1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com>
4 *
5 * Limitations:
6 * - When changing both duty cycle and period, we may end up with one cycle
7 * with the old duty cycle and the new period. This is because the counters
8 * may only be reloaded by first stopping them, or by letting them be
9 * automatically reloaded at the end of a cycle. If this automatic reload
10 * happens after we set TLR0 but before we set TLR1 then we will have a
11 * bad cycle. This could probably be fixed by reading TCR0 just before
12 * reprogramming, but I think it would add complexity for little gain.
13 * - Cannot produce 100% duty cycle by configuring the TLRs. This might be
14 * possible by stopping the counters at an appropriate point in the cycle,
15 * but this is not (yet) implemented.
16 * - Only produces "normal" output.
17 * - Always produces low output if disabled.
18 */
19
20 #include <clocksource/timer-xilinx.h>
21 #include <linux/clk.h>
22 #include <linux/clk-provider.h>
23 #include <linux/device.h>
24 #include <linux/module.h>
25 #include <linux/of.h>
26 #include <linux/platform_device.h>
27 #include <linux/pwm.h>
28 #include <linux/regmap.h>
29
30 /*
31 * The following functions are "common" to drivers for this device, and may be
32 * exported at a future date.
33 */
xilinx_timer_tlr_cycles(struct xilinx_timer_priv * priv,u32 tcsr,u64 cycles)34 u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr,
35 u64 cycles)
36 {
37 WARN_ON(cycles < 2 || cycles - 2 > priv->max);
38
39 if (tcsr & TCSR_UDT)
40 return cycles - 2;
41 return priv->max - cycles + 2;
42 }
43
xilinx_timer_get_period(struct xilinx_timer_priv * priv,u32 tlr,u32 tcsr)44 unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv,
45 u32 tlr, u32 tcsr)
46 {
47 u64 cycles;
48
49 if (tcsr & TCSR_UDT)
50 cycles = tlr + 2;
51 else
52 cycles = (u64)priv->max - tlr + 2;
53
54 /* cycles has a max of 2^32 + 2, so we can't overflow */
55 return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC,
56 clk_get_rate(priv->clk));
57 }
58
59 /*
60 * The idea here is to capture whether the PWM is actually running (e.g.
61 * because we or the bootloader set it up) and we need to be careful to ensure
62 * we don't cause a glitch. According to the data sheet, to enable the PWM we
63 * need to
64 *
65 * - Set both timers to generate mode (MDT=1)
66 * - Set both timers to PWM mode (PWMA=1)
67 * - Enable the generate out signals (GENT=1)
68 *
69 * In addition,
70 *
71 * - The timer must be running (ENT=1)
72 * - The timer must auto-reload TLR into TCR (ARHT=1)
73 * - We must not be in the process of loading TLR into TCR (LOAD=0)
74 * - Cascade mode must be disabled (CASC=0)
75 *
76 * If any of these differ from usual, then the PWM is either disabled, or is
77 * running in a mode that this driver does not support.
78 */
79 #define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA)
80 #define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD)
81 #define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR)
82
83 struct xilinx_pwm_device {
84 struct pwm_chip chip;
85 struct xilinx_timer_priv priv;
86 };
87
88 static inline struct xilinx_timer_priv
xilinx_pwm_chip_to_priv(struct pwm_chip * chip)89 *xilinx_pwm_chip_to_priv(struct pwm_chip *chip)
90 {
91 return &container_of(chip, struct xilinx_pwm_device, chip)->priv;
92 }
93
xilinx_timer_pwm_enabled(u32 tcsr0,u32 tcsr1)94 static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1)
95 {
96 return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET &&
97 (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET;
98 }
99
xilinx_pwm_apply(struct pwm_chip * chip,struct pwm_device * unused,const struct pwm_state * state)100 static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused,
101 const struct pwm_state *state)
102 {
103 struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip);
104 u32 tlr0, tlr1, tcsr0, tcsr1;
105 u64 period_cycles, duty_cycles;
106 unsigned long rate;
107
108 if (state->polarity != PWM_POLARITY_NORMAL)
109 return -EINVAL;
110
111 /*
112 * To be representable by TLR, cycles must be between 2 and
113 * priv->max + 2. To enforce this we can reduce the cycles, but we may
114 * not increase them. Caveat emptor: while this does result in more
115 * predictable rounding, it may also result in a completely different
116 * duty cycle (% high time) than what was requested.
