Message-ID: <20210715214001.GA25809@gofer.mess.org>
Date:   Thu, 15 Jul 2021 22:40:01 +0100
From:   Sean Young <sean@...s.org>
To:     Viktor Prutyanov <viktor.prutyanov@...stech.edu>
Cc:     mchehab@...nel.org, robh+dt@...nel.org, khilman@...libre.com,
        narmstrong@...libre.com, jbrunet@...libre.com,
        martin.blumenstingl@...glemail.com, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, rockosov@...il.com
Subject: Re: [PATCH v5 2/2] media: rc: introduce Meson IR TX driver

On Thu, Jul 15, 2021 at 12:27:06AM +0300, Viktor Prutyanov wrote:
> This patch adds the driver for Amlogic Meson IR transmitter.
> 
> Some Amlogic SoCs such as A311D and T950D4 have IR transmitter
> (also called blaster) controller onboard. It is capable of sending
> IR signals with arbitrary carrier frequency and duty cycle.
> 
> The driver supports 2 modulation clock sources:
>  - xtal3 clock (xtal divided by 3)
>  - 1us clock
> 
> Signed-off-by: Viktor Prutyanov <viktor.prutyanov@...stech.edu>
> ---
>  changes in v2:
>    - threaded IRQ removed, all stuff done in IRQ handler
>    - DIV_ROUND_CLOSEST_ULL replaced with DIV_ROUND_CLOSEST
>    - compatible changed to "amlogic,meson-g12a-irblaster"
>    - 'debug' parameter removed
>    - dprintk() replaced with dev_dbg()/dev_info()
>    - carrier frequency checked against 0
>    - device_name added
>  changes in v3:
>    - license header fixed
>    - 'max_fifo_level' parameter removed
>    - irq and clk_nr deleted from irblaster_dev struct
>    - some divisions replaced with DIV_ROUND_CLOSEST
>    - irb_send inlined
>    - fixed early completion in IRQ handler
>    - spin lock added before kfree
>  changes in v4:
>    - irblaster -> ir-tx renaming
>    - spin lock added before buffer allocation
>  changes in v5:
>    - spinlocks rework made in meson_irtx_transmit
>    - max_fifo_level replaced with fifo_threshold (max_fifo_level +
>      fifo_threshold == IRB_FIFO_LEN == 128)
>    - max-fifo-level -> amlogic,fifo-threshold
> 
>  drivers/media/rc/Kconfig       |  10 +
>  drivers/media/rc/Makefile      |   1 +
>  drivers/media/rc/meson-ir-tx.c | 410 +++++++++++++++++++++++++++++++++
>  3 files changed, 421 insertions(+)
>  create mode 100644 drivers/media/rc/meson-ir-tx.c
> 
> diff --git a/drivers/media/rc/Kconfig b/drivers/media/rc/Kconfig
> index d0a8326b75c2..fd5a7a058714 100644
> --- a/drivers/media/rc/Kconfig
> +++ b/drivers/media/rc/Kconfig
> @@ -246,6 +246,16 @@ config IR_MESON
>  	   To compile this driver as a module, choose M here: the
>  	   module will be called meson-ir.
>  
> +config IR_MESON_TX
> +	tristate "Amlogic Meson IR TX"
> +	depends on ARCH_MESON || COMPILE_TEST
> +	help
> +	   Say Y if you want to use the IR transmitter available on
> +	   Amlogic Meson SoCs.
> +
