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From:   Kris Chaplin <kris.chaplin@amd.com>
To:     <kris.chaplin@amd.com>, <thomas.delev@amd.com>,
        <michal.simek@amd.com>, <krzysztof.kozlowski@linaro.org>,
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        <git@amd.com>
Subject: [PATCH 2/2] w1: Add 1-wire master driver for AMD programmable logic IP Core
Date:   Fri, 13 Oct 2023 02:30:13 -0700
Message-ID: <20231013093109.37165-3-kris.chaplin@amd.com>
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Add a master driver to support the AMD 1-Wire programmable logic IP block.
This block guarantees protocol timing for driving off-board devices such
as thermal sensors, proms, etc.

Add file to MAINTAINERS

Co-developed-by: Thomas Delev <thomas.delev@amd.com>
Signed-off-by: Thomas Delev <thomas.delev@amd.com>
Signed-off-by: Kris Chaplin <kris.chaplin@amd.com>
---
 MAINTAINERS                 |   1 +
 drivers/w1/masters/Kconfig  |  11 +
 drivers/w1/masters/Makefile |   1 +
 drivers/w1/masters/amd_w1.c | 422 ++++++++++++++++++++++++++++++++++++
 4 files changed, 435 insertions(+)
 create mode 100644 drivers/w1/masters/amd_w1.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 6ec3922b256e..7f26dab5261b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1072,6 +1072,7 @@ R:	Thomas Delev <thomas.delev@amd.com>
 R:	Michal Simek <michal.simek@amd.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/w1/amd,axi-1wire-master.yaml
+F:	drivers/w1/masters/amd_w1.c
 
 AMD XGBE DRIVER
 M:	"Shyam Sundar S K" <Shyam-sundar.S-k@amd.com>
diff --git a/drivers/w1/masters/Kconfig b/drivers/w1/masters/Kconfig
index ad316573288a..9232fd1f4e5b 100644
--- a/drivers/w1/masters/Kconfig
+++ b/drivers/w1/masters/Kconfig
@@ -67,5 +67,16 @@ config W1_MASTER_SGI
 	  This support is also available as a module.  If so, the module
 	  will be called sgi_w1.
 
+config W1_MASTER_AMD
+	tristate "AMD AXI 1-wire bus master"
+	help
+	  Say Y here is you want to support the AMD AXI 1-wire IP core.
+	  This driver makes use of the programmable logic IP to perform
+	  correctly timed 1 wire transactions without relying on GPIO timing
+	  through the kernel.
+
+	  This driver can also be built as a module.  If so, the module will be
+	  called amd_w1.
+
 endmenu
 
diff --git a/drivers/w1/masters/Makefile b/drivers/w1/masters/Makefile
index c5d85a827e52..cd3da1daaf97 100644
--- a/drivers/w1/masters/Makefile
+++ b/drivers/w1/masters/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_W1_MASTER_MXC)		+= mxc_w1.o
 obj-$(CONFIG_W1_MASTER_GPIO)		+= w1-gpio.o
 obj-$(CONFIG_HDQ_MASTER_OMAP)		+= omap_hdq.o
 obj-$(CONFIG_W1_MASTER_SGI)		+= sgi_w1.o
+obj-$(CONFIG_W1_MASTER_AMD)		+= amd_w1.o
diff --git a/drivers/w1/masters/amd_w1.c b/drivers/w1/masters/amd_w1.c
new file mode 100644
index 000000000000..04bf08c1b6d7
--- /dev/null
+++ b/drivers/w1/masters/amd_w1.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * amd_w1 - AMD 1Wire bus master driver
+ *
+ * Copyright (C) 2022-2023 Advanced Micro Devices, Inc. All Rights Reserved.
