Message-Id: <20240829105444.2885653-1-carlos.song@nxp.com>
Date: Thu, 29 Aug 2024 18:54:44 +0800
From: carlos.song@....com
To: aisheng.dong@....com,
	andi.shyti@...nel.org,
	shawnguo@...nel.org,
	s.hauer@...gutronix.de,
	kernel@...gutronix.de,
	festevam@...il.com
Cc: linux-i2c@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2] i2c: imx-lpi2c: add target mode support

From: Carlos Song <carlos.song@....com>

Add target mode support for LPI2C.

Signed-off-by: Carlos Song <carlos.song@....com>
---
Change for V2:
- remove unused variable ‘lpi2c_imx’ in lpi2c_suspend_noirq.
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 252 ++++++++++++++++++++++++++++-
 1 file changed, 248 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 530ca5d76403..73eb04c04466 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -43,6 +43,20 @@
 #define LPI2C_MTDR	0x60	/* i2c master TX data register */
 #define LPI2C_MRDR	0x70	/* i2c master RX data register */
 
+#define LPI2C_SCR	0x110	/* i2c target contrl register */
+#define LPI2C_SSR	0x114	/* i2c target status register */
+#define LPI2C_SIER	0x118	/* i2c target interrupt enable */
+#define LPI2C_SDER	0x11C	/* i2c target DMA enable */
+#define LPI2C_SCFGR0	0x120	/* i2c target configuration */
+#define LPI2C_SCFGR1	0x124	/* i2c target configuration */
+#define LPI2C_SCFGR2	0x128	/* i2c target configuration */
+#define LPI2C_SAMR	0x140	/* i2c target address match */
+#define LPI2C_SASR	0x150	/* i2c target address status */
+#define LPI2C_STAR	0x154	/* i2c target transmit ACK */
+#define LPI2C_STDR	0x160	/* i2c target transmit data */
+#define LPI2C_SRDR	0x170	/* i2c target receive data */
+#define LPI2C_SRDROR	0x178	/* i2c target receive data read only */
+
 /* i2c command */
 #define TRAN_DATA	0X00
 #define RECV_DATA	0X01
@@ -76,6 +90,42 @@
 #define MDER_TDDE	BIT(0)
 #define MDER_RDDE	BIT(1)
 
+#define SCR_SEN		BIT(0)
+#define SCR_RST		BIT(1)
+#define SCR_FILTEN	BIT(4)
+#define SCR_RTF		BIT(8)
+#define SCR_RRF		BIT(9)
+#define SCFGR1_RXSTALL	BIT(1)
+#define SCFGR1_TXDSTALL	BIT(2)
+#define SCFGR2_FILTSDA_SHIFT	24
+#define SCFGR2_FILTSCL_SHIFT	16
+#define SCFGR2_CLKHOLD(x)	(x)
+#define SCFGR2_FILTSDA(x)	((x) << SCFGR2_FILTSDA_SHIFT)
+#define SCFGR2_FILTSCL(x)	((x) << SCFGR2_FILTSCL_SHIFT)
+#define SSR_TDF		BIT(0)
+#define SSR_RDF		BIT(1)
+#define SSR_AVF		BIT(2)
+#define SSR_TAF		BIT(3)
+#define SSR_RSF		BIT(8)
+#define SSR_SDF		BIT(9)
+#define SSR_BEF		BIT(10)
+#define SSR_FEF		BIT(11)
+#define SSR_SBF		BIT(24)
+#define SSR_BBF		BIT(25)
+#define SSR_CLEAR_BITS	(SSR_RSF | SSR_SDF | SSR_BEF | SSR_FEF)
+#define SIER_TDIE	BIT(0)
+#define SIER_RDIE	BIT(1)
+#define SIER_AVIE	BIT(2)
+#define SIER_TAIE	BIT(3)
+#define SIER_RSIE	BIT(8)
+#define SIER_SDIE	BIT(9)
+#define SIER_BEIE	BIT(10)
+#define SIER_FEIE	BIT(11)
+#define SIER_AM0F	BIT(12)
+#define SASR_READ_REQ	0x1
+#define SLAVE_INT_FLAG	(SIER_TDIE | SIER_RDIE | SIER_AVIE | \
+						SIER_SDIE | SIER_BEIE)
+
 #define I2C_CLK_RATIO	2
 #define CHUNK_DATA	256
 
