stm32-cec.c

// SPDX-License-Identifier: GPL-2.0
/*
 * STM32 CEC driver
 * Copyright (C) STMicroelectronics SA 2017
 *
 */

#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>

#include <media/cec.h>

#define CEC_NAME	"stm32-cec"

/* CEC registers  */
#define CEC_CR		0x0000 /* Control Register */
#define CEC_CFGR	0x0004 /* ConFiGuration Register */
#define CEC_TXDR	0x0008 /* Rx data Register */
#define CEC_RXDR	0x000C /* Rx data Register */
#define CEC_ISR		0x0010 /* Interrupt and status Register */
#define CEC_IER		0x0014 /* Interrupt enable Register */

#define TXEOM		BIT(2)
#define TXSOM		BIT(1)
#define CECEN		BIT(0)

#define LSTN		BIT(31)
#define OAR		GENMASK(30, 16)
#define SFTOP		BIT(8)
#define BRDNOGEN	BIT(7)
#define LBPEGEN		BIT(6)
#define BREGEN		BIT(5)
#define BRESTP		BIT(4)
#define RXTOL		BIT(3)
#define SFT		GENMASK(2, 0)
#define FULL_CFG	(LSTN | SFTOP | BRDNOGEN | LBPEGEN | BREGEN | BRESTP \
			 | RXTOL)

#define TXACKE		BIT(12)
#define TXERR		BIT(11)
#define TXUDR		BIT(10)
#define TXEND		BIT(9)
#define TXBR		BIT(8)
#define ARBLST		BIT(7)
#define RXACKE		BIT(6)
#define RXOVR		BIT(2)
#define RXEND		BIT(1)
#define RXBR		BIT(0)

#define ALL_TX_IT	(TXEND | TXBR | TXACKE | TXERR | TXUDR | ARBLST)
#define ALL_RX_IT	(RXEND | RXBR | RXACKE | RXOVR)

/*
 * 400 ms is the time it takes for one 16 byte message to be
 * transferred and 5 is the maximum number of retries. Add
 * another 100 ms as a margin.
 */
#define CEC_XFER_TIMEOUT_MS (5 * 400 + 100)

struct stm32_cec {
	struct cec_adapter	*adap;
	struct device		*dev;
	struct clk		*clk_cec;
	struct clk		*clk_hdmi_cec;
	struct reset_control	*rstc;
	struct regmap		*regmap;
	int			irq;
	u32			irq_status;
	struct cec_msg		rx_msg;
	struct cec_msg		tx_msg;
	int			tx_cnt;
};

static void cec_hw_init(struct stm32_cec *cec)
{
	regmap_update_bits(cec->regmap, CEC_CR, TXEOM | TXSOM | CECEN, 0);

	regmap_update_bits(cec->regmap, CEC_IER, ALL_TX_IT | ALL_RX_IT,
			   ALL_TX_IT | ALL_RX_IT);

	regmap_update_bits(cec->regmap, CEC_CFGR, FULL_CFG, FULL_CFG);
}

static void stm32_tx_done(struct stm32_cec *cec, u32 status)
{
	if (status & (TXERR | TXUDR)) {
		cec_transmit_done(cec->adap, CEC_TX_STATUS_ERROR,
				  0, 0, 0, 1);
		return;
	}

	if (status & ARBLST) {
		cec_transmit_done(cec->adap, CEC_TX_STATUS_ARB_LOST,
				  1, 0, 0, 0);
		return;
	}

	if (status & TXACKE) {
		cec_transmit_done(cec->adap, CEC_TX_STATUS_NACK,
				  0, 1, 0, 0);
		return;
	}

	if (cec->irq_status & TXBR) {
		/* send next byte */
		if (cec->tx_cnt < cec->tx_msg.len)
			regmap_write(cec->regmap, CEC_TXDR,
				     cec->tx_msg.msg[cec->tx_cnt++]);

