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Date:   Sun, 12 Jul 2020 14:19:46 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Artur Rojek <contact@artur-rojek.eu>
Cc:     Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Paul Cercueil <paul@crapouillou.net>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Heiko Stuebner <heiko@sntech.de>,
        Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>,
        devicetree@vger.kernel.org, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 6/6] IIO: Ingenic JZ47xx: Add touchscreen mode.
Message-ID: <20200712141946.7d8f802f@archlinux>
In-Reply-To: <20200709152200.10039-7-contact@artur-rojek.eu>
References: <20200709152200.10039-1-contact@artur-rojek.eu>
        <20200709152200.10039-7-contact@artur-rojek.eu>
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On Thu,  9 Jul 2020 17:22:00 +0200
Artur Rojek <contact@artur-rojek.eu> wrote:

> The SADC component in JZ47xx SoCs provides support for touchscreen
> operations (pen position and pen down pressure) in single-ended and
> differential modes.
> 
> The touchscreen component of SADC takes a significant time to stabilize
> after first receiving the clock and a delay of 50ms has been empirically
> proven to be a safe value before data sampling can begin.
> 
> Of the known hardware to use this controller, GCW Zero and Anbernic RG-350
> utilize the touchscreen mode by having their joystick(s) attached to the
> X/Y positive/negative input pins.
> 
> JZ4770 and later SoCs introduce a low-level command feature. With it, up
> to 32 commands can be programmed, each one corresponding to a sampling
> job. It allows to change the low-voltage reference, the high-voltage
> reference, have them connected to VCC, GND, or one of the X-/X+ or Y-/Y+
> pins.
> 
> This patch introduces support for 6 stream-capable channels:
> - channel #0 samples X+/GND
> - channel #1 samples Y+/GND
> - channel #2 samples X-/GND
> - channel #3 samples Y-/GND
> - channel #4 samples X+/X-
> - channel #5 samples Y+/Y-

The one thing I noticed on this read was that we are slightly stretching
the normal IIO channel definitions.  The claim is that each of these channels
is a POSITIONREALTIVE channel, whereas that isn't really true.  They are
related to the position, but as I understand it not directly measuring it
(particularly X+ - X-) which is pretty much a reference voltage (I think!)

We might be better off just describing these as voltage channels, with
4 and 5 described as differential voltage channels.  The problem there
being that it doesn't describe the fact that the measurements are with
particular voltages also being applied to the touch screen.

Perhaps we are best off just leaving it as you have it and being a bit
'odd'.  What do you think?  Having written this down I think perhaps leaving
it alone is the best plan :(

Otherwise this all looks fine to me.