> +	   To compile this driver as a module, choose M here: the
> +	   module will be called meson-ir-tx.
> +
>  config IR_MTK
>  	tristate "Mediatek IR remote receiver"
>  	depends on ARCH_MEDIATEK || COMPILE_TEST
> diff --git a/drivers/media/rc/Makefile b/drivers/media/rc/Makefile
> index 692e9b6b203f..0db51fad27d6 100644
> --- a/drivers/media/rc/Makefile
> +++ b/drivers/media/rc/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_IR_ITE_CIR) += ite-cir.o
>  obj-$(CONFIG_IR_MCEUSB) += mceusb.o
>  obj-$(CONFIG_IR_FINTEK) += fintek-cir.o
>  obj-$(CONFIG_IR_MESON) += meson-ir.o
> +obj-$(CONFIG_IR_MESON_TX) += meson-ir-tx.o
>  obj-$(CONFIG_IR_NUVOTON) += nuvoton-cir.o
>  obj-$(CONFIG_IR_ENE) += ene_ir.o
>  obj-$(CONFIG_IR_REDRAT3) += redrat3.o
> diff --git a/drivers/media/rc/meson-ir-tx.c b/drivers/media/rc/meson-ir-tx.c
> new file mode 100644
> index 000000000000..1730af93e43d
> --- /dev/null
> +++ b/drivers/media/rc/meson-ir-tx.c
> @@ -0,0 +1,410 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/**
> + * meson-ir-tx.c - Amlogic Meson IR TX driver
> + *
> + * Copyright (c) 2021, SberDevices. All Rights Reserved.
> + *
> + * Author: Viktor Prutyanov <viktor.prutyanov@...stech.edu>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/sched.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/interrupt.h>
> +#include <linux/spinlock.h>
> +#include <linux/of_irq.h>
> +#include <linux/clk.h>
> +#include <linux/slab.h>
> +#include <media/rc-core.h>
> +
> +#define DEVICE_NAME	"Meson IR TX"
> +#define DRIVER_NAME	"meson-ir-tx"
> +
> +#define MIRTX_DEFAULT_CARRIER		38000
> +#define MIRTX_DEFAULT_DUTY_CYCLE	50
> +#define MIRTX_DEFAULT_FIFO_THD		32
> +
> +#define IRB_MOD_1US_CLK_RATE	1000000
> +
> +#define IRB_FIFO_LEN	128
> +
> +#define IRB_ADDR0	0x0
> +#define IRB_ADDR1	0x4
> +#define IRB_ADDR2	0x8
> +#define IRB_ADDR3	0xc
> +
> +#define IRB_MAX_DELAY	(1 << 10)
> +#define IRB_DELAY_MASK	(IRB_MAX_DELAY - 1)
> +
> +/* IRCTRL_IR_BLASTER_ADDR0 */
> +#define IRB_MOD_CLK(x)		((x) << 12)
> +#define IRB_MOD_SYS_CLK		0
> +#define IRB_MOD_XTAL3_CLK	1
> +#define IRB_MOD_1US_CLK		2
> +#define IRB_MOD_10US_CLK	3
> +#define IRB_INIT_HIGH		BIT(2)
> +#define IRB_ENABLE		BIT(0)
> +
> +/* IRCTRL_IR_BLASTER_ADDR2 */
> +#define IRB_MOD_COUNT(lo, hi)	((((lo) - 1) << 16) | ((hi) - 1))
> +
> +/* IRCTRL_IR_BLASTER_ADDR2 */
> +#define IRB_WRITE_FIFO	BIT(16)
> +#define IRB_MOD_ENABLE	BIT(12)
> +#define IRB_TB_1US	(0x0 << 10)
> +#define IRB_TB_10US	(0x1 << 10)
> +#define IRB_TB_100US	(0x2 << 10)
> +#define IRB_TB_MOD_CLK	(0x3 << 10)
> +
> +/* IRCTRL_IR_BLASTER_ADDR3 */
> +#define IRB_FIFO_THD_PENDING	BIT(16)
> +#define IRB_FIFO_IRQ_ENABLE	BIT(8)
> +
> +struct meson_irtx {
> +	struct device *dev;
> +	void __iomem *reg_base;
> +	u32 *buf;
> +	unsigned int buf_len;
> +	unsigned int buf_head;
