[PATCH v5 2/4] button: add a simple Analog to Digital Converter device based button driver
Marek Szyprowski
m.szyprowski at samsung.com
Thu Feb 4 11:36:45 CET 2021
Hi Simon,
On 01.02.2021 21:38, Simon Glass wrote:
> On Tue, 26 Jan 2021 at 06:03, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>> On 26.01.21 12:25, Marek Szyprowski wrote:
>>> On 26.01.2021 12:10, Heinrich Schuchardt wrote:
>>>> On 1/26/21 10:50 AM, Marek Szyprowski wrote:
>>>>> Add a simple Analog to Digital Converter device based button driver.
>>>>> This
>>>>> driver binds to the 'adc-keys' device tree node.
>>>>>
>>>>> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>>>>> ---
>>>>> drivers/button/Kconfig | 8 ++
>>>>> drivers/button/Makefile | 1 +
>>>>> drivers/button/button-adc.c | 156 ++++++++++++++++++++++++++++++++++++
>>>>> 3 files changed, 165 insertions(+)
>>>>> create mode 100644 drivers/button/button-adc.c
>>>>>
>>>>> diff --git a/drivers/button/Kconfig b/drivers/button/Kconfig
>>>>> index 6b3ec7e55d..6db3c5e93a 100644
>>>>> --- a/drivers/button/Kconfig
>>>>> +++ b/drivers/button/Kconfig
>>>>> @@ -9,6 +9,14 @@ config BUTTON
>>>>> can provide access to board-specific buttons. Use of the
>>>>> device tree
>>>>> for configuration is encouraged.
>>>>>
>>>>> +config BUTTON_ADC
>>>>> + bool "Button adc"
>>>>> + depends on BUTTON
>>>>> + help
>>>>> + Enable support for buttons which are connected to Analog to
>>>>> Digital
>>>>> + Converter device. The ADC driver must use driver model.
>>>>> Buttons are
>>>>> + configured using the device tree.
>>>>> +
>>>>> config BUTTON_GPIO
>>>>> bool "Button gpio"
>>>>> depends on BUTTON
>>>>> diff --git a/drivers/button/Makefile b/drivers/button/Makefile
>>>>> index fcc10ebe8d..bbd18af149 100644
>>>>> --- a/drivers/button/Makefile
>>>>> +++ b/drivers/button/Makefile
>>>>> @@ -3,4 +3,5 @@
>>>>> # Copyright (C) 2020 Philippe Reynes <philippe.reynes at softathome.com>
>>>>>
>>>>> obj-$(CONFIG_BUTTON) += button-uclass.o
>>>>> +obj-$(CONFIG_BUTTON_ADC) += button-adc.o
>>>>> obj-$(CONFIG_BUTTON_GPIO) += button-gpio.o
>>>>> diff --git a/drivers/button/button-adc.c b/drivers/button/button-adc.c
>>>>> new file mode 100644
>>>>> index 0000000000..1901d59a0e
>>>>> --- /dev/null
>>>>> +++ b/drivers/button/button-adc.c
>>>>> @@ -0,0 +1,156 @@
>>>>> +// SPDX-License-Identifier: GPL-2.0
>>>>> +/*
>>>>> + * Copyright (C) 2021 Samsung Electronics Co., Ltd.
>>>>> + * http://www.samsung.com
>>>>> + * Author: Marek Szyprowski <m.szyprowski at samsung.com>
>>>>> + */
>>>>> +
>>>>> +#include <common.h>
>>>>> +#include <adc.h>
>>>>> +#include <button.h>
>>>>> +#include <log.h>
>>>>> +#include <dm.h>
>>>>> +#include <dm/lists.h>
>>>>> +#include <dm/of_access.h>
>>>>> +#include <dm/uclass-internal.h>
>>>>> +
>>>>> +/**
>>>>> + * struct button_adc_priv - private data for button-adc driver.
>>>>> + *
>>>>> + * @adc: Analog to Digital Converter device to which button is
>>>>> connected.
>>>>> + * @channel: channel of the ADC device to probe the button state.
>>>>> + * @min: minimal raw ADC sample value to consider button as pressed.
>>>>> + * @max: maximal raw ADC sample value to consider button as pressed.
>>>>> + */
>>>>> +struct button_adc_priv {
>>>>> + struct udevice *adc;
>>>>> + int channel;
>>>>> + int min;
>>>>> + int max;
>>>>> +};
>>>>> +
>>>>> +static enum button_state_t button_adc_get_state(struct udevice *dev)
>>>>> +{
>>>>> + struct button_adc_priv *priv = dev_get_priv(dev);
>>>>> + unsigned int val;
>>>>> + int ret;
>>>>> +
>>>>> + ret = adc_start_channel(priv->adc, priv->channel);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + ret = adc_channel_data(priv->adc, priv->channel, &val);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + if (ret == 0)
>>>>> + return (val >= priv->min && val < priv->max) ?
>>>>> + BUTTON_ON : BUTTON_OFF;
>>>>> +
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> +static int button_adc_probe(struct udevice *dev)
>>>>> +{
>>>>> + struct button_uc_plat *uc_plat = dev_get_uclass_plat(dev);
>>>>> + struct button_adc_priv *priv = dev_get_priv(dev);
>>>>> + struct ofnode_phandle_args args;
>>>>> + u32 treshold, up_treshold, t;
>>>>> + unsigned int mask;
>>>>> + ofnode node;
>>>>> + int ret, vdd;
>>>>> +
>>>>> + /* Ignore the top-level button node */
>>>>> + if (!uc_plat->label)
>>>>> + return 0;
>>>>> +
>>>>> + ret = dev_read_phandle_with_args(dev->parent, "io-channels",
>>>>> + "#io-channel-cells", 0, 0, &args);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + ret = uclass_get_device_by_ofnode(UCLASS_ADC, args.node,
>>>>> &priv->adc);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + ret = ofnode_read_u32(dev_ofnode(dev->parent),
>>>>> + "keyup-threshold-microvolt", &up_treshold);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + ret = ofnode_read_u32(dev_ofnode(dev), "press-threshold-microvolt",
>>>>> + &treshold);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + dev_for_each_subnode(node, dev->parent) {
>>>>> + ret = ofnode_read_u32(dev_ofnode(dev),
>>>>> + "press-threshold-microvolt", &t);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + if (t > treshold)
>>>>> + up_treshold = t;
>>>> Linux' Documentation/devicetree/bindings/input/adc-keys.txt describes
>>>> that one virtual key is created per sub-node.
>>>>
>>>> If I read your code correctly, this is not what you are implementing.
>>>> Instead you only define a single key per adc-keys node.
>>>>
>>>> Why are your deviating from the bindings document?
>>> No I don't. button_adc_bind() binds to the root node with 'adc-keys'
>>> compatible, while the dev_for_each_subnode() loop instantiates driver
>>> for each subnode, so the button_adc_probe() is called for each defined
>>> key. I've copied this pattern from gpio-keys driver.
>>>
>>> >> ...
>>>
>>> Here is the related code:
>> Thanks for pointing this out.
>>
>> To really test the driver we would need an emulated device on the
>> sandbox where we can set the voltage and see which button is activated.
>>
>> I assume this can be added to test/dm/adc.c.
> Yes please!
Could you give me a bit more hints or point where to start? I've tried
to build sandbox, but it fails for v2021.01 release (I've did make
sandbox_defconfig && make all). I assume I would need to add adc and
adc-keys devices to some sandbox dts and some code triggering and
checking the key values, but that's all I know now.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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