Thanks,

Jonathan

> 
> Being able to sample X-/GND and Y-/GND is useful on some devices, where
> one joystick is connected to the X+/Y+ pins, and a second joystick is
> connected to the X-/Y- pins.
> 
> All the boards which probe this driver have the interrupt provided from
> Device Tree, with no need to handle a case where the IRQ was not provided.
> 
> Co-developed-by: Paul Cercueil <paul@crapouillou.net>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
> ---
> 
>  Changes:
> 
>  v2: - improve description of the touchscreen mode,
>      - get rid of the unneeded kfifo,
>      - drop IIO_BUFFER_CB from Kconfig,
>      - remove extended names from the touchscreen channels
> 
>  v3: remove unneeded `linux/iio/kfifo_buf.h` include
> 
>  v4: clarify irq provider source in the patch description
> 
>  v5: no change
> 
>  v6: - correct the spelling of Device Tree and IRQ in commit message
>      - don't omit trailing commas from initializer lists
>      - error check `clk_enable`
>      - remove redundant `dev_err` from `platform_get_irq` error check
> 
>  v7: no change
> 
>  v8: add support for ADCMD low-level command feature
> 
>  drivers/iio/adc/Kconfig       |   1 +
>  drivers/iio/adc/ingenic-adc.c | 250 +++++++++++++++++++++++++++++++++-
>  2 files changed, 249 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index ff3569635ce0..5b57437cef75 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -500,6 +500,7 @@ config INA2XX_ADC
>  config INGENIC_ADC
>  	tristate "Ingenic JZ47xx SoCs ADC driver"
>  	depends on MIPS || COMPILE_TEST
> +	select IIO_BUFFER
>  	help
>  	  Say yes here to build support for the Ingenic JZ47xx SoCs ADC unit.
>  
> diff --git a/drivers/iio/adc/ingenic-adc.c b/drivers/iio/adc/ingenic-adc.c
> index 0233a9055c86..976aea46fede 100644
> --- a/drivers/iio/adc/ingenic-adc.c
> +++ b/drivers/iio/adc/ingenic-adc.c
> @@ -8,7 +8,9 @@
>  
>  #include <dt-bindings/iio/adc/ingenic,adc.h>
>  #include <linux/clk.h>
> +#include <linux/iio/buffer.h>
>  #include <linux/iio/iio.h>
> +#include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/iopoll.h>
>  #include <linux/kernel.h>
> @@ -20,19 +22,46 @@
>  #define JZ_ADC_REG_CFG			0x04
>  #define JZ_ADC_REG_CTRL			0x08
>  #define JZ_ADC_REG_STATUS		0x0c