@@ -133,6 +183,7 @@ struct lpi2c_imx_struct {
 	struct i2c_bus_recovery_info rinfo;
 	bool			can_use_dma;
 	struct lpi2c_imx_dma	*dma;
+	struct i2c_client	*target;
 };
 
 static void lpi2c_imx_intctrl(struct lpi2c_imx_struct *lpi2c_imx,
@@ -952,9 +1003,57 @@ static int lpi2c_imx_xfer(struct i2c_adapter *adapter,
 	return (result < 0) ? result : num;
 }
 
-static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
+static irqreturn_t lpi2c_imx_target_isr(struct lpi2c_imx_struct *lpi2c_imx,
+					   u32 ssr, u32 sier_filter)
+{
+	u8 value;
+	u32 sasr;
+
+	/* Arbitration lost */
+	if (sier_filter & SSR_BEF) {
+		writel(0, lpi2c_imx->base + LPI2C_SIER);
+		return IRQ_HANDLED;
+	}
+
+	/* Address detected */
+	if (sier_filter & SSR_AVF) {
+		sasr = readl(lpi2c_imx->base + LPI2C_SASR);
+		if (SASR_READ_REQ & sasr) {
+			/* Read request */
+			i2c_slave_event(lpi2c_imx->target, I2C_SLAVE_READ_REQUESTED, &value);
+			writel(value, lpi2c_imx->base + LPI2C_STDR);
+			goto ret;
+		} else {
+			/* Write request */
+			i2c_slave_event(lpi2c_imx->target, I2C_SLAVE_WRITE_REQUESTED, &value);
+		}
+	}
+
+	if (sier_filter & SSR_SDF) {
+		/* STOP */
+		i2c_slave_event(lpi2c_imx->target, I2C_SLAVE_STOP, &value);
+	}
+
+	if (sier_filter & SSR_TDF) {
+		/* Target send data */
+		i2c_slave_event(lpi2c_imx->target, I2C_SLAVE_READ_PROCESSED, &value);
+		writel(value, lpi2c_imx->base + LPI2C_STDR);
+	}
+
+	if (sier_filter & SSR_RDF) {
+		/* Target receive data */
+		value = readl(lpi2c_imx->base + LPI2C_SRDR);
+		i2c_slave_event(lpi2c_imx->target, I2C_SLAVE_WRITE_RECEIVED, &value);
+	}
+
+ret:
+	/* Clear SSR */
+	writel(ssr & SSR_CLEAR_BITS, lpi2c_imx->base + LPI2C_SSR);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t lpi2c_imx_master_isr(struct lpi2c_imx_struct *lpi2c_imx)
 {
-	struct lpi2c_imx_struct *lpi2c_imx = dev_id;
 	unsigned int enabled;
 	unsigned int temp;
 