117 */
118 rate = clk_get_rate(priv->clk);
119 /* Avoid overflow */
120 period_cycles = min_t(u64, state->period, U32_MAX * NSEC_PER_SEC);
121 period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC);
122 period_cycles = min_t(u64, period_cycles, priv->max + 2);
123 if (period_cycles < 2)
124 return -ERANGE;
125
126 /* Same thing for duty cycles */
127 duty_cycles = min_t(u64, state->duty_cycle, U32_MAX * NSEC_PER_SEC);
128 duty_cycles = mul_u64_u32_div(duty_cycles, rate, NSEC_PER_SEC);
129 duty_cycles = min_t(u64, duty_cycles, priv->max + 2);
130
131 /*
132 * If we specify 100% duty cycle, we will get 0% instead, so decrease
133 * the duty cycle count by one.
134 */
135 if (duty_cycles >= period_cycles)
136 duty_cycles = period_cycles - 1;
137
138 /* Round down to 0% duty cycle for unrepresentable duty cycles */
139 if (duty_cycles < 2)
140 duty_cycles = period_cycles;
141
142 regmap_read(priv->map, TCSR0, &tcsr0);
143 regmap_read(priv->map, TCSR1, &tcsr1);
144 tlr0 = xilinx_timer_tlr_cycles(priv, tcsr0, period_cycles);
145 tlr1 = xilinx_timer_tlr_cycles(priv, tcsr1, duty_cycles);
146 regmap_write(priv->map, TLR0, tlr0);
147 regmap_write(priv->map, TLR1, tlr1);
148
149 if (state->enabled) {
150 /*
151 * If the PWM is already running, then the counters will be
152 * reloaded at the end of the current cycle.
153 */
154 if (!xilinx_timer_pwm_enabled(tcsr0, tcsr1)) {
155 /* Load TLR into TCR */
156 regmap_write(priv->map, TCSR0, tcsr0 | TCSR_LOAD);
157 regmap_write(priv->map, TCSR1, tcsr1 | TCSR_LOAD);
158 /* Enable timers all at once with ENALL */
159 tcsr0 = (TCSR_PWM_SET & ~TCSR_ENT) | (tcsr0 & TCSR_UDT);
160 tcsr1 = TCSR_PWM_SET | TCSR_ENALL | (tcsr1 & TCSR_UDT);
161 regmap_write(priv->map, TCSR0, tcsr0);
162 regmap_write(priv->map, TCSR1, tcsr1);
163 }
164 } else {
165 regmap_write(priv->map, TCSR0, 0);
166 regmap_write(priv->map, TCSR1, 0);
167 }
168
169 return 0;
170 }
171
xilinx_pwm_get_state(struct pwm_chip * chip,struct pwm_device * unused,struct pwm_state * state)172 static int xilinx_pwm_get_state(struct pwm_chip *chip,
173 struct pwm_device *unused,
174 struct pwm_state *state)
175 {
176 struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip);
177 u32 tlr0, tlr1, tcsr0, tcsr1;
178
179 regmap_read(priv->map, TLR0, &tlr0);
180 regmap_read(priv->map, TLR1, &tlr1);
181 regmap_read(priv->map, TCSR0, &tcsr0);
182 regmap_read(priv->map, TCSR1, &tcsr1);
183 state->period = xilinx_timer_get_period(priv, tlr0, tcsr0);
184 state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1);
185 state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1);
186 state->polarity = PWM_POLARITY_NORMAL;
187
188 /*
189 * 100% duty cycle results in constant low output. This may be (very)
190 * wrong if rate > 1 GHz, so fix this if you have such hardware :)
191 */
192 if (state->period == state->duty_cycle)
193 state->duty_cycle = 0;
194
195 return 0;
196 }
197
198 static const struct pwm_ops xilinx_pwm_ops = {
199 .apply = xilinx_pwm_apply,
200 .get_state = xilinx_pwm_get_state,
201 .owner = THIS_MODULE,
202 };
203
204 static const struct regmap_config xilinx_pwm_regmap_config = {
205 .reg_bits = 32,
206 .reg_stride = 4,
207 .val_bits = 32,
208 .val_format_endian = REGMAP_ENDIAN_LITTLE,
209 .max_register = TCR1,
210 };
211
xilinx_pwm_probe(struct platform_device * pdev)212 static int xilinx_pwm_probe(struct platform_device *pdev)
213 {
214 int ret;
215 struct device *dev = &pdev->dev;
