sgi_w1.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * sgi_w1.c - w1 master driver for one wire support in SGI ASICs
  4 */
  5
  6#include <linux/clk.h>
  7#include <linux/delay.h>
  8#include <linux/io.h>
  9#include <linux/jiffies.h>
 10#include <linux/module.h>
 11#include <linux/mod_devicetable.h>
 12#include <linux/platform_device.h>
 13#include <linux/platform_data/sgi-w1.h>
 14
 15#include <linux/w1.h>
 16
 17#define MCR_RD_DATA	BIT(0)
 18#define MCR_DONE	BIT(1)
 19
 20#define MCR_PACK(pulse, sample) (((pulse) << 10) | ((sample) << 2))
 21
 22struct sgi_w1_device {
 23	u32 __iomem *mcr;
 24	struct w1_bus_master bus_master;
 25	char dev_id[64];
 26};
 27
 28static u8 sgi_w1_wait(u32 __iomem *mcr)
 29{
 30	u32 mcr_val;
 31
 32	do {
 33		mcr_val = readl(mcr);
 34	} while (!(mcr_val & MCR_DONE));
 35
 36	return (mcr_val & MCR_RD_DATA) ? 1 : 0;
 37}
 38
 39/*
 40 * this is the low level routine to
 41 * reset the device on the One Wire interface
 42 * on the hardware
 43 */
 44static u8 sgi_w1_reset_bus(void *data)
 45{
 46	struct sgi_w1_device *dev = data;
 47	u8 ret;
 48
 49	writel(MCR_PACK(520, 65), dev->mcr);
 50	ret = sgi_w1_wait(dev->mcr);
 51	udelay(500); /* recovery time */
 52	return ret;
 53}
 54
 55/*
 56 * this is the low level routine to read/write a bit on the One Wire
 57 * interface on the hardware. It does write 0 if parameter bit is set
 58 * to 0, otherwise a write 1/read.
 59 */
 60static u8 sgi_w1_touch_bit(void *data, u8 bit)
 61{
 62	struct sgi_w1_device *dev = data;
 63	u8 ret;
 64
 65	if (bit)
 66		writel(MCR_PACK(6, 13), dev->mcr);
 67	else
 68		writel(MCR_PACK(80, 30), dev->mcr);
 69
 70	ret = sgi_w1_wait(dev->mcr);
 71	if (bit)
 72		udelay(100); /* recovery */
 73	return ret;
 74}
 75
 76static int sgi_w1_probe(struct platform_device *pdev)
 77{
 78	struct sgi_w1_device *sdev;
 79	struct sgi_w1_platform_data *pdata;
 80
 81	sdev = devm_kzalloc(&pdev->dev, sizeof(struct sgi_w1_device),
 82			    GFP_KERNEL);
 83	if (!sdev)
 84		return -ENOMEM;
 85
 86	sdev->mcr = devm_platform_ioremap_resource(pdev, 0);
 87	if (IS_ERR(sdev->mcr))
 88		return PTR_ERR(sdev->mcr);
 89
 90	sdev->bus_master.data = sdev;
 91	sdev->bus_master.reset_bus = sgi_w1_reset_bus;
 92	sdev->bus_master.touch_bit = sgi_w1_touch_bit;
 93
 94	pdata = dev_get_platdata(&pdev->dev);
 95	if (pdata) {
 96		strscpy(sdev->dev_id, pdata->dev_id, sizeof(sdev->dev_id));
 97		sdev->bus_master.dev_id = sdev->dev_id;
 98	}
 99
100	platform_set_drvdata(pdev, sdev);
101
102	return w1_add_master_device(&sdev->bus_master);
103}
104
105/*
106 * disassociate the w1 device from the driver
107 */
108static void sgi_w1_remove(struct platform_device *pdev)
109{
110	struct sgi_w1_device *sdev = platform_get_drvdata(pdev);
111
112	w1_remove_master_device(&sdev->bus_master);
113}
114
115static struct platform_driver sgi_w1_driver = {
116	.driver = {
117		.name = "sgi_w1",
118	},
119	.probe = sgi_w1_probe,
120	.remove = sgi_w1_remove,
121};
122module_platform_driver(sgi_w1_driver);
123
124MODULE_LICENSE("GPL");
125MODULE_AUTHOR("Thomas Bogendoerfer");
126MODULE_DESCRIPTION("Driver for One-Wire IP in SGI ASICs");