phy: cadence: Add Cadence D-PHY Rx driver

The Cadence D-PHY can be configured in Tx (DSI) mode or Rx (CSI) mode.
Both modes have a different programming sequence and share little among
them. In addition, a PHY configured in Tx mode cannot be used in Rx mode
and vice versa. For this reason, create a separate driver for the Rx
mode to make it easier to read and maintain.

Signed-off-by: Pratyush Yadav <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/phy/cadence/Kconfig

···
 	  system. If M is selected, the module will be called
 	  cdns-dphy.
 
+config PHY_CADENCE_DPHY_RX
+	tristate "Cadence D-PHY Rx Support"
+	depends on HAS_IOMEM && OF
+	select GENERIC_PHY
+	select GENERIC_PHY_MIPI_DPHY
+	help
+	  Support for Cadence D-PHY in Rx configuration.
+
 config PHY_CADENCE_SIERRA
 	tristate "Cadence Sierra PHY Driver"
 	depends on OF && HAS_IOMEM && RESET_CONTROLLER

drivers/phy/cadence/Makefile

···
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_PHY_CADENCE_TORRENT)	+= phy-cadence-torrent.o
 obj-$(CONFIG_PHY_CADENCE_DPHY)	+= cdns-dphy.o
+obj-$(CONFIG_PHY_CADENCE_DPHY_RX)	+= cdns-dphy-rx.o
 obj-$(CONFIG_PHY_CADENCE_SIERRA)	+= phy-cadence-sierra.o
 obj-$(CONFIG_PHY_CADENCE_SALVO)	+= phy-cadence-salvo.o