> +	unsigned int carrier;
> +	unsigned int duty_cycle;
> +	spinlock_t lock;
> +	struct completion completion;
> +	unsigned int fifo_threshold;
> +	unsigned long clk_rate;
> +};
> +
> +static void meson_irtx_set_mod(struct meson_irtx *ir)
> +{
> +	unsigned int cnt = DIV_ROUND_CLOSEST(ir->clk_rate, ir->carrier);
> +	unsigned int pulse_cnt = DIV_ROUND_CLOSEST(cnt * ir->duty_cycle, 100);
> +	unsigned int space_cnt = cnt - pulse_cnt;
> +
> +	dev_dbg(ir->dev, "F_mod = %uHz, T_mod = %luns, duty_cycle = %u%%\n",
> +		ir->carrier, NSEC_PER_SEC / ir->clk_rate * cnt,
> +		100 * pulse_cnt / cnt);
> +
> +	writel(IRB_MOD_COUNT(pulse_cnt, space_cnt),
> +	       ir->reg_base + IRB_ADDR1);
> +}
> +
> +static void meson_irtx_setup(struct meson_irtx *ir, unsigned int clk_nr)
> +{
> +	/*
> +	 * Disable the TX, set modulator clock tick and set initialize
> +	 * output to be high. Set up carrier frequency and duty cycle. Then
> +	 * unset initialize output. Enable FIFO interrupt, set FIFO interrupt
> +	 * threshold. Finally, enable the transmitter back.
> +	 */
> +	writel(~IRB_ENABLE & (IRB_MOD_CLK(clk_nr) | IRB_INIT_HIGH),
> +	       ir->reg_base + IRB_ADDR0);
> +	meson_irtx_set_mod(ir);
> +	writel(readl(ir->reg_base + IRB_ADDR0) & ~IRB_INIT_HIGH,
> +	       ir->reg_base + IRB_ADDR0);
> +	writel(IRB_FIFO_IRQ_ENABLE | ir->fifo_threshold,
> +	       ir->reg_base + IRB_ADDR3);
> +	writel(readl(ir->reg_base + IRB_ADDR0) | IRB_ENABLE,
> +	       ir->reg_base + IRB_ADDR0);
> +}
> +
> +static u32 meson_irtx_prepare_pulse(struct meson_irtx *ir, unsigned int time)
> +{
> +	unsigned int delay;
> +	unsigned int tb = IRB_TB_MOD_CLK;
> +	unsigned int tb_us = DIV_ROUND_CLOSEST(USEC_PER_SEC, ir->carrier);
> +
> +	delay = (DIV_ROUND_CLOSEST(time, tb_us) - 1) & IRB_DELAY_MASK;
> +
> +	return ((IRB_WRITE_FIFO | IRB_MOD_ENABLE) | tb | delay);
> +}
> +
> +static u32 meson_irtx_prepare_space(struct meson_irtx *ir, unsigned int time)
> +{
> +	unsigned int delay;
> +	unsigned int tb = IRB_TB_100US;
> +	unsigned int tb_us = 100;
> +
> +	if (time <= IRB_MAX_DELAY) {
> +		tb = IRB_TB_1US;
> +		tb_us = 1;
> +	} else if (time <= 10 * IRB_MAX_DELAY) {
> +		tb = IRB_TB_10US;
> +		tb_us = 10;
> +	} else if (time <= 100 * IRB_MAX_DELAY) {
> +		tb = IRB_TB_100US;
> +		tb_us = 100;
> +	}
> +
> +	delay = (DIV_ROUND_CLOSEST(time, tb_us) - 1) & IRB_DELAY_MASK;
> +
> +	return ((IRB_WRITE_FIFO & ~IRB_MOD_ENABLE) | tb | delay);
> +}
> +
> +static void meson_irtx_send_buffer(struct meson_irtx *ir)
> +{
> +	unsigned int nr = 0;
> +	unsigned int max_fifo_level = IRB_FIFO_LEN - ir->fifo_threshold;
> +
> +	while (ir->buf_head < ir->buf_len && nr < max_fifo_level) {
> +		writel(ir->buf[ir->buf_head], ir->reg_base + IRB_ADDR2);
> +
> +		ir->buf_head++;
> +		nr++;
> +	}
> +}
> +
> +static bool meson_irtx_check_buf(struct meson_irtx *ir,