		/* TXEOM is set to command transmission of the last byte */
		if (cec->tx_cnt == cec->tx_msg.len)
			regmap_update_bits(cec->regmap, CEC_CR, TXEOM, TXEOM);
	}

	if (cec->irq_status & TXEND)
		cec_transmit_done(cec->adap, CEC_TX_STATUS_OK, 0, 0, 0, 0);
}

static void stm32_rx_done(struct stm32_cec *cec, u32 status)
{
	if (cec->irq_status & (RXACKE | RXOVR)) {
		cec->rx_msg.len = 0;
		return;
	}

	if (cec->irq_status & RXBR) {
		u32 val;

		regmap_read(cec->regmap, CEC_RXDR, &val);
		cec->rx_msg.msg[cec->rx_msg.len++] = val & 0xFF;
	}

	if (cec->irq_status & RXEND) {
		cec_received_msg(cec->adap, &cec->rx_msg);
		cec->rx_msg.len = 0;
	}
}

static irqreturn_t stm32_cec_irq_thread(int irq, void *arg)
{
	struct stm32_cec *cec = arg;

	if (cec->irq_status & ALL_TX_IT)
		stm32_tx_done(cec, cec->irq_status);

	if (cec->irq_status & ALL_RX_IT)
		stm32_rx_done(cec, cec->irq_status);

	cec->irq_status = 0;

	return IRQ_HANDLED;
}

static irqreturn_t stm32_cec_irq_handler(int irq, void *arg)
{
	struct stm32_cec *cec = arg;

	regmap_read(cec->regmap, CEC_ISR, &cec->irq_status);

	regmap_update_bits(cec->regmap, CEC_ISR,
			   ALL_TX_IT | ALL_RX_IT,
			   ALL_TX_IT | ALL_RX_IT);

	return IRQ_WAKE_THREAD;
}

static int stm32_cec_adap_enable(struct cec_adapter *adap, bool enable)
{
	struct stm32_cec *cec = adap->priv;
	int ret = 0;

	if (enable) {
		ret = clk_enable(cec->clk_cec);
		if (ret)
			dev_err(cec->dev, "fail to enable cec clock\n");

		clk_enable(cec->clk_hdmi_cec);
		regmap_update_bits(cec->regmap, CEC_CR, CECEN, CECEN);
	} else {
		clk_disable(cec->clk_cec);
		clk_disable(cec->clk_hdmi_cec);
		regmap_update_bits(cec->regmap, CEC_CR, CECEN, 0);
	}

	return ret;
}

static int stm32_cec_adap_log_addr(struct cec_adapter *adap, u8 logical_addr)
{
	struct stm32_cec *cec = adap->priv;
	u32 oar = (1 << logical_addr) << 16;
	u32 val;

	/* Poll every 100µs the register CEC_CR to wait end of transmission */
	regmap_read_poll_timeout(cec->regmap, CEC_CR, val, !(val & TXSOM),
				 100, CEC_XFER_TIMEOUT_MS * 1000);
	regmap_update_bits(cec->regmap, CEC_CR, CECEN, 0);

	if (logical_addr == CEC_LOG_ADDR_INVALID)
		regmap_update_bits(cec->regmap, CEC_CFGR, OAR, 0);
	else
		regmap_update_bits(cec->regmap, CEC_CFGR, oar, oar);

	regmap_update_bits(cec->regmap, CEC_CR, CECEN, CECEN);

	return 0;
}

static int stm32_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,
				   u32 signal_free_time, struct cec_msg *msg)
{
	struct stm32_cec *cec = adap->priv;

	/* Copy message */
	cec->tx_msg = *msg;
	cec->tx_cnt = 0;

	/*
	 * If the CEC message consists of only one byte,
	 * TXEOM must be set before of TXSOM.
	 */
	if (cec->tx_msg.len == 1)
		regmap_update_bits(cec->regmap, CEC_CR, TXEOM, TXEOM);

	/* TXSOM is set to command transmission of the first byte */
	regmap_update_bits(cec->regmap, CEC_CR, TXSOM, TXSOM);

	/* Write the header (first byte of message) */
	regmap_write(cec->regmap, CEC_TXDR, cec->tx_msg.msg[0]);
	cec->tx_cnt++;

	return 0;
}

static const struct cec_adap_ops stm32_cec_adap_ops = {
	.adap_enable = stm32_cec_adap_enable,
	.adap_log_addr = stm32_cec_adap_log_addr,
	.adap_transmit = stm32_cec_adap_transmit,
};

static const struct regmap_config stm32_cec_regmap_cfg = {
	.reg_bits = 32,
	.val_bits = 32,
	.reg_stride = sizeof(u32),
	.max_register = 0x14,
	.fast_io = true,
};