drivers/phy/cadence/cdns-dphy-rx.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Texas Instruments Incorporated - https://www.ti.com/
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/phy/phy.h>
+#include <linux/phy/phy-mipi-dphy.h>
+#include <linux/platform_device.h>
+
+#define DPHY_PMA_CMN(reg)		(reg)
+#define DPHY_PCS(reg)			(0xb00 + (reg))
+#define DPHY_ISO(reg)			(0xc00 + (reg))
+
+#define DPHY_CMN_SSM			DPHY_PMA_CMN(0x20)
+#define DPHY_CMN_RX_MODE_EN		BIT(10)
+#define DPHY_CMN_RX_BANDGAP_TIMER_MASK	GENMASK(8, 1)
+#define DPHY_CMN_SSM_EN			BIT(0)
+
+#define DPHY_CMN_RX_BANDGAP_TIMER	0x14
+
+#define DPHY_BAND_CFG			DPHY_PCS(0x0)
+#define DPHY_BAND_CFG_RIGHT_BAND	GENMASK(9, 5)
+#define DPHY_BAND_CFG_LEFT_BAND		GENMASK(4, 0)
+
+#define DPHY_POWER_ISLAND_EN_DATA	DPHY_PCS(0x8)
+#define DPHY_POWER_ISLAND_EN_DATA_VAL	0xaaaaaaaa
+
+#define DPHY_POWER_ISLAND_EN_CLK	DPHY_PCS(0xc)
+#define DPHY_POWER_ISLAND_EN_CLK_VAL	0xaa
+
+#define DPHY_ISO_CL_CTRL_L		DPHY_ISO(0x10)
+#define DPHY_ISO_DL_CTRL_L0		DPHY_ISO(0x14)
+#define DPHY_ISO_DL_CTRL_L1		DPHY_ISO(0x20)
+#define DPHY_ISO_DL_CTRL_L2		DPHY_ISO(0x30)
+#define DPHY_ISO_DL_CTRL_L3		DPHY_ISO(0x3c)
+
+#define DPHY_ISO_LANE_READY_BIT		0
+#define DPHY_ISO_LANE_READY_TIMEOUT_MS	100UL
+
+#define DPHY_LANES_MIN			1
+#define DPHY_LANES_MAX			4
+
+struct cdns_dphy_rx {
+	void __iomem *regs;
+	struct device *dev;
+	struct phy *phy;
+};
+
+struct cdns_dphy_rx_band {
+	/* Rates are in Mbps. */
+	unsigned int min_rate;
+	unsigned int max_rate;
+};
+
+/* Order of bands is important since the index is the band number. */
+static const struct cdns_dphy_rx_band bands[] = {
+	{ 80, 100 }, { 100, 120 }, { 120, 160 }, { 160, 200 }, { 200, 240 },
+	{ 240, 280 }, { 280, 320 }, { 320, 360 }, { 360, 400 }, { 400, 480 },
+	{ 480, 560 }, { 560, 640 }, { 640, 720 }, { 720, 800 }, { 800, 880 },
+	{ 880, 1040 }, { 1040, 1200 }, { 1200, 1350 }, { 1350, 1500 },
+	{ 1500, 1750 }, { 1750, 2000 }, { 2000, 2250 }, { 2250, 2500 }
+};
+
+static int cdns_dphy_rx_power_on(struct phy *phy)
+{
+	struct cdns_dphy_rx *dphy = phy_get_drvdata(phy);
+
+	/* Start RX state machine. */
+	writel(DPHY_CMN_SSM_EN | DPHY_CMN_RX_MODE_EN |
+	       FIELD_PREP(DPHY_CMN_RX_BANDGAP_TIMER_MASK,
+			  DPHY_CMN_RX_BANDGAP_TIMER),
+	       dphy->regs + DPHY_CMN_SSM);
+
+	return 0;
+}
+
+static int cdns_dphy_rx_power_off(struct phy *phy)
+{
+	struct cdns_dphy_rx *dphy = phy_get_drvdata(phy);
+
+	writel(0, dphy->regs + DPHY_CMN_SSM);
+
+	return 0;
+}
+
+static int cdns_dphy_rx_get_band_ctrl(unsigned long hs_clk_rate)
+{
+	unsigned int rate, i;
+
+	rate = hs_clk_rate / 1000000UL;
+	/* Since CSI-2 clock is DDR, the bit rate is twice the clock rate. */
+	rate *= 2;
+
+	if (rate < bands[0].min_rate)
+		return -EOPNOTSUPP;
+
+	for (i = 0; i < ARRAY_SIZE(bands); i++)
+		if (rate < bands[i].max_rate)
+			return i;
+
+	return -EOPNOTSUPP;
+}
+
+static inline int cdns_dphy_rx_wait_for_bit(void __iomem *addr,
+					    unsigned int bit)
+{
+	u32 val;
+
+	return readl_relaxed_poll_timeout(addr, val, val & BIT(bit), 10,
+					  DPHY_ISO_LANE_READY_TIMEOUT_MS * 1000);
+}
+
+static int cdns_dphy_rx_wait_lane_ready(struct cdns_dphy_rx *dphy,
+					unsigned int lanes)
+{
+	static const u32 data_lane_ctrl[] = {DPHY_ISO_DL_CTRL_L0,
+					     DPHY_ISO_DL_CTRL_L1,
+					     DPHY_ISO_DL_CTRL_L2,
+					     DPHY_ISO_DL_CTRL_L3};
+	void __iomem *reg = dphy->regs;
