1 #include <linux/init.h>
2 #include <linux/clocksource.h>
3 #include <linux/clockchips.h>
4 #include <linux/interrupt.h>
5 #include <linux/irq.h>
6
7 #include <linux/clk.h>
8 #include <linux/err.h>
9 #include <linux/ioport.h>
10 #include <linux/io.h>
11 #include <linux/platform_device.h>
12 #include <linux/atmel_tc.h>
13
14
15 /*
16 * We're configured to use a specific TC block, one that's not hooked
17 * up to external hardware, to provide a time solution:
18 *
19 * - Two channels combine to create a free-running 32 bit counter
20 * with a base rate of 5+ MHz, packaged as a clocksource (with
21 * resolution better than 200 nsec).
22 *
23 * - The third channel may be used to provide a 16-bit clockevent
24 * source, used in either periodic or oneshot mode. This runs
25 * at 32 KiHZ, and can handle delays of up to two seconds.
26 *
27 * A boot clocksource and clockevent source are also currently needed,
28 * unless the relevant platforms (ARM/AT91, AVR32/AT32) are changed so
29 * this code can be used when init_timers() is called, well before most
30 * devices are set up. (Some low end AT91 parts, which can run uClinux,
31 * have only the timers in one TC block... they currently don't support
32 * the tclib code, because of that initialization issue.)
33 *
34 * REVISIT behavior during system suspend states... we should disable
35 * all clocks and save the power. Easily done for clockevent devices,
36 * but clocksources won't necessarily get the needed notifications.
37 * For deeper system sleep states, this will be mandatory...
38 */
39
40 static void __iomem *tcaddr;
41
tc_get_cycles(void)42 static cycle_t tc_get_cycles(void)
43 {
44 unsigned long flags;
45 u32 lower, upper;
46
47 raw_local_irq_save(flags);
48 do {
49 upper = __raw_readl(tcaddr + ATMEL_TC_REG(1, CV));
50 lower = __raw_readl(tcaddr + ATMEL_TC_REG(0, CV));
51 } while (upper != __raw_readl(tcaddr + ATMEL_TC_REG(1, CV)));
52
53 raw_local_irq_restore(flags);
54 return (upper << 16) | lower;
55 }
56
57 static struct clocksource clksrc = {
58 .name = "tcb_clksrc",
59 .rating = 200,
60 .read = tc_get_cycles,
61 .mask = CLOCKSOURCE_MASK(32),
62 .shift = 18,
63 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
64 };
65
66 #ifdef CONFIG_GENERIC_CLOCKEVENTS
67
68 struct tc_clkevt_device {
69 struct clock_event_device clkevt;
70 struct clk *clk;
71 void __iomem *regs;
72 };
73
to_tc_clkevt(struct clock_event_device * clkevt)74 static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
75 {
76 return container_of(clkevt, struct tc_clkevt_device, clkevt);
77 }
78
79 /* For now, we always use the 32K clock ... this optimizes for NO_HZ,
80 * because using one of the divided clocks would usually mean the
81 * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
82 *
83 * A divided clock could be good for high resolution timers, since
84 * 30.5 usec resolution can seem "low".
85 */
86 static u32 timer_clock;
87
tc_mode(enum clock_event_mode m,struct clock_event_device * d)88 static void tc_mode(enum clock_event_mode m, struct clock_event_device *d)
89 {
90 struct tc_clkevt_device *tcd = to_tc_clkevt(d);
91 void __iomem *regs = tcd->regs;
92
93 if (tcd->clkevt.mode == CLOCK_EVT_MODE_PERIODIC
94 || tcd->clkevt.mode == CLOCK_EVT_MODE_ONESHOT) {
95 __raw_writel(0xff, regs + ATMEL_TC_REG(2, IDR));
96 __raw_writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
97 clk_disable(tcd->clk);
98 }
99
100 switch (m) {
101
102 /* By not making the gentime core emulate periodic mode on top
103 * of oneshot, we get lower overhead and improved accuracy.
104 */
105 case CLOCK_EVT_MODE_PERIODIC:
106 clk_enable(tcd->clk);
107
108 /* slow clock, count up to RC, then irq and restart */
109 __raw_writel(timer_clock
110 | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
111 regs + ATMEL_TC_REG(2, CMR));
112 __raw_writel((32768 + HZ/2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
113
114 /* Enable clock and interrupts on RC compare */
115 __raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
116
117 /* go go gadget! */
118 __raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
119 regs + ATMEL_TC_REG(2, CCR));
120 break;
121
122 case CLOCK_EVT_MODE_ONESHOT:
123 clk_enable(tcd->clk);
124
125 /* slow clock, count up to RC, then irq and stop */
126 __raw_writel(timer_clock | ATMEL_TC_CPCSTOP
127 | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
128 regs + ATMEL_TC_REG(2, CMR));
129 __raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
130
131 /* set_next_event() configures and starts the timer */
132 break;
133
134 default:
135 break;
136 }
137 }
138
tc_next_event(unsigned long delta,struct clock_event_device * d)139 static int tc_next_event(unsigned long delta, struct clock_event_device *d)
140 {
141 __raw_writel(delta, tcaddr + ATMEL_TC_REG(2, RC));
142
143 /* go go gadget! */
