Re: [PATCH 4/4] [media] rc: pwm-ir-tx: add new driver

[Sean Young <sean-hENCXIMQXOg@public.gmane.org>]

On Sun, Jul 02, 2017 at 12:06:13PM +0100, Sean Young wrote:
> This is new driver which uses pwm, so it is more power-efficient
> than the bit banging gpio-ir-tx driver.
> 
> Signed-off-by: Sean Young <sean-hENCXIMQXOg@public.gmane.org>
> ---
>  .../devicetree/bindings/leds/irled/pwm-ir-tx.txt   |  13 ++
>  drivers/media/rc/Kconfig                           |  12 ++
>  drivers/media/rc/Makefile                          |   1 +
>  drivers/media/rc/pwm-ir-tx.c                       | 165 +++++++++++++++++++++
>  4 files changed, 191 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/irled/pwm-ir-tx.txt
>  create mode 100644 drivers/media/rc/pwm-ir-tx.c
> 
> diff --git a/Documentation/devicetree/bindings/leds/irled/pwm-ir-tx.txt b/Documentation/devicetree/bindings/leds/irled/pwm-ir-tx.txt
> new file mode 100644
> index 0000000..6887a71
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/irled/pwm-ir-tx.txt
> @@ -0,0 +1,13 @@
> +Device tree bindings for IR LED connected through pwm pin which is used as
> +IR transmitter.
> +
> +Required properties:
> +- compatible: should be "pwm-ir-tx".
> +- pwms : PWM property to point to the PWM device (phandle)/port (id) and to
> +  specify the period time to be used: <&phandle id period_ns>;
> +
> +Example:
> +	irled {
> +		compatible = "pwm-ir-tx";
> +		pwms = <&pwm0 0 10000000>;
> +	};
> diff --git a/drivers/media/rc/Kconfig b/drivers/media/rc/Kconfig
> index ad54011..c5338e3 100644
> --- a/drivers/media/rc/Kconfig
> +++ b/drivers/media/rc/Kconfig
> @@ -399,6 +399,18 @@ config IR_GPIO_TX
>  	   To compile this driver as a module, choose M here: the module will
>  	   be called gpio-ir-tx.
>  
> +config IR_PWM_TX
> +	tristate "PWM IR transmitter"
> +	depends on RC_CORE
> +	depends on LIRC
> +	depends on PWM
> +	---help---
> +	   Say Y if you want to use a PWM based IR transmitter. This is
> +	   more power efficient than the bit banging gpio driver.
> +
> +	   To compile this driver as a module, choose M here: the module will
> +	   be called pwm-ir-tx.
> +
>  config RC_ST
>  	tristate "ST remote control receiver"
>  	depends on RC_CORE
> diff --git a/drivers/media/rc/Makefile b/drivers/media/rc/Makefile
> index 3e64a4e..466c402 100644
> --- a/drivers/media/rc/Makefile
> +++ b/drivers/media/rc/Makefile
> @@ -33,6 +33,7 @@ obj-$(CONFIG_IR_WINBOND_CIR) += winbond-cir.o
>  obj-$(CONFIG_RC_LOOPBACK) += rc-loopback.o
>  obj-$(CONFIG_IR_GPIO_CIR) += gpio-ir-recv.o
>  obj-$(CONFIG_IR_GPIO_TX) += gpio-ir-tx.o
> +obj-$(CONFIG_IR_PWM_TX) += pwm-ir-tx.o
>  obj-$(CONFIG_IR_IGORPLUGUSB) += igorplugusb.o
>  obj-$(CONFIG_IR_IGUANA) += iguanair.o
>  obj-$(CONFIG_IR_TTUSBIR) += ttusbir.o
> diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c
> new file mode 100644
> index 0000000..1ab10b4
> --- /dev/null
> +++ b/drivers/media/rc/pwm-ir-tx.c
> @@ -0,0 +1,165 @@
> +/*
> + * Copyright (C) 2017 Sean Young <sean-hENCXIMQXOg@public.gmane.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/pwm.h>
> +#include <linux/delay.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <media/rc-core.h>
> +
> +#define DRIVER_NAME	"pwm-ir-tx"
> +#define DEVICE_NAME	"PWM IR Transmitter"
> +
> +struct pwm_ir {
> +	struct pwm_device *pwm;
> +	unsigned int carrier;
> +	unsigned int duty_cycle;
> +	/* One transmission at a time */
> +	struct mutex lock;
> +};
> +
> +static const struct of_device_id pwm_ir_of_match[] = {
