1 /*
2  * Copyright (C) 2014 Oleksij Rempel <linux@rempel-privat.de>
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation; either version 2
7  * of the License, or (at your option) any later version.
8  */
9 
10 #include <linux/kernel.h>
11 #include <linux/init.h>
12 #include <linux/interrupt.h>
13 #include <linux/sched.h>
14 #include <linux/clk.h>
15 #include <linux/clocksource.h>
16 #include <linux/clockchips.h>
17 #include <linux/io.h>
18 #include <linux/of.h>
19 #include <linux/of_address.h>
20 #include <linux/of_irq.h>
21 #include <linux/bitops.h>
22 
23 #define DRIVER_NAME	"asm9260-timer"
24 
25 /*
26  * this device provide 4 offsets for each register:
27  * 0x0 - plain read write mode
28  * 0x4 - set mode, OR logic.
29  * 0x8 - clr mode, XOR logic.
30  * 0xc - togle mode.
31  */
32 #define SET_REG 4
33 #define CLR_REG 8
34 
35 #define HW_IR           0x0000 /* RW. Interrupt */
36 #define BM_IR_CR0	BIT(4)
37 #define BM_IR_MR3	BIT(3)
38 #define BM_IR_MR2	BIT(2)
39 #define BM_IR_MR1	BIT(1)
40 #define BM_IR_MR0	BIT(0)
41 
42 #define HW_TCR		0x0010 /* RW. Timer controller */
43 /* BM_C*_RST
44  * Timer Counter and the Prescale Counter are synchronously reset on the
45  * next positive edge of PCLK. The counters remain reset until TCR[1] is
46  * returned to zero. */
47 #define BM_C3_RST	BIT(7)
48 #define BM_C2_RST	BIT(6)
49 #define BM_C1_RST	BIT(5)
50 #define BM_C0_RST	BIT(4)
51 /* BM_C*_EN
52  * 1 - Timer Counter and Prescale Counter are enabled for counting
53  * 0 - counters are disabled */
54 #define BM_C3_EN	BIT(3)
55 #define BM_C2_EN	BIT(2)
56 #define BM_C1_EN	BIT(1)
57 #define BM_C0_EN	BIT(0)
58 
59 #define HW_DIR		0x0020 /* RW. Direction? */
60 /* 00 - count up
61  * 01 - count down
62  * 10 - ?? 2^n/2 */
63 #define BM_DIR_COUNT_UP		0
64 #define BM_DIR_COUNT_DOWN	1
65 #define BM_DIR0_SHIFT	0
66 #define BM_DIR1_SHIFT	4
67 #define BM_DIR2_SHIFT	8
68 #define BM_DIR3_SHIFT	12
69 #define BM_DIR_DEFAULT		(BM_DIR_COUNT_UP << BM_DIR0_SHIFT | \
70 				 BM_DIR_COUNT_UP << BM_DIR1_SHIFT | \
71 				 BM_DIR_COUNT_UP << BM_DIR2_SHIFT | \
72 				 BM_DIR_COUNT_UP << BM_DIR3_SHIFT)
73 
74 #define HW_TC0		0x0030 /* RO. Timer counter 0 */
75 /* HW_TC*. Timer counter owerflow (0xffff.ffff to 0x0000.0000) do not generate
76  * interrupt. This registers can be used to detect overflow */
77 #define HW_TC1          0x0040
78 #define HW_TC2		0x0050
79 #define HW_TC3		0x0060
80 
81 #define HW_PR		0x0070 /* RW. prescaler */
82 #define BM_PR_DISABLE	0
83 #define HW_PC		0x0080 /* RO. Prescaler counter */
84 #define HW_MCR		0x0090 /* RW. Match control */
85 /* enable interrupt on match */
86 #define BM_MCR_INT_EN(n)	(1 << (n * 3 + 0))
87 /* enable TC reset on match */
88 #define BM_MCR_RES_EN(n)	(1 << (n * 3 + 1))
89 /* enable stop TC on match */
90 #define BM_MCR_STOP_EN(n)	(1 << (n * 3 + 2))
91 
92 #define HW_MR0		0x00a0 /* RW. Match reg */
93 #define HW_MR1		0x00b0
94 #define HW_MR2		0x00C0
95 #define HW_MR3		0x00D0
96 
97 #define HW_CTCR		0x0180 /* Counter control */
98 #define BM_CTCR0_SHIFT	0
99 #define BM_CTCR1_SHIFT	2
100 #define BM_CTCR2_SHIFT	4
101 #define BM_CTCR3_SHIFT	6
102 #define BM_CTCR_TM	0	/* Timer mode. Every rising PCLK edge. */
103 #define BM_CTCR_DEFAULT	(BM_CTCR_TM << BM_CTCR0_SHIFT | \
104 			 BM_CTCR_TM << BM_CTCR1_SHIFT | \
105 			 BM_CTCR_TM << BM_CTCR2_SHIFT | \
106 			 BM_CTCR_TM << BM_CTCR3_SHIFT)
107 
108 static struct asm9260_timer_priv {
109 	void __iomem *base;
110 	unsigned long ticks_per_jiffy;
111 } priv;
112 
113 static int asm9260_timer_set_next_event(unsigned long delta,
114 					 struct clock_event_device *evt)
115 {
116 	/* configure match count for TC0 */
117 	writel_relaxed(delta, priv.base + HW_MR0);
118 	/* enable TC0 */
119 	writel_relaxed(BM_C0_EN, priv.base + HW_TCR + SET_REG);
120 	return 0;
121 }
122 