+	unsigned int i;
+	int ret;
+
+	/* Clock lane */
+	ret = cdns_dphy_rx_wait_for_bit(reg + DPHY_ISO_CL_CTRL_L,
+					DPHY_ISO_LANE_READY_BIT);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < lanes; i++) {
+		ret = cdns_dphy_rx_wait_for_bit(reg + data_lane_ctrl[i],
+						DPHY_ISO_LANE_READY_BIT);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int cdns_dphy_rx_configure(struct phy *phy,
+				  union phy_configure_opts *opts)
+{
+	struct cdns_dphy_rx *dphy = phy_get_drvdata(phy);
+	unsigned int reg, lanes = opts->mipi_dphy.lanes;
+	int band_ctrl, ret;
+
+	/* Data lanes. Minimum one lane is mandatory. */
+	if (lanes < DPHY_LANES_MIN || lanes > DPHY_LANES_MAX)
+		return -EINVAL;
+
+	band_ctrl = cdns_dphy_rx_get_band_ctrl(opts->mipi_dphy.hs_clk_rate);
+	if (band_ctrl < 0)
+		return band_ctrl;
+
+	reg = FIELD_PREP(DPHY_BAND_CFG_LEFT_BAND, band_ctrl) |
+	      FIELD_PREP(DPHY_BAND_CFG_RIGHT_BAND, band_ctrl);
+	writel(reg, dphy->regs + DPHY_BAND_CFG);
+
+	/*
+	 * Set the required power island phase 2 time. This is mandated by DPHY
+	 * specs.
+	 */
+	reg = DPHY_POWER_ISLAND_EN_DATA_VAL;
+	writel(reg, dphy->regs + DPHY_POWER_ISLAND_EN_DATA);
+	reg = DPHY_POWER_ISLAND_EN_CLK_VAL;
+	writel(reg, dphy->regs + DPHY_POWER_ISLAND_EN_CLK);
+
+	ret = cdns_dphy_rx_wait_lane_ready(dphy, lanes);
+	if (ret) {
+		dev_err(dphy->dev, "DPHY wait for lane ready timeout\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int cdns_dphy_rx_validate(struct phy *phy, enum phy_mode mode,
+				 int submode, union phy_configure_opts *opts)
+{
+	int ret;
+
+	if (mode != PHY_MODE_MIPI_DPHY)
+		return -EINVAL;
+
+	ret = cdns_dphy_rx_get_band_ctrl(opts->mipi_dphy.hs_clk_rate);
+	if (ret < 0)
+		return ret;
+
+	return phy_mipi_dphy_config_validate(&opts->mipi_dphy);
+}
+
+static const struct phy_ops cdns_dphy_rx_ops = {
+	.power_on = cdns_dphy_rx_power_on,
+	.power_off = cdns_dphy_rx_power_off,
+	.configure = cdns_dphy_rx_configure,
+	.validate = cdns_dphy_rx_validate,
+};
+
+static int cdns_dphy_rx_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct phy_provider *provider;
+	struct cdns_dphy_rx *dphy;
+
+	dphy = devm_kzalloc(dev, sizeof(*dphy), GFP_KERNEL);
+	if (!dphy)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, dphy);
+	dphy->dev = dev;
+
+	dphy->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(dphy->regs))
+		return PTR_ERR(dphy->regs);
+
+	dphy->phy = devm_phy_create(dev, NULL, &cdns_dphy_rx_ops);
+	if (IS_ERR(dphy->phy)) {
+		dev_err(dev, "Failed to create PHY: %ld\n", PTR_ERR(dphy->phy));
+		return PTR_ERR(dphy->phy);
+	}
+
+	phy_set_drvdata(dphy->phy, dphy);
+	provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
+	if (IS_ERR(provider)) {
+		dev_err(dev, "Failed to register PHY provider: %ld\n",
+			PTR_ERR(provider));
+		return PTR_ERR(provider);
+	}
+
+	return 0;
+}
+
+static const struct of_device_id cdns_dphy_rx_of_match[] = {
+	{ .compatible = "cdns,dphy-rx" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, cdns_dphy_rx_of_match);
+
+static struct platform_driver cdns_dphy_rx_platform_driver = {
+	.probe		= cdns_dphy_rx_probe,
+	.driver		= {
+		.name		= "cdns-mipi-dphy-rx",
+		.of_match_table	= cdns_dphy_rx_of_match,
+	},
+};
+module_platform_driver(cdns_dphy_rx_platform_driver);
+
+MODULE_AUTHOR("Pratyush Yadav <[e-mail]>");
+MODULE_DESCRIPTION("Cadence D-PHY Rx Driver");
+MODULE_LICENSE("GPL");