@@ -974,6 +1073,119 @@ static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
+{
+	struct lpi2c_imx_struct *lpi2c_imx = dev_id;
+	u32 ssr, sier_filter;
+	unsigned int scr;
+
+	if (lpi2c_imx->target) {
+		scr = readl(lpi2c_imx->base + LPI2C_SCR);
+		ssr = readl(lpi2c_imx->base + LPI2C_SSR);
+		sier_filter = ssr & readl(lpi2c_imx->base + LPI2C_SIER);
+		if ((scr & SCR_SEN) && sier_filter)
+			return lpi2c_imx_target_isr(lpi2c_imx, ssr, sier_filter);
+		else
+			return lpi2c_imx_master_isr(lpi2c_imx);
+	} else {
+		return lpi2c_imx_master_isr(lpi2c_imx);
+	}
+}
+
+static void lpi2c_imx_target_init(struct lpi2c_imx_struct *lpi2c_imx)
+{
+	int temp;
+
+	/* reset target module */
+	writel(SCR_RST, lpi2c_imx->base + LPI2C_SCR);
+	writel(0, lpi2c_imx->base + LPI2C_SCR);
+
+	/* Set target addr */
+	writel((lpi2c_imx->target->addr << 1), lpi2c_imx->base + LPI2C_SAMR);
+
+	writel(SCFGR1_RXSTALL | SCFGR1_TXDSTALL, lpi2c_imx->base + LPI2C_SCFGR1);
+
+	/*
+	 * set SCFGR2: FILTSDA, FILTSCL and CLKHOLD
+	 *
+	 * FILTSCL/FILTSDA can eliminate signal skew. It should generally be
+	 * set to the same value and should be set >= 50ns.
+	 *
+	 * CLKHOLD is only used when clock stretching is enabled, but it will
+	 * extend the clock stretching to ensure there is an additional delay
+	 * between the target driving SDA and the target releasing the SCL pin.
+	 *
+	 * CLKHOLD setting is crucial for lpi2c target. When master read data
+	 * from target, if there is a delay caused by cpu idle, excessive load,
+	 * or other delays between two bytes in one message transmission. so it
+	 * will cause a short interval time between the driving SDA signal and
+	 * releasing SCL signal. Lpi2c master will mistakenly think it is a stop
+	 * signal resulting in an arbitration failure. This issue can be avoided
+	 * by setting CLKHOLD.
+	 *
+	 * In order to ensure lpi2c function normally when the lpi2c speed is as
+	 * low as 100kHz, CLKHOLD should be set 3 and it is also compatible with
+	 * higher clock frequency like 400kHz and 1MHz.
+	 */
+	temp = SCFGR2_FILTSDA(2) | SCFGR2_FILTSCL(2) | SCFGR2_CLKHOLD(3);
+	writel(temp, lpi2c_imx->base + LPI2C_SCFGR2);
+
+	/*
+	 * Enable module:
+	 * SCR_FILTEN can enable digital filter and output delay counter for LPI2C
+	 * target mode. So SCR_FILTEN need be asserted when enable SDA/SCL FILTER
+	 * and CLKHOLD.
+	 */
+	writel(SCR_SEN | SCR_FILTEN, lpi2c_imx->base + LPI2C_SCR);
+
+	/* Enable interrupt from i2c module */
+	writel(SLAVE_INT_FLAG, lpi2c_imx->base + LPI2C_SIER);
+}
+
+static int lpi2c_imx_reg_target(struct i2c_client *client)
+{
+	struct lpi2c_imx_struct *lpi2c_imx = i2c_get_adapdata(client->adapter);
+	int ret;
+
+	if (lpi2c_imx->target)
+		return -EBUSY;
+
+	lpi2c_imx->target = client;
+
+	ret = pm_runtime_resume_and_get(lpi2c_imx->adapter.dev.parent);
+	if (ret < 0) {
+		dev_err(&lpi2c_imx->adapter.dev, "failed to resume i2c controller");
+		return ret;
+	}
+
+	lpi2c_imx_target_init(lpi2c_imx);
+
+	return 0;
+}
+
+static int lpi2c_imx_unreg_target(struct i2c_client *client)
+{
+	struct lpi2c_imx_struct *lpi2c_imx = i2c_get_adapdata(client->adapter);
+	int ret;
+
+	if (!lpi2c_imx->target)
+		return -EINVAL;
+
+	/* Reset target address. */
+	writel(0, lpi2c_imx->base + LPI2C_SAMR);
+
+	writel(SCR_RST, lpi2c_imx->base + LPI2C_SCR);
+	writel(0, lpi2c_imx->base + LPI2C_SCR);
+
+	lpi2c_imx->target = NULL;
+
+	ret = pm_runtime_put_sync(lpi2c_imx->adapter.dev.parent);
+	if (ret < 0)
+		dev_err(&lpi2c_imx->adapter.dev, "failed to suspend i2c controller");
+
+	return ret;
+}
+
 static int lpi2c_imx_init_recovery_info(struct lpi2c_imx_struct *lpi2c_imx,
 				  struct platform_device *pdev)
 {
@@ -1049,6 +1261,8 @@ static u32 lpi2c_imx_func(struct i2c_adapter *adapter)
 static const struct i2c_algorithm lpi2c_imx_algo = {
 	.master_xfer	= lpi2c_imx_xfer,
 	.functionality	= lpi2c_imx_func,
+	.reg_slave		= lpi2c_imx_reg_target,
+	.unreg_slave	= lpi2c_imx_unreg_target,
 };
 
 static const struct of_device_id lpi2c_imx_of_match[] = {
@@ -1199,9 +1413,39 @@ static int __maybe_unused lpi2c_runtime_resume(struct device *dev)
 	return 0;
 }
 
+static int lpi2c_suspend_noirq(struct device *dev)
+{
+	int ret;
+
+	ret = pm_runtime_force_suspend(dev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int lpi2c_resume_noirq(struct device *dev)
+{
+	struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
+	int ret;
+
+	ret = pm_runtime_force_resume(dev);
+	if (ret)
+		return ret;
+
+	/*
+	 * If i2c module powered down in system suspend, register
+	 * value will lose. So reinit target when system resume.
+	 */
+	if (lpi2c_imx->target)
+		lpi2c_imx_target_init(lpi2c_imx);
+
+	return 0;
+}
+
 static const struct dev_pm_ops lpi2c_pm_ops = {
-	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
-				      pm_runtime_force_resume)
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(lpi2c_suspend_noirq,
+				      lpi2c_resume_noirq)
 	SET_RUNTIME_PM_OPS(lpi2c_runtime_suspend,
 			   lpi2c_runtime_resume, NULL)
 };
-- 
2.34.1

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