14)
> +                               valid for pm8018
> +                       10: ldo15 (PM8XXX_GPIO_VIN_L15)
> +                               valid for pm8038, pm8917, pm8921
> +                       11: ldo17 (PM8XXX_GPIO_VIN_L17)
> +                               valid for pm8038, pm8917, pm8921
> +                       12: smps3 (PM8XXX_GPIO_VIN_S3)
> +                               valid for pm8018, pm8058
> +                       13: smps4 (PM8XXX_GPIO_VIN_S4)
> +                               valid for pm8921
> +                       14: vph (PM8XXX_GPIO_VIN_VPH)
> +                               valid for pm8018, pm8038, pm8058, pm8917 pm8921

These are more apropriate to have in custom format selectors
I think, so this is OK.

> +- drive-strength:
> +       Usage: optional
> +       Value type: <u32>
> +       Definition: Selects the drive strength for the specified pins. Value
> +                   drive strengths are:
> +                       0: no   (PM8XXX_GPIO_STRENGTH_NO)
> +                       1: high (PM8XXX_GPIO_STRENGTH_HIGH)
> +                       2: medium       (PM8XXX_GPIO_STRENGTH_MED)
> +                       3: low  (PM8XXX_GPIO_STRENGTH_LOW)

I would really prefer to have these in mA, because the genric pinconf
bindings say they should be! SI units are so much more understandable.

> +- drive-push-pull:
> +       Usage: optional
> +       Value type: <none>

bool

> +- drive-open-drain:
> +       Usage: optional
> +       Value type: <none>

bool

> +Example:
> +
> +       pm8921_gpio: gpio@150 {
> +               compatible = "qcom,pm8921-gpio";
> +               reg = <0x150>;
> +               interrupts = <192 1>, <193 1>, <194 1>,
> +                            <195 1>, <196 1>, <197 1>,
> +                            <198 1>, <199 1>, <200 1>,
> +                            <201 1>, <202 1>, <203 1>,
> +                            <204 1>, <205 1>, <206 1>,
> +                            <207 1>, <208 1>, <209 1>,
> +                            <210 1>, <211 1>, <212 1>,
> +                            <213 1>, <214 1>, <215 1>,
> +                            <216 1>, <217 1>, <218 1>,
> +                            <219 1>, <220 1>, <221 1>,
> +                            <222 1>, <223 1>, <224 1>,
> +                            <225 1>, <226 1>, <227 1>,
> +                            <228 1>, <229 1>, <230 1>,
> +                            <231 1>, <232 1>, <233 1>,
> +                            <234 1>, <235 1>;


So this looks a bit weird. But if I just get to understand the hardware
I guess it won't anymore.

So there is an interrupt parent to which the IRQ lines from the PMIC
are routed back through external lines to IRQ offsets 192 thru 235?

Yours,
Linus Walleij
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