Re: [PATCH 2/2] w1: Add 1-wire master driver for AMD programmable logic IP Core

From: Krzysztof Kozlowski
Date: Fri Oct 13 2023 - 11:20:21 EST

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In reply to: Kris Chaplin: "[PATCH 2/2] w1: Add 1-wire master driver for AMD programmable logic IP Core"
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On 13/10/2023 11:30, Kris Chaplin wrote:
> 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@xxxxxxx>
> Signed-off-by: Thomas Delev <thomas.delev@xxxxxxx>
> Signed-off-by: Kris Chaplin <kris.chaplin@xxxxxxx>
> ---
> 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@xxxxxxx>
> R: Michal Simek <michal.simek@xxxxxxx>
> 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@xxxxxxx>
> 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

This looks oddly places. Isn't entry above 'S', so A should go before?
The rule is for entire Linux kernel: do not stuff things to the end of
the lists.

> + 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;

Document what this flag does and what its purpose.

> + struct clk *clk;

Why do you need this? It's never changed (after fixing the bug).

> + 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);

Unwrapped code:
iowrite32(IRQ, amd_w1_local->base_addr + AXIW1_IRQE_REG);

Your wrapper:
amd_w1_write_register(amd_w1_local, AXIW1_IRQE_REG, IRQ);

Does not look simpler. If you want to use wrappers, they should actually
help.

> +};
> +
> +/**
> + * 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)

Drop inline.
This does not look like wrapped according to Linux coding convention.
Please abide by the convention, so wrap at 80.

> +{
> + 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 */

Drop.

> + 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 = {

And how does it work with two devices?

> + .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 */

I don't understand this comment.

> + amd_w1_write_register(amd_w1_local, AXIW1_IRQE_REG, AXI_CLEAR);
> +
> + /* Wake up the waiting queue */

Drop obvious comments.

> + 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 */

This is memory allocation, not IO space.

> + 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 */

Drop obvious comments.

> + lp->irq = platform_get_irq(pdev, 0);
> + if (lp->irq <= 0)

Open platform_get_irq() function and read the help. Error handling
couldn't be more explicit there...

> + 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 dev_err_probe(). But this leads us to second question: why would
you notify about allocation errors? Core does it. Do you mean request?

> + 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);

Why? Does this mean that w1_add_master_device() changes the state of
hardware?

> + 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);

This wasn't tested. Duplicated disable.

> +}
> +
> +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@xxxxxxx>");
> +MODULE_DESCRIPTION("Driver for AMD AXI 1 Wire IP core");

Best regards,
Krzysztof

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In reply to: Kris Chaplin: "[PATCH 2/2] w1: Add 1-wire master driver for AMD programmable logic IP Core"
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