> +			  unsigned int *buf, unsigned int len)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < len; i++) {
> +		unsigned int max_tb_us;
> +		/*
> +		 * Max space timebase is 100 us.
> +		 * Pulse timebase equals to carrier period.
> +		 */
> +		if (i % 2 == 0)
> +			max_tb_us = USEC_PER_SEC / ir->carrier;
> +		else
> +			max_tb_us = 100;
> +
> +		if (buf[i] >= max_tb_us * IRB_MAX_DELAY)
> +			return false;
> +	}
> +
> +	return true;
> +}
> +
> +static void meson_irtx_fill_buf(struct meson_irtx *ir, u32 *dst_buf,
> +				unsigned int *src_buf, unsigned int len)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < len; i++) {
> +		if (i % 2 == 0)
> +			dst_buf[i] = meson_irtx_prepare_pulse(ir, src_buf[i]);
> +		else
> +			dst_buf[i] = meson_irtx_prepare_space(ir, src_buf[i]);
> +	}
> +}
> +
> +static irqreturn_t meson_irtx_irqhandler(int irq, void *data)
> +{
> +	unsigned long flags;
> +	struct meson_irtx *ir = data;
> +
> +	writel(readl(ir->reg_base + IRB_ADDR3) & ~IRB_FIFO_THD_PENDING,
> +	       ir->reg_base + IRB_ADDR3);
> +
> +	spin_lock_irqsave(&ir->lock, flags);
> +	if (ir->buf_head < ir->buf_len)
> +		meson_irtx_send_buffer(ir);
> +	else
> +		complete(&ir->completion);
> +	spin_unlock_irqrestore(&ir->lock, flags);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int meson_irtx_set_carrier(struct rc_dev *rc, u32 carrier)
> +{
> +	struct meson_irtx *ir = rc->priv;
> +
> +	if (carrier == 0)
> +		return -EINVAL;
> +
> +	ir->carrier = carrier;
> +	meson_irtx_set_mod(ir);
> +
> +	return 0;
> +}
> +
> +static int meson_irtx_set_duty_cycle(struct rc_dev *rc, u32 duty_cycle)
> +{
> +	struct meson_irtx *ir = rc->priv;
> +
> +	ir->duty_cycle = duty_cycle;
> +	meson_irtx_set_mod(ir);
> +
> +	return 0;
> +}
> +
> +static void meson_irtx_update_buf(struct meson_irtx *ir, u32 *buf,
> +				  unsigned int len, unsigned int head)
> +{
> +	ir->buf = buf;
> +	ir->buf_len = len;
> +	ir->buf_head = head;
> +}
> +
> +static int meson_irtx_transmit(struct rc_dev *rc, unsigned int *buf,
> +			       unsigned int len)
> +{
> +	unsigned long flags;
> +	struct meson_irtx *ir = rc->priv;
> +	u32 *tx_buf;
> +	int ret;
> +
> +	if (!meson_irtx_check_buf(ir, buf, len))
> +		return -EINVAL;
> +
> +	tx_buf = kmalloc_array(len, sizeof(u32), GFP_KERNEL);
> +	if (!tx_buf)
> +		return -ENOMEM;
> +
> +	meson_irtx_fill_buf(ir, tx_buf, buf, len);
> +	dev_dbg(ir->dev, "TX buffer filled, length = %u\n", len);
> +
> +	spin_lock_irqsave(&ir->lock, flags);
> +	meson_irtx_update_buf(ir, tx_buf, len, 0);
> +	reinit_completion(&ir->completion);
> +	meson_irtx_send_buffer(ir);
> +	spin_unlock_irqrestore(&ir->lock, flags);
> +
> +	ret = wait_for_completion_interruptible(&ir->completion);
> +	dev_dbg(ir->dev, "TX %s\n", ret ? "interrupted" : "completed");