> +	{ .compatible = "pwm-ir-tx", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, pwm_ir_of_match);
> +
> +static int pwm_ir_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
> +{
> +	struct pwm_ir *pwm_ir = dev->priv;
> +
> +	pwm_ir->duty_cycle = duty_cycle;
> +
> +	return 0;
> +}
> +
> +static int pwm_ir_set_carrier(struct rc_dev *dev, u32 carrier)
> +{
> +	struct pwm_ir *pwm_ir = dev->priv;
> +
> +	if (!carrier)
> +		return -EINVAL;
> +
> +	pwm_ir->carrier = carrier;
> +
> +	return 0;
> +}
> +
> +static int pwm_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
> +		     unsigned int count)
> +{
> +	struct pwm_ir *pwm_ir = dev->priv;
> +	struct pwm_device *pwm = pwm_ir->pwm;
> +	int i, duty, period;
> +	ktime_t edge;
> +	s64 delta;
> +
> +	if (mutex_lock_interruptible(&pwm_ir->lock))
> +		return -ERESTARTSYS;
> +
> +	period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, pwm_ir->carrier);
> +	duty = DIV_ROUND_CLOSEST(pwm_ir->duty_cycle * period, 100);
> +
> +	pwm_config(pwm, duty, period);
> +
> +	edge = ktime_get();
> +
> +	for (i = 0; i < count; i++) {
> +		if (i % 2) // space
> +			pwm_disable(pwm);
> +		else
> +			pwm_enable(pwm);
> +
> +		edge = ktime_add_us(edge, txbuf[i]);
> +		delta = ktime_us_delta(edge, ktime_get());
> +		if (delta > 0)
> +			usleep_range(delta, delta + 10);
> +	}
> +
> +	pwm_disable(pwm);
> +
> +	mutex_unlock(&pwm_ir->lock);
> +
> +	return count;
> +}
> +
> +static int pwm_ir_probe(struct platform_device *pdev)
> +{
> +	struct pwm_ir *pwm_ir;
> +	struct rc_dev *rcdev;
> +	int rc;
> +
> +	pwm_ir = devm_kzalloc(&pdev->dev, sizeof(*pwm_ir), GFP_KERNEL);
> +	if (!pwm_ir)
> +		return -ENOMEM;
> +
> +	pwm_ir->pwm = devm_pwm_get(&pdev->dev, NULL);
> +	if (IS_ERR(pwm_ir->pwm))
> +		return PTR_ERR(pwm_ir->pwm);
> +
> +	pwm_ir->carrier = 38000;
> +	pwm_ir->duty_cycle = 50;
> +	mutex_init(&pwm_ir->lock);
> +
> +	rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
> +	if (!rcdev)
> +		return -ENOMEM;
> +
> +	rcdev->priv = pwm_ir;
> +	rcdev->driver_name = DRIVER_NAME;
> +	rcdev->device_name = DEVICE_NAME;
> +	rcdev->tx_ir = pwm_ir_tx;
> +	rcdev->s_tx_duty_cycle = pwm_ir_set_duty_cycle;
> +	rcdev->s_tx_carrier = pwm_ir_set_carrier;
> +
> +	rc = devm_rc_register_device(&pdev->dev, rcdev);
> +	if (rc < 0) {
> +		dev_err(&pdev->dev, "failed to register rc device\n");
> +		return rc;
> +	}
> +
> +	platform_set_drvdata(pdev, pwm_ir);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static int pwm_ir_suspend(struct platform_device *dev, pm_message_t state)
> +{
> +	struct pwm_ir *pwm_ir = platform_get_drvdata(dev);
> +
> +	if (mutex_is_locked(&pwm_ir->lock))
> +		return -EAGAIN;
> +
> +	return 0;
> +}

So this suspend function exists so that suspend does not happen while we're
transmitting; but all processing are frozen before the suspend gets called,
so we're too late in that case.

Besiders, during transmission in pwm_ir_tx() we're never in interruptable
sleep so this problem should not exist anyway.

Sean

> +#else
> +#define pwm_ir_suspend NULL
> +#endif
> +
> +static struct platform_driver pwm_ir_driver = {
> +	.probe = pwm_ir_probe,
> +	.suspend = pwm_ir_suspend,
> +	.driver = {
> +		.name	= DRIVER_NAME,
> +		.of_match_table = of_match_ptr(pwm_ir_of_match),
> +	},
> +};
> +module_platform_driver(pwm_ir_driver);
> +
> +MODULE_DESCRIPTION("PWM IR Transmitter");
> +MODULE_AUTHOR("Sean Young <sean-hENCXIMQXOg@public.gmane.org>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.9.4
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