[media] cec: add STM32 cec driver

This patch add cec driver for STM32 platforms.
cec hardware block isn't not always used with hdmi so
cec notifier is not implemented. That will be done later
when STM32 DSI driver will be available.

Driver compliance has been tested with cec-ctl and cec-compliance
tools.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
[hans.verkuil@cisco.com: modified platform/Makefile to use obj-y]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

2 files changed, 363 insertions, 0 deletions

diff --git a/drivers/media/platform/stm32/Makefile b/drivers/media/platform/stm32/Makefile
index 9b606a70985d..07355091376b 100644
--- a/drivers/media/platform/stm32/Makefile
+++ b/drivers/media/platform/stm32/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_VIDEO_STM32_DCMI) += stm32-dcmi.o
+obj-$(CONFIG_VIDEO_STM32_HDMI_CEC) += stm32-cec.o
diff --git a/drivers/media/platform/stm32/stm32-cec.c b/drivers/media/platform/stm32/stm32-cec.c
new file mode 100644
index 000000000000..9ab896b01ee8
--- /dev/null
+++ b/drivers/media/platform/stm32/stm32-cec.c
@@ -0,0 +1,362 @@
+/*
+ * STM32 CEC driver
+ * Copyright (C) STMicroelectronics SA 2017
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#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)
+
+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;
+
+	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_LOG_ADDRS | CEC_CAP_PASSTHROUGH |
+		   CEC_CAP_TRANSMIT | CEC_CAP_RC | 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)) {
+		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)) {
+		ret = clk_prepare(cec->clk_hdmi_cec);
+		if (ret) {
+			dev_err(&pdev->dev, "Unable to prepare hdmi-cec clock\n");
+			return ret;
+		}
+	}
+
+	/*
+	 * 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)
+		return ret;
+
+	ret = cec_register_adapter(cec->adap, &pdev->dev);
+	if (ret) {
+		cec_delete_adapter(cec->adap);
+		return ret;
+	}
+
+	cec_hw_init(cec);
+
+	platform_set_drvdata(pdev, cec);
+
+	return 0;
+}
+
+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");