+ */
+
+#include <linux/atomic.h>
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+
+#include <linux/w1.h>
+
+/* 1-wire AMD IP definition */
+#define AXIW1_IPID	0x10ee4453
+/* Registers offset */
+#define AXIW1_INST_REG	0x0
+#define AXIW1_CTRL_REG	0x4
+#define AXIW1_IRQE_REG	0x8
+#define AXIW1_STAT_REG	0xC
+#define AXIW1_DATA_REG	0x10
+#define AXIW1_IPVER_REG	0x18
+#define AXIW1_IPID_REG	0x1C
+/* Instructions */
+#define AXIW1_INITPRES	0x0800
+#define AXIW1_READBIT	0x0C00
+#define AXIW1_WRITEBIT	0x0E00
+#define AXIW1_READBYTE	0x0D00
+#define AXIW1_WRITEBYTE	0x0F00
+/* Status flag masks */
+#define AXIW1_DONE	BIT(0)
+#define AXIW1_READY	BIT(4)
+#define AXIW1_PRESENCE	BIT(31)
+#define AXIW1_MAJORVER_MASK	GENMASK(23, 8)
+#define AXIW1_MINORVER_MASK	GENMASK(7, 0)
+/* Control flag */
+#define AXIW1_GO	BIT(0)
+#define AXI_CLEAR	0
+#define AXI_RESET	BIT(31)
+#define AXIW1_READDATA	BIT(0)
+/* Interrupt Enable */
+#define AXIW1_READY_IRQ_EN	BIT(4)
+#define AXIW1_DONE_IRQ_EN	BIT(0)
+
+#define AXIW1_TIMEOUT	msecs_to_jiffies(100)
+
+#define DRIVER_NAME	"amd_w1"
+
+struct amd_w1_local {
+	struct device *dev;
+	void __iomem *base_addr;
+	int irq;
+	atomic_t flag;
+	struct clk *clk;
+	wait_queue_head_t wait_queue;
+};
+
+/**
+ * amd_w1_write_register() - Helper to write a hardware register.
+ *
+ * @amd_w1_local:	Pointer to device structure
+ * @reg_offset:		Register offset in bytes to write
+ * @val:		Value to write
+ */
+static inline void amd_w1_write_register(struct amd_w1_local *amd_w1_local,
+					 u8 reg_offset, u32 val)
+{
+	iowrite32(val, amd_w1_local->base_addr + reg_offset);
+};
+
+/**
+ * amd_w1_read_register() - Helper to write a hardware register.
+ *
+ * @amd_w1_local:	Pointer to device structure
+ * @reg_offset:		Register offset in bytes to write
+ *
+ * Return:		Value of register read
+ */
+static inline u32 amd_w1_read_register(struct amd_w1_local *amd_w1_local, u8 reg_offset)
+{
+	return ioread32(amd_w1_local->base_addr + reg_offset);
+};
+
+/**
+ * amd_w1_wait_irq_interruptible_timeout() - Wait for IRQ with timeout.
+ *
+ * @amd_w1_local:	Pointer to device structure
+ * @IRQ:		IRQ channel to wait on
+ *
+ * Return:		%0 - OK, %-EINTR - Interrupted, %-EBUSY - Timed out
+ */
+static inline int amd_w1_wait_irq_interruptible_timeout(struct amd_w1_local *amd_w1_local, u32 IRQ)
+{
+	int ret;
+
+	/* Enable the IRQ requested and wait for flag to indicate it's been triggered */
+	amd_w1_write_register(amd_w1_local, AXIW1_IRQE_REG, IRQ);
+	ret = wait_event_interruptible_timeout(amd_w1_local->wait_queue,
+					       atomic_read(&amd_w1_local->flag) != 0,
+					       AXIW1_TIMEOUT);
+	if (ret < 0) {
+		dev_err(amd_w1_local->dev, "Wait IRQ Interrupted\n");
+		return -EINTR;
+	}
+
+	if (!ret) {
+		dev_err(amd_w1_local->dev, "Wait IRQ Timeout\n");
+		return -EBUSY;
+	}
+
+	/* Clear flag */
+	atomic_set(&amd_w1_local->flag, 0);
+	return 0;
+}
+
+/**
+ * amd_w1_touch_bit() - Performs the touch-bit function, which writes a 0 or 1 and reads the level.
+ *
+ * @data:	Pointer to device structure
+ * @bit:	The level to write
+ *
+ * Return:	The level read
+ */
+static u8 amd_w1_touch_bit(void *data, u8 bit)
+{
+	struct amd_w1_local *amd_w1_local = data;
+	u8 val = 0;
+	int rc;
+
+	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_READY) == 0) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_READY_IRQ_EN);
+		if (rc < 0)
+			return 1; /* Callee doesn't test for error. Return inactive bus state */
+	}
+
+	if (bit)
+		/* Read. Write read Bit command in register 0 */
+		amd_w1_write_register(amd_w1_local, AXIW1_INST_REG, AXIW1_READBIT);
+	else
+		/* Write. Write tx Bit command in instruction register with bit to transmit */
+		amd_w1_write_register(amd_w1_local, AXIW1_INST_REG,
+				      (AXIW1_WRITEBIT + (bit & 0x01)));
+
+	/* Write Go signal and clear control reset signal in control register */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXIW1_GO);
+
+	/* Wait for done signal to be 1 */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_DONE_IRQ_EN);
+		if (rc < 0)
+			return 1; /* Callee doesn't test for error. Return inactive bus state */
+	}
+
+	/* If read, Retrieve data from register */
+	if (bit)
+		val = (u8)(amd_w1_read_register(amd_w1_local, AXIW1_DATA_REG) & AXIW1_READDATA);
+
+	/* Clear Go signal in register 1 */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXI_CLEAR);
+
+	return val;
+}
+
+/**
+ * amd_w1_read_byte - Performs the read byte function.