> +#define JZ_ADC_REG_ADSAME		0x10
> +#define JZ_ADC_REG_ADWAIT		0x14
>  #define JZ_ADC_REG_ADTCH		0x18
>  #define JZ_ADC_REG_ADBDAT		0x1c
>  #define JZ_ADC_REG_ADSDAT		0x20
> +#define JZ_ADC_REG_ADCMD		0x24
>  #define JZ_ADC_REG_ADCLK		0x28
>  
>  #define JZ_ADC_REG_ENABLE_PD		BIT(7)
>  #define JZ_ADC_REG_CFG_AUX_MD		(BIT(0) | BIT(1))
>  #define JZ_ADC_REG_CFG_BAT_MD		BIT(4)
> +#define JZ_ADC_REG_CFG_SAMPLE_NUM(n)	((n) << 10)
> +#define JZ_ADC_REG_CFG_PULL_UP(n)	((n) << 16)
> +#define JZ_ADC_REG_CFG_CMD_SEL		BIT(22)
> +#define JZ_ADC_REG_CFG_TOUCH_OPS_MASK	(BIT(31) | GENMASK(23, 10))
>  #define JZ_ADC_REG_ADCLK_CLKDIV_LSB	0
>  #define JZ4725B_ADC_REG_ADCLK_CLKDIV10US_LSB	16
>  #define JZ4770_ADC_REG_ADCLK_CLKDIV10US_LSB	8
>  #define JZ4770_ADC_REG_ADCLK_CLKDIVMS_LSB	16
>  
> +#define JZ_ADC_REG_ADCMD_YNADC		BIT(7)
> +#define JZ_ADC_REG_ADCMD_YPADC		BIT(8)
> +#define JZ_ADC_REG_ADCMD_XNADC		BIT(9)
> +#define JZ_ADC_REG_ADCMD_XPADC		BIT(10)
> +#define JZ_ADC_REG_ADCMD_VREFPYP	BIT(11)
> +#define JZ_ADC_REG_ADCMD_VREFPXP	BIT(12)
> +#define JZ_ADC_REG_ADCMD_VREFPXN	BIT(13)
> +#define JZ_ADC_REG_ADCMD_VREFPAUX	BIT(14)
> +#define JZ_ADC_REG_ADCMD_VREFPVDD33	BIT(15)
> +#define JZ_ADC_REG_ADCMD_VREFNYN	BIT(16)
> +#define JZ_ADC_REG_ADCMD_VREFNXP	BIT(17)
> +#define JZ_ADC_REG_ADCMD_VREFNXN	BIT(18)
> +#define JZ_ADC_REG_ADCMD_VREFAUX	BIT(19)
> +#define JZ_ADC_REG_ADCMD_YNGRU		BIT(20)
> +#define JZ_ADC_REG_ADCMD_XNGRU		BIT(21)
> +#define JZ_ADC_REG_ADCMD_XPGRU		BIT(22)
> +#define JZ_ADC_REG_ADCMD_YPSUP		BIT(23)
> +#define JZ_ADC_REG_ADCMD_XNSUP		BIT(24)
> +#define JZ_ADC_REG_ADCMD_XPSUP		BIT(25)
> +
>  #define JZ_ADC_AUX_VREF				3300
>  #define JZ_ADC_AUX_VREF_BITS			12
>  #define JZ_ADC_BATTERY_LOW_VREF			2500
> @@ -44,6 +73,14 @@
>  #define JZ4770_ADC_BATTERY_VREF			6600
>  #define JZ4770_ADC_BATTERY_VREF_BITS		12
>  
> +#define JZ_ADC_IRQ_AUX			BIT(0)
> +#define JZ_ADC_IRQ_BATTERY		BIT(1)
> +#define JZ_ADC_IRQ_TOUCH		BIT(2)
> +#define JZ_ADC_IRQ_PEN_DOWN		BIT(3)
> +#define JZ_ADC_IRQ_PEN_UP		BIT(4)
> +#define JZ_ADC_IRQ_PEN_DOWN_SLEEP	BIT(5)
> +#define JZ_ADC_IRQ_SLEEP		BIT(7)
> +
>  struct ingenic_adc;
>  
>  struct ingenic_adc_soc_data {
> @@ -69,6 +106,61 @@ struct ingenic_adc {
>  	bool low_vref_mode;
>  };
>  