static int stm32_cec_probe(struct platform_device *pdev)
{
	u32 caps = CEC_CAP_DEFAULTS | CEC_CAP_PHYS_ADDR | CEC_MODE_MONITOR_ALL;
	struct resource *res;
	struct stm32_cec *cec;
	void __iomem *mmio;
	int ret;

	cec = devm_kzalloc(&pdev->dev, sizeof(*cec), GFP_KERNEL);
	if (!cec)
		return -ENOMEM;

	cec->dev = &pdev->dev;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	mmio = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(mmio))
		return PTR_ERR(mmio);

	cec->regmap = devm_regmap_init_mmio_clk(&pdev->dev, "cec", mmio,
						&stm32_cec_regmap_cfg);

	if (IS_ERR(cec->regmap))
		return PTR_ERR(cec->regmap);

	cec->irq = platform_get_irq(pdev, 0);
	if (cec->irq < 0)
		return cec->irq;

	ret = devm_request_threaded_irq(&pdev->dev, cec->irq,
					stm32_cec_irq_handler,
					stm32_cec_irq_thread,
					0,
					pdev->name, cec);
	if (ret)
		return ret;

	cec->clk_cec = devm_clk_get(&pdev->dev, "cec");
	if (IS_ERR(cec->clk_cec)) {
		if (PTR_ERR(cec->clk_cec) != -EPROBE_DEFER)
			dev_err(&pdev->dev, "Cannot get cec clock\n");

		return PTR_ERR(cec->clk_cec);
	}

	ret = clk_prepare(cec->clk_cec);
	if (ret) {
		dev_err(&pdev->dev, "Unable to prepare cec clock\n");
		return ret;
	}

	cec->clk_hdmi_cec = devm_clk_get(&pdev->dev, "hdmi-cec");
	if (IS_ERR(cec->clk_hdmi_cec) &&
	    PTR_ERR(cec->clk_hdmi_cec) == -EPROBE_DEFER) {
		ret = -EPROBE_DEFER;
		goto err_unprepare_cec_clk;
	}

	if (!IS_ERR(cec->clk_hdmi_cec)) {
		ret = clk_prepare(cec->clk_hdmi_cec);
		if (ret) {
			dev_err(&pdev->dev, "Can't prepare hdmi-cec clock\n");
			goto err_unprepare_cec_clk;
		}
	}

	/*
	 * CEC_CAP_PHYS_ADDR caps should be removed when a cec notifier is
	 * available for example when a drm driver can provide edid
	 */
	cec->adap = cec_allocate_adapter(&stm32_cec_adap_ops, cec,
			CEC_NAME, caps,	CEC_MAX_LOG_ADDRS);
	ret = PTR_ERR_OR_ZERO(cec->adap);
	if (ret)
		goto err_unprepare_hdmi_cec_clk;

	ret = cec_register_adapter(cec->adap, &pdev->dev);
	if (ret)
		goto err_delete_adapter;

	cec_hw_init(cec);

	platform_set_drvdata(pdev, cec);

	return 0;

err_delete_adapter:
	cec_delete_adapter(cec->adap);

err_unprepare_hdmi_cec_clk:
	clk_unprepare(cec->clk_hdmi_cec);

err_unprepare_cec_clk:
	clk_unprepare(cec->clk_cec);
	return ret;
}

static int stm32_cec_remove(struct platform_device *pdev)
{
	struct stm32_cec *cec = platform_get_drvdata(pdev);

	clk_unprepare(cec->clk_cec);
	clk_unprepare(cec->clk_hdmi_cec);

	cec_unregister_adapter(cec->adap);

	return 0;
}

static const struct of_device_id stm32_cec_of_match[] = {
	{ .compatible = "st,stm32-cec" },
	{ /* end node */ }
};
MODULE_DEVICE_TABLE(of, stm32_cec_of_match);

static struct platform_driver stm32_cec_driver = {
	.probe  = stm32_cec_probe,
	.remove = stm32_cec_remove,
	.driver = {
		.name		= CEC_NAME,
		.of_match_table = stm32_cec_of_match,
	},
};

module_platform_driver(stm32_cec_driver);

MODULE_AUTHOR("Benjamin Gaignard <benjamin.gaignard@st.com>");
MODULE_AUTHOR("Yannick Fertre <yannick.fertre@st.com>");
MODULE_DESCRIPTION("STMicroelectronics STM32 Consumer Electronics Control");
MODULE_LICENSE("GPL v2");