216 struct device_node *np = dev->of_node;
217 struct xilinx_timer_priv *priv;
218 struct xilinx_pwm_device *xilinx_pwm;
219 u32 pwm_cells, one_timer, width;
220 void __iomem *regs;
221
222 /* If there are no PWM cells, this binding is for a timer */
223 ret = of_property_read_u32(np, "#pwm-cells", &pwm_cells);
224 if (ret == -EINVAL)
225 return -ENODEV;
226 if (ret)
227 return dev_err_probe(dev, ret, "could not read #pwm-cells\n");
228
229 xilinx_pwm = devm_kzalloc(dev, sizeof(*xilinx_pwm), GFP_KERNEL);
230 if (!xilinx_pwm)
231 return -ENOMEM;
232 platform_set_drvdata(pdev, xilinx_pwm);
233 priv = &xilinx_pwm->priv;
234
235 regs = devm_platform_ioremap_resource(pdev, 0);
236 if (IS_ERR(regs))
237 return PTR_ERR(regs);
238
239 priv->map = devm_regmap_init_mmio(dev, regs,
240 &xilinx_pwm_regmap_config);
241 if (IS_ERR(priv->map))
242 return dev_err_probe(dev, PTR_ERR(priv->map),
243 "Could not create regmap\n");
244
245 ret = of_property_read_u32(np, "xlnx,one-timer-only", &one_timer);
246 if (ret)
247 return dev_err_probe(dev, ret,
248 "Could not read xlnx,one-timer-only\n");
249
250 if (one_timer)
251 return dev_err_probe(dev, -EINVAL,
252 "Two timers required for PWM mode\n");
253
254 ret = of_property_read_u32(np, "xlnx,count-width", &width);
255 if (ret == -EINVAL)
256 width = 32;
257 else if (ret)
258 return dev_err_probe(dev, ret,
259 "Could not read xlnx,count-width\n");
260
261 if (width != 8 && width != 16 && width != 32)
262 return dev_err_probe(dev, -EINVAL,
263 "Invalid counter width %d\n", width);
264 priv->max = BIT_ULL(width) - 1;
265
266 /*
267 * The polarity of the Generate Out signals must be active high for PWM
268 * mode to work. We could determine this from the device tree, but
269 * alas, such properties are not allowed to be used.
270 */
271
272 priv->clk = devm_clk_get(dev, "s_axi_aclk");
273 if (IS_ERR(priv->clk))
274 return dev_err_probe(dev, PTR_ERR(priv->clk),
275 "Could not get clock\n");
276
277 ret = clk_prepare_enable(priv->clk);
278 if (ret)
279 return dev_err_probe(dev, ret, "Clock enable failed\n");
280 clk_rate_exclusive_get(priv->clk);
281
282 xilinx_pwm->chip.dev = dev;
283 xilinx_pwm->chip.ops = &xilinx_pwm_ops;
284 xilinx_pwm->chip.npwm = 1;
285 ret = pwmchip_add(&xilinx_pwm->chip);
286 if (ret) {
287 clk_rate_exclusive_put(priv->clk);
288 clk_disable_unprepare(priv->clk);
289 return dev_err_probe(dev, ret, "Could not register PWM chip\n");
290 }
291
292 return 0;
293 }
294
xilinx_pwm_remove(struct platform_device * pdev)295 static void xilinx_pwm_remove(struct platform_device *pdev)
296 {
297 struct xilinx_pwm_device *xilinx_pwm = platform_get_drvdata(pdev);
298
299 pwmchip_remove(&xilinx_pwm->chip);
300 clk_rate_exclusive_put(xilinx_pwm->priv.clk);
301 clk_disable_unprepare(xilinx_pwm->priv.clk);
302 }
303
304 static const struct of_device_id xilinx_pwm_of_match[] = {
305 { .compatible = "xlnx,xps-timer-1.00.a", },
306 {},
307 };
308 MODULE_DEVICE_TABLE(of, xilinx_pwm_of_match);
309
310 static struct platform_driver xilinx_pwm_driver = {
311 .probe = xilinx_pwm_probe,
312 .remove_new = xilinx_pwm_remove,
313 .driver = {
314 .name = "xilinx-pwm",
315 .of_match_table = of_match_ptr(xilinx_pwm_of_match),
316 },
317 };
318 module_platform_driver(xilinx_pwm_driver);
319
320 MODULE_ALIAS("platform:xilinx-pwm");
321 MODULE_DESCRIPTION("PWM driver for Xilinx LogiCORE IP AXI Timer");
322 MODULE_LICENSE("GPL");
323