144 __raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
145 tcaddr + ATMEL_TC_REG(2, CCR));
146 return 0;
147 }
148
149 static struct tc_clkevt_device clkevt = {
150 .clkevt = {
151 .name = "tc_clkevt",
152 .features = CLOCK_EVT_FEAT_PERIODIC
153 | CLOCK_EVT_FEAT_ONESHOT,
154 .shift = 32,
155 /* Should be lower than at91rm9200's system timer */
156 .rating = 125,
157 .set_next_event = tc_next_event,
158 .set_mode = tc_mode,
159 },
160 };
161
ch2_irq(int irq,void * handle)162 static irqreturn_t ch2_irq(int irq, void *handle)
163 {
164 struct tc_clkevt_device *dev = handle;
165 unsigned int sr;
166
167 sr = __raw_readl(dev->regs + ATMEL_TC_REG(2, SR));
168 if (sr & ATMEL_TC_CPCS) {
169 dev->clkevt.event_handler(&dev->clkevt);
170 return IRQ_HANDLED;
171 }
172
173 return IRQ_NONE;
174 }
175
176 static struct irqaction tc_irqaction = {
177 .name = "tc_clkevt",
178 .flags = IRQF_TIMER | IRQF_DISABLED,
179 .handler = ch2_irq,
180 };
181
setup_clkevents(struct atmel_tc * tc,int clk32k_divisor_idx)182 static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
183 {
184 struct clk *t2_clk = tc->clk[2];
185 int irq = tc->irq[2];
186
187 clkevt.regs = tc->regs;
188 clkevt.clk = t2_clk;
189 tc_irqaction.dev_id = &clkevt;
190
191 timer_clock = clk32k_divisor_idx;
192
193 clkevt.clkevt.mult = div_sc(32768, NSEC_PER_SEC, clkevt.clkevt.shift);
194 clkevt.clkevt.max_delta_ns
195 = clockevent_delta2ns(0xffff, &clkevt.clkevt);
196 clkevt.clkevt.min_delta_ns = clockevent_delta2ns(1, &clkevt.clkevt) + 1;
197 clkevt.clkevt.cpumask = cpumask_of(0);
198
199 setup_irq(irq, &tc_irqaction);
200
201 clockevents_register_device(&clkevt.clkevt);
202 }
203
204 #else /* !CONFIG_GENERIC_CLOCKEVENTS */
205
setup_clkevents(struct atmel_tc * tc,int clk32k_divisor_idx)206 static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
207 {
208 /* NOTHING */
209 }
210
211 #endif
212
tcb_clksrc_init(void)213 static int __init tcb_clksrc_init(void)
214 {
215 static char bootinfo[] __initdata
216 = KERN_DEBUG "%s: tc%d at %d.%03d MHz\n";
217
218 struct platform_device *pdev;
219 struct atmel_tc *tc;
220 struct clk *t0_clk;
221 u32 rate, divided_rate = 0;
222 int best_divisor_idx = -1;
223 int clk32k_divisor_idx = -1;
224 int i;
225
226 tc = atmel_tc_alloc(CONFIG_ATMEL_TCB_CLKSRC_BLOCK, clksrc.name);
227 if (!tc) {
228 pr_debug("can't alloc TC for clocksource\n");
229 return -ENODEV;
230 }
231 tcaddr = tc->regs;
232 pdev = tc->pdev;
233
234 t0_clk = tc->clk[0];
235 clk_enable(t0_clk);
236
237 /* How fast will we be counting? Pick something over 5 MHz. */
238 rate = (u32) clk_get_rate(t0_clk);
239 for (i = 0; i < 5; i++) {
240 unsigned divisor = atmel_tc_divisors[i];
241 unsigned tmp;
242
243 /* remember 32 KiHz clock for later */
244 if (!divisor) {
245 clk32k_divisor_idx = i;
246 continue;
247 }
248
249 tmp = rate / divisor;
250 pr_debug("TC: %u / %-3u [%d] --> %u\n", rate, divisor, i, tmp);
251 if (best_divisor_idx > 0) {
252 if (tmp < 5 * 1000 * 1000)
253 continue;
254 }
255 divided_rate = tmp;
256 best_divisor_idx = i;
257 }
258
259 clksrc.mult = clocksource_hz2mult(divided_rate, clksrc.shift);
260
261 printk(bootinfo, clksrc.name, CONFIG_ATMEL_TCB_CLKSRC_BLOCK,
262 divided_rate / 1000000,
263 ((divided_rate + 500000) % 1000000) / 1000);
264
265 /* tclib will give us three clocks no matter what the
266 * underlying platform supports.
267 */
268 clk_enable(tc->clk[1]);
269
270 /* channel 0: waveform mode, input mclk/8, clock TIOA0 on overflow */
271 __raw_writel(best_divisor_idx /* likely divide-by-8 */
272 | ATMEL_TC_WAVE
273 | ATMEL_TC_WAVESEL_UP /* free-run */
274 | ATMEL_TC_ACPA_SET /* TIOA0 rises at 0 */
275 | ATMEL_TC_ACPC_CLEAR, /* (duty cycle 50%) */
276 tcaddr + ATMEL_TC_REG(0, CMR));
277 __raw_writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
278 __raw_writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
279 __raw_writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR)); /* no irqs */
280 __raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
281
282 /* channel 1: waveform mode, input TIOA0 */
283 __raw_writel(ATMEL_TC_XC1 /* input: TIOA0 */
284 | ATMEL_TC_WAVE
285 | ATMEL_TC_WAVESEL_UP, /* free-run */
286 tcaddr + ATMEL_TC_REG(1, CMR));
287 __raw_writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR)); /* no irqs */
288 __raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));
289
290 /* chain channel 0 to channel 1, then reset all the timers */
291 __raw_writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
292 __raw_writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
293
294 /* and away we go! */
295 clocksource_register(&clksrc);
296
297 /* channel 2: periodic and oneshot timer support */
298 setup_clkevents(tc, clk32k_divisor_idx);
299
300 return 0;
301 }
302 arch_initcall(tcb_clksrc_init);
303