> +static void ingenic_adc_set_adcmd(struct iio_dev *iio_dev, unsigned long mask)
> +{
> +	struct ingenic_adc *adc = iio_priv(iio_dev);
> +
> +	mutex_lock(&adc->lock);
> +
> +	/* Init ADCMD */
> +	readl(adc->base + JZ_ADC_REG_ADCMD);
> +
> +	if (mask & 0x3) {
> +		/* Second channel (INGENIC_ADC_TOUCH_YP): sample YP vs. GND */
> +		writel(JZ_ADC_REG_ADCMD_XNGRU
> +		       | JZ_ADC_REG_ADCMD_VREFNXN | JZ_ADC_REG_ADCMD_VREFPVDD33
> +		       | JZ_ADC_REG_ADCMD_YPADC,
> +		       adc->base + JZ_ADC_REG_ADCMD);
> +
> +		/* First channel (INGENIC_ADC_TOUCH_XP): sample XP vs. GND */
> +		writel(JZ_ADC_REG_ADCMD_YNGRU
> +		       | JZ_ADC_REG_ADCMD_VREFNYN | JZ_ADC_REG_ADCMD_VREFPVDD33
> +		       | JZ_ADC_REG_ADCMD_XPADC,
> +		       adc->base + JZ_ADC_REG_ADCMD);
> +	}
> +
> +	if (mask & 0xc) {
> +		/* Fourth channel (INGENIC_ADC_TOUCH_YN): sample YN vs. GND */
> +		writel(JZ_ADC_REG_ADCMD_XNGRU
> +		       | JZ_ADC_REG_ADCMD_VREFNXN | JZ_ADC_REG_ADCMD_VREFPVDD33
> +		       | JZ_ADC_REG_ADCMD_YNADC,
> +		       adc->base + JZ_ADC_REG_ADCMD);
> +
> +		/* Third channel (INGENIC_ADC_TOUCH_XN): sample XN vs. GND */
> +		writel(JZ_ADC_REG_ADCMD_YNGRU
> +		       | JZ_ADC_REG_ADCMD_VREFNYN | JZ_ADC_REG_ADCMD_VREFPVDD33
> +		       | JZ_ADC_REG_ADCMD_XNADC,
> +		       adc->base + JZ_ADC_REG_ADCMD);
> +	}
> +
> +	if (mask & 0x30) {
> +		/* Sixth channel (INGENIC_ADC_TOUCH_YD): sample YP vs. YN */
> +		writel(JZ_ADC_REG_ADCMD_VREFNYN | JZ_ADC_REG_ADCMD_VREFPVDD33
> +		       | JZ_ADC_REG_ADCMD_YPADC,
> +		       adc->base + JZ_ADC_REG_ADCMD);
> +
> +		/* Fifth channel (INGENIC_ADC_TOUCH_XD): sample XP vs. XN */
> +		writel(JZ_ADC_REG_ADCMD_VREFNXN | JZ_ADC_REG_ADCMD_VREFPVDD33
> +		       | JZ_ADC_REG_ADCMD_XPADC,
> +		       adc->base + JZ_ADC_REG_ADCMD);
> +	}
> +
> +	/* We're done */
> +	writel(0, adc->base + JZ_ADC_REG_ADCMD);
> +
> +	mutex_unlock(&adc->lock);
> +}
> +
>  static void ingenic_adc_set_config(struct ingenic_adc *adc,
>  				   uint32_t mask,
>  				   uint32_t val)
> @@ -288,6 +380,72 @@ static const struct iio_chan_spec jz4740_channels[] = {
>  };
>  
>  static const struct iio_chan_spec jz4770_channels[] = {
> +	{
> +		.type = IIO_POSITIONRELATIVE,
> +		.indexed = 1,
> +		.channel = INGENIC_ADC_TOUCH_XP,