Here two things can happen. One is, the process received a signal (e.g. ^C).
The other is that the hardware didn't issue any interrupts due some
problem somewhere. In the latter case, we only escape this
wait_for_completion_interruptable() when the user gets fed up and presses ^C
or something like that.

> +
> +	spin_lock_irqsave(&ir->lock, flags);
> +	kfree(ir->buf);
> +	meson_irtx_update_buf(ir, NULL, 0, 0);
> +	spin_unlock_irqrestore(&ir->lock, flags);

Now it is possible that the buffer gets cleared before that IR was sent,
if the signal was received early enough. This means not all the Tx was
completed.

> +
> +	return len;

Yet, we always return success.

In case no interrupts were generated we should return an error in a timely
manner, so the wait_for_completion() needs the timeout. You can use the
fact that the IR is never longer IR_MAX_DURATION (half a second currently).
Not sure what the returned error should be, maybe -ETIMEDOUT?

The problem with the interruptable wait is that a process can receive a
signal at any time, and now when this happens your IR gets truncated. I
don't think this is what you want.

Thanks

Sean

> +}
> +
> +static int meson_irtx_mod_clock_probe(struct meson_irtx *ir,
> +				      unsigned int *clk_nr)
> +{
> +	struct device_node *np = ir->dev->of_node;
> +	struct clk *clock;
> +
> +	if (!np)
> +		return -ENODEV;
> +
> +	clock = devm_clk_get(ir->dev, "xtal");
> +	if (IS_ERR(clock) || clk_prepare_enable(clock))
> +		return -ENODEV;
> +
> +	*clk_nr = IRB_MOD_XTAL3_CLK;
> +	ir->clk_rate = clk_get_rate(clock) / 3;
> +
> +	if (ir->clk_rate < IRB_MOD_1US_CLK_RATE) {
> +		*clk_nr = IRB_MOD_1US_CLK;
> +		ir->clk_rate = IRB_MOD_1US_CLK_RATE;
> +	}
> +
> +	dev_info(ir->dev, "F_clk = %luHz\n", ir->clk_rate);
> +
> +	return 0;
> +}
> +
> +static int __init meson_irtx_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct meson_irtx *ir;
> +	struct rc_dev *rc;
> +	int irq;
> +	unsigned int clk_nr;
> +	int ret;
> +
> +	ir = devm_kzalloc(dev, sizeof(*ir), GFP_KERNEL);
> +	if (!ir)
> +		return -ENOMEM;
> +
> +	ir->reg_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(ir->reg_base))
> +		return PTR_ERR(ir->reg_base);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		dev_err(dev, "no irq resource found\n");
> +		return -ENODEV;
> +	}
> +
> +	if (of_property_read_u32(dev->of_node, "amlogic,fifo-threshold",
> +				 &ir->fifo_threshold))
> +		ir->fifo_threshold = MIRTX_DEFAULT_FIFO_THD;
> +	else if (ir->fifo_threshold >= IRB_FIFO_LEN)
> +		ir->fifo_threshold = MIRTX_DEFAULT_FIFO_THD;
> +	dev_dbg(dev, "FIFO threshold set to %u\n", ir->fifo_threshold);
> +
> +	ir->dev = dev;
> +	ir->carrier = MIRTX_DEFAULT_CARRIER;
> +	ir->duty_cycle = MIRTX_DEFAULT_DUTY_CYCLE;
> +	init_completion(&ir->completion);
> +	spin_lock_init(&ir->lock);
> +
> +	ret = meson_irtx_mod_clock_probe(ir, &clk_nr);
> +	if (ret) {
> +		dev_err(dev, "modulator clock setup failed\n");
> +		return ret;
> +	}
> +	meson_irtx_setup(ir, clk_nr);
> +
> +	ret = devm_request_irq(dev, irq,
> +			       meson_irtx_irqhandler,
> +			       IRQF_TRIGGER_RISING,
> +			       DRIVER_NAME, ir);
> +	if (ret) {
> +		dev_err(dev, "irq request failed\n");
> +		return ret;
> +	}
> +
> +	rc = rc_allocate_device(RC_DRIVER_IR_RAW_TX);
> +	if (!rc)
> +		return -ENOMEM;
> +
> +	rc->driver_name = DRIVER_NAME;
> +	rc->device_name = DEVICE_NAME;
> +	rc->priv = ir;
> +
> +	rc->tx_ir = meson_irtx_transmit;
> +	rc->s_tx_carrier = meson_irtx_set_carrier;
> +	rc->s_tx_duty_cycle = meson_irtx_set_duty_cycle;
> +
> +	ret = rc_register_device(rc);
> +	if (ret < 0) {
> +		dev_err(dev, "rc_dev registration failed\n");
> +		rc_free_device(rc);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, rc);
> +
> +	return 0;
> +}
> +
> +static int meson_irtx_remove(struct platform_device *pdev)
> +{
> +	struct rc_dev *rc = platform_get_drvdata(pdev);
> +
> +	rc_unregister_device(rc);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id meson_irtx_dt_match[] = {
> +	{
> +		.compatible = "amlogic,meson-g12a-ir-tx",
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, meson_irtx_dt_match);
> +
> +static struct platform_driver meson_irtx_pd = {
> +	.remove = meson_irtx_remove,
> +	.driver = {
> +		.name = DRIVER_NAME,
> +		.owner  = THIS_MODULE,
> +		.of_match_table = meson_irtx_dt_match,
> +	},
> +};
> +
> +module_platform_driver_probe(meson_irtx_pd, meson_irtx_probe);
> +
> +MODULE_DESCRIPTION("Meson IR TX driver");
> +MODULE_AUTHOR("Viktor Prutyanov <viktor.prutyanov@...stech.edu>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.21.0

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