123 static inline void __asm9260_timer_shutdown(struct clock_event_device *evt)
124 {
125 	/* stop timer0 */
126 	writel_relaxed(BM_C0_EN, priv.base + HW_TCR + CLR_REG);
127 }
128 
129 static int asm9260_timer_shutdown(struct clock_event_device *evt)
130 {
131 	__asm9260_timer_shutdown(evt);
132 	return 0;
133 }
134 
135 static int asm9260_timer_set_oneshot(struct clock_event_device *evt)
136 {
137 	__asm9260_timer_shutdown(evt);
138 
139 	/* enable reset and stop on match */
140 	writel_relaxed(BM_MCR_RES_EN(0) | BM_MCR_STOP_EN(0),
141 		       priv.base + HW_MCR + SET_REG);
142 	return 0;
143 }
144 
145 static int asm9260_timer_set_periodic(struct clock_event_device *evt)
146 {
147 	__asm9260_timer_shutdown(evt);
148 
149 	/* disable reset and stop on match */
150 	writel_relaxed(BM_MCR_RES_EN(0) | BM_MCR_STOP_EN(0),
151 		       priv.base + HW_MCR + CLR_REG);
152 	/* configure match count for TC0 */
153 	writel_relaxed(priv.ticks_per_jiffy, priv.base + HW_MR0);
154 	/* enable TC0 */
155 	writel_relaxed(BM_C0_EN, priv.base + HW_TCR + SET_REG);
156 	return 0;
157 }
158 
159 static struct clock_event_device event_dev = {
160 	.name			= DRIVER_NAME,
161 	.rating			= 200,
162 	.features		= CLOCK_EVT_FEAT_PERIODIC |
163 				  CLOCK_EVT_FEAT_ONESHOT,
164 	.set_next_event		= asm9260_timer_set_next_event,
165 	.set_state_shutdown	= asm9260_timer_shutdown,
166 	.set_state_periodic	= asm9260_timer_set_periodic,
167 	.set_state_oneshot	= asm9260_timer_set_oneshot,
168 	.tick_resume		= asm9260_timer_shutdown,
169 };
170 
171 static irqreturn_t asm9260_timer_interrupt(int irq, void *dev_id)
172 {
173 	struct clock_event_device *evt = dev_id;
174 
175 	evt->event_handler(evt);
176 
177 	writel_relaxed(BM_IR_MR0, priv.base + HW_IR);
178 
179 	return IRQ_HANDLED;
180 }
181 
182 /*
183  * ---------------------------------------------------------------------------
184  * Timer initialization
185  * ---------------------------------------------------------------------------
186  */
187 static int __init asm9260_timer_init(struct device_node *np)
188 {
189 	int irq;
190 	struct clk *clk;
191 	int ret;
192 	unsigned long rate;
193 
194 	priv.base = of_io_request_and_map(np, 0, np->name);
195 	if (IS_ERR(priv.base)) {
196 		pr_err("%s: unable to map resource\n", np->name);
197 		return PTR_ERR(priv.base);
198 	}
199 
200 	clk = of_clk_get(np, 0);
201 
202 	ret = clk_prepare_enable(clk);
203 	if (ret) {
204 		pr_err("Failed to enable clk!\n");
205 		return ret;
206 	}
207 
208 	irq = irq_of_parse_and_map(np, 0);
209 	ret = request_irq(irq, asm9260_timer_interrupt, IRQF_TIMER,
210 			DRIVER_NAME, &event_dev);
211 	if (ret) {
212 		pr_err("Failed to setup irq!\n");
213 		return ret;
214 	}
215 
216 	/* set all timers for count-up */
217 	writel_relaxed(BM_DIR_DEFAULT, priv.base + HW_DIR);
218 	/* disable divider */
219 	writel_relaxed(BM_PR_DISABLE, priv.base + HW_PR);
220 	/* make sure all timers use every rising PCLK edge. */
221 	writel_relaxed(BM_CTCR_DEFAULT, priv.base + HW_CTCR);
222 	/* enable interrupt for TC0 and clean setting for all other lines */
223 	writel_relaxed(BM_MCR_INT_EN(0) , priv.base + HW_MCR);
224 
225 	rate = clk_get_rate(clk);
226 	clocksource_mmio_init(priv.base + HW_TC1, DRIVER_NAME, rate,
227 			200, 32, clocksource_mmio_readl_up);
228 
229 	/* Seems like we can't use counter without match register even if
230 	 * actions for MR are disabled. So, set MR to max value. */
231 	writel_relaxed(0xffffffff, priv.base + HW_MR1);
232 	/* enable TC1 */
233 	writel_relaxed(BM_C1_EN, priv.base + HW_TCR + SET_REG);
234 
235 	priv.ticks_per_jiffy = DIV_ROUND_CLOSEST(rate, HZ);
236 	event_dev.cpumask = cpumask_of(0);
237 	clockevents_config_and_register(&event_dev, rate, 0x2c00, 0xfffffffe);
238 
239 	return 0;
240 }
241 TIMER_OF_DECLARE(asm9260_timer, "alphascale,asm9260-timer",
242 		asm9260_timer_init);
243