+ *
+ * @data:	Pointer to device structure
+ * Return:	The value read
+ */
+static u8 amd_w1_read_byte(void *data)
+{
+	struct amd_w1_local *amd_w1_local = data;
+	u8 val = 0;
+	int rc;
+
+	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_READY) == 0) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_READY_IRQ_EN);
+		if (rc < 0)
+			return 0xFF; /* Return inactive bus state */
+	}
+
+	/* Write read Byte command in instruction register*/
+	amd_w1_write_register(amd_w1_local, AXIW1_INST_REG, AXIW1_READBYTE);
+	/* Write Go signal and clear control reset signal in control register */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXIW1_GO);
+
+	/* Wait for done signal to be 1 */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_DONE_IRQ_EN);
+		if (rc < 0)
+			return 0xFF; /* Return inactive bus state */
+	}
+
+	/* Retrieve LSB bit in data register to get RX byte */
+	val = (u8)(amd_w1_read_register(amd_w1_local, AXIW1_DATA_REG) & 0x000000FF);
+
+	/* Clear Go signal in control register */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXI_CLEAR);
+
+	return val;
+}
+
+/**
+ * amd_w1_write_byte - Performs the write byte function.
+ *
+ * @data:	The ds2482 channel pointer
+ * @val:	The value to write
+ */
+static void amd_w1_write_byte(void *data, u8 val)
+{
+	struct amd_w1_local *amd_w1_local = data;
+	int rc;
+
+	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_READY) == 0) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_READY_IRQ_EN);
+		if (rc < 0)
+			return;
+	}
+
+	/* Write tx Byte command in instruction register with bit to transmit */
+	amd_w1_write_register(amd_w1_local, AXIW1_INST_REG, (AXIW1_WRITEBYTE + val));
+	/* Write Go signal and clear control reset signal in register 1 */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXIW1_GO);
+
+	/* Wait for done signal to be 1 */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_DONE_IRQ_EN);
+		if (rc < 0)
+			return;
+	}
+
+	/* Clear Go signal in control register */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXI_CLEAR);
+}
+
+/**
+ * amd_w1_reset_bus() - Issues a reset bus sequence.
+ *
+ * @data:	the bus master data struct
+ * Return:	0=Device present, 1=No device present or error
+ */
+static u8 amd_w1_reset_bus(void *data)
+{
+	struct amd_w1_local *amd_w1_local = data;
+	u8 val = 0;
+	int rc;
+
+	/* Reset 1-wire Axi IP */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXI_RESET);
+
+	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_READY) == 0) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_READY_IRQ_EN);
+		if (rc < 0)
+			return 1; /* Something went wrong with the hardware */
+	}
+	/* Write Initialization command in instruction register */
+	amd_w1_write_register(amd_w1_local, AXIW1_INST_REG, AXIW1_INITPRES);
+	/* Write Go signal and clear control reset signal in register 1 */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXIW1_GO);
+
+	/* Wait for done signal to be 1 */
+	while ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
+		rc = amd_w1_wait_irq_interruptible_timeout(amd_w1_local, AXIW1_DONE_IRQ_EN);
+		if (rc < 0)
+			return 1; /* Something went wrong with the hardware */
+	}
+	/* Retrieve MSB bit in status register to get failure bit */
+	if ((amd_w1_read_register(amd_w1_local, AXIW1_STAT_REG) & AXIW1_PRESENCE) != 0)
+		val = 1;
+
+	/* Clear Go signal in control register */
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXI_CLEAR);
+
+	return val;
+}
+
+/* 1-wire master structure */
+static struct w1_bus_master amd_w1_master = {
+	.touch_bit	= amd_w1_touch_bit,
+	.read_byte	= amd_w1_read_byte,
+	.write_byte	= amd_w1_write_byte,
+	.reset_bus	= amd_w1_reset_bus,
+};
+
+/* Reset the 1-wire AXI IP. Put the IP in reset state and clear registers */