Ah. sorry. I should have noticed this much earlier.

These aren't position channels as such.  They are channels
that are then processed into position in combination.  

Problem is I'm not sure how we 'should' describe then.

Perhaps this is the best we can do.

> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
> +	{
> +		.type = IIO_POSITIONRELATIVE,
> +		.indexed = 1,
> +		.channel = INGENIC_ADC_TOUCH_YP,
> +		.scan_index = 1,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
> +	{
> +		.type = IIO_POSITIONRELATIVE,
> +		.indexed = 1,
> +		.channel = INGENIC_ADC_TOUCH_XN,
> +		.scan_index = 2,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
> +	{
> +		.type = IIO_POSITIONRELATIVE,
> +		.indexed = 1,
> +		.channel = INGENIC_ADC_TOUCH_YN,
> +		.scan_index = 3,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
> +	{
> +		.type = IIO_POSITIONRELATIVE,
> +		.indexed = 1,
> +		.channel = INGENIC_ADC_TOUCH_XD,
> +		.scan_index = 4,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
> +	{
> +		.type = IIO_POSITIONRELATIVE,
> +		.indexed = 1,
> +		.channel = INGENIC_ADC_TOUCH_YD,
> +		.scan_index = 5,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
>  	{
>  		.extend_name = "aux",
>  		.type = IIO_VOLTAGE,
> @@ -490,13 +648,89 @@ static const struct iio_info ingenic_adc_info = {
>  	.of_xlate = ingenic_adc_of_xlate,
>  };
>  
> +static int ingenic_adc_buffer_enable(struct iio_dev *iio_dev)
> +{
> +	struct ingenic_adc *adc = iio_priv(iio_dev);
> +	int ret;
> +
> +	ret = clk_enable(adc->clk);
> +	if (ret) {
> +		dev_err(iio_dev->dev.parent, "Failed to enable clock: %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	/* It takes significant time for the touchscreen hw to stabilize. */
> +	msleep(50);
> +	ingenic_adc_set_config(adc, JZ_ADC_REG_CFG_TOUCH_OPS_MASK,
> +			       JZ_ADC_REG_CFG_SAMPLE_NUM(4) |
> +			       JZ_ADC_REG_CFG_PULL_UP(4));
> +
> +	writew(80, adc->base + JZ_ADC_REG_ADWAIT);
> +	writew(2, adc->base + JZ_ADC_REG_ADSAME);
> +	writeb((u8)~JZ_ADC_IRQ_TOUCH, adc->base + JZ_ADC_REG_CTRL);
> +	writel(0, adc->base + JZ_ADC_REG_ADTCH);
> +
> +	ingenic_adc_set_config(adc, JZ_ADC_REG_CFG_CMD_SEL,
> +			       JZ_ADC_REG_CFG_CMD_SEL);
> +	ingenic_adc_set_adcmd(iio_dev, iio_dev->active_scan_mask[0]);
> +
> +	ingenic_adc_enable(adc, 2, true);
> +
> +	return 0;
> +}
> +
> +static int ingenic_adc_buffer_disable(struct iio_dev *iio_dev)
> +{
> +	struct ingenic_adc *adc = iio_priv(iio_dev);
> +
> +	ingenic_adc_enable(adc, 2, false);
> +
> +	ingenic_adc_set_config(adc, JZ_ADC_REG_CFG_CMD_SEL, 0);
> +
> +	writeb(0xff, adc->base + JZ_ADC_REG_CTRL);
> +	writeb(0xff, adc->base + JZ_ADC_REG_STATUS);
> +	ingenic_adc_set_config(adc, JZ_ADC_REG_CFG_TOUCH_OPS_MASK, 0);
> +	writew(0, adc->base + JZ_ADC_REG_ADSAME);
> +	writew(0, adc->base + JZ_ADC_REG_ADWAIT);
> +	clk_disable(adc->clk);
> +
> +	return 0;
> +}
> +
> +static const struct iio_buffer_setup_ops ingenic_buffer_setup_ops = {
> +	.postenable = &ingenic_adc_buffer_enable,
> +	.predisable = &ingenic_adc_buffer_disable
> +};
> +
> +static irqreturn_t ingenic_adc_irq(int irq, void *data)
> +{
> +	struct iio_dev *iio_dev = data;
> +	struct ingenic_adc *adc = iio_priv(iio_dev);
> +	unsigned long mask = iio_dev->active_scan_mask[0];
> +	unsigned int i;
> +	u32 tdat[3];
> +
> +	for (i = 0; i < ARRAY_SIZE(tdat); mask >>= 2, i++) {
> +		if (mask & 0x3)
> +			tdat[i] = readl(adc->base + JZ_ADC_REG_ADTCH);
> +		else
> +			tdat[i] = 0;
> +	}
> +
> +	iio_push_to_buffers(iio_dev, tdat);
> +	writeb(JZ_ADC_IRQ_TOUCH, adc->base + JZ_ADC_REG_STATUS);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static int ingenic_adc_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	struct iio_dev *iio_dev;
>  	struct ingenic_adc *adc;
>  	const struct ingenic_adc_soc_data *soc_data;
> -	int ret;
> +	int irq, ret;
>  
>  	soc_data = device_get_match_data(dev);
>  	if (!soc_data)
> @@ -511,6 +745,17 @@ static int ingenic_adc_probe(struct platform_device *pdev)
>  	mutex_init(&adc->aux_lock);
>  	adc->soc_data = soc_data;
>  
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = devm_request_irq(dev, irq, ingenic_adc_irq, 0,
> +			       dev_name(dev), iio_dev);
> +	if (ret < 0) {
> +		dev_err(dev, "Failed to request irq: %d\n", ret);
> +		return ret;
> +	}
> +
>  	adc->base = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(adc->base))
>  		return PTR_ERR(adc->base);
> @@ -550,7 +795,8 @@ static int ingenic_adc_probe(struct platform_device *pdev)
>  
>  	iio_dev->dev.parent = dev;
>  	iio_dev->name = "jz-adc";
> -	iio_dev->modes = INDIO_DIRECT_MODE;
> +	iio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
> +	iio_dev->setup_ops = &ingenic_buffer_setup_ops;
>  	iio_dev->channels = soc_data->channels;
>  	iio_dev->num_channels = soc_data->num_channels;
>  	iio_dev->info = &ingenic_adc_info;