+static void amd_w1_reset(struct amd_w1_local *amd_w1_local)
+{
+	amd_w1_write_register(amd_w1_local, AXIW1_CTRL_REG, AXI_RESET);
+	amd_w1_write_register(amd_w1_local, AXIW1_INST_REG, AXI_CLEAR);
+	amd_w1_write_register(amd_w1_local, AXIW1_IRQE_REG, AXI_CLEAR);
+	amd_w1_write_register(amd_w1_local, AXIW1_STAT_REG, AXI_CLEAR);
+	amd_w1_write_register(amd_w1_local, AXIW1_DATA_REG, AXI_CLEAR);
+}
+
+static irqreturn_t amd_w1_irq(int irq, void *lp)
+{
+	struct amd_w1_local *amd_w1_local = lp;
+
+	/* Clear enables in IRQ enable register */
+	amd_w1_write_register(amd_w1_local, AXIW1_IRQE_REG, AXI_CLEAR);
+
+	/* Wake up the waiting queue */
+	atomic_set(&amd_w1_local->flag, 1);
+	wake_up_interruptible(&amd_w1_local->wait_queue);
+
+	return IRQ_HANDLED;
+}
+
+static int amd_w1_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct amd_w1_local *lp;
+	u32 ver_major, ver_minor;
+	int val, rc = 0;
+
+	/* Get iospace for the device */
+	lp = devm_kzalloc(dev, sizeof(*lp), GFP_KERNEL);
+	if (!lp)
+		return -ENOMEM;
+
+	lp->dev = dev;
+	lp->base_addr = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(lp->base_addr))
+		return PTR_ERR(lp->base_addr);
+
+	/* Get IRQ for the device */
+	lp->irq = platform_get_irq(pdev, 0);
+	if (lp->irq <= 0)
+		return lp->irq;
+
+	rc = devm_request_irq(dev, lp->irq, &amd_w1_irq, IRQF_TRIGGER_HIGH, DRIVER_NAME, lp);
+	if (rc) {
+		dev_err(dev, "Could not allocate interrupt %d.\n", lp->irq);
+		return rc;
+	}
+
+	/* Initialize wait queue and flag */
+	init_waitqueue_head(&lp->wait_queue);
+
+	lp->clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(lp->clk))
+		return PTR_ERR(lp->clk);
+
+	/* Verify IP presence in HW */
+	if (amd_w1_read_register(lp, AXIW1_IPID_REG) != AXIW1_IPID) {
+		dev_err(dev, "AMD 1-wire IP not detected in hardware\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * Allow for future driver expansion supporting new hardware features
+	 * This driver currently only supports hardware 1.x, but include logic
+	 * to detect if a potentially incompatible future version is used
+	 * by reading major version ID. It is highly undesirable for new IP versions
+	 * to break the API, but this code will at least allow for graceful failure
+	 * should that happen. Future new features can be enabled by hardware
+	 * incrementing the minor version and augmenting the driver to detect capability
+	 * using the minor version number
+	 */
+	val = amd_w1_read_register(lp, AXIW1_IPVER_REG);
+	ver_major = FIELD_GET(AXIW1_MAJORVER_MASK, val);
+	ver_minor = FIELD_GET(AXIW1_MINORVER_MASK, val);
+
+	if (ver_major != 1) {
+		dev_err(dev, "AMD AXI W1 Master version %u.%u is not supported by this driver",
+			ver_major, ver_minor);
+		return -ENODEV;
+	}
+
+	amd_w1_master.data = (void *)lp;
+	amd_w1_reset(lp);
+
+	platform_set_drvdata(pdev, lp);
+	rc = w1_add_master_device(&amd_w1_master);
+	if (rc) {
+		dev_err(dev, "Could not add master device\n");
+		amd_w1_reset(lp);
+		return rc;
+	}
+
+	return 0;
+}
+
+static void amd_w1_remove(struct platform_device *pdev)
+{
+	struct amd_w1_local *lp = platform_get_drvdata(pdev);
+
+	w1_remove_master_device(&amd_w1_master);
+	clk_disable_unprepare(lp->clk);
+}
+
+static const struct of_device_id amd_w1_of_match[] = {
+	{ .compatible = "amd,axi-1wire-master" },
+	{ /* end of list */ },
+};
+MODULE_DEVICE_TABLE(of, amd_w1_of_match);
+
+static struct platform_driver amd_w1_driver = {
+	.probe = amd_w1_probe,
+	.remove_new = amd_w1_remove,
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = amd_w1_of_match,
+	},
+};
+module_platform_driver(amd_w1_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Kris Chaplin <kris.chaplin@amd.com>");
+MODULE_DESCRIPTION("Driver for AMD AXI 1 Wire IP core");
-- 
2.42.GIT