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authorFabrice Gasnier <fabrice.gasnier@st.com>2017-08-28 12:04:09 +0200
committerLee Jones <lee.jones@linaro.org>2017-09-04 14:49:09 +0100
commite70a540b4e023045a85529edbd04da73a0c72a12 (patch)
treeb8da2feda9c833bbf41e5e18ae12d57bf107687c /drivers/pwm/pwm-stm32-lp.c
parente8924005b4e7964313536547d4b73406330be26d (diff)
pwm: Add STM32 LPTimer PWM driver
Add support for single PWM channel on Low-Power Timer, that can be found on some STM32 platforms. Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com> Acked-by: Thierry Reding <thierry.reding@gmail.com> Signed-off-by: Lee Jones <lee.jones@linaro.org>
Diffstat (limited to 'drivers/pwm/pwm-stm32-lp.c')
-rw-r--r--drivers/pwm/pwm-stm32-lp.c246
1 files changed, 246 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c
new file mode 100644
index 000000000000..9793b296108f
--- /dev/null
+++ b/drivers/pwm/pwm-stm32-lp.c
@@ -0,0 +1,246 @@
+/*
+ * STM32 Low-Power Timer PWM driver
+ *
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Gerald Baeza <gerald.baeza@st.com>
+ *
+ * License terms: GNU General Public License (GPL), version 2
+ *
+ * Inspired by Gerald Baeza's pwm-stm32 driver
+ */
+
+#include <linux/bitfield.h>
+#include <linux/mfd/stm32-lptimer.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+struct stm32_pwm_lp {
+ struct pwm_chip chip;
+ struct clk *clk;
+ struct regmap *regmap;
+};
+
+static inline struct stm32_pwm_lp *to_stm32_pwm_lp(struct pwm_chip *chip)
+{
+ return container_of(chip, struct stm32_pwm_lp, chip);
+}
+
+/* STM32 Low-Power Timer is preceded by a configurable power-of-2 prescaler */
+#define STM32_LPTIM_MAX_PRESCALER 128
+
+static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip);
+ unsigned long long prd, div, dty;
+ struct pwm_state cstate;
+ u32 val, mask, cfgr, presc = 0;
+ bool reenable;
+ int ret;
+
+ pwm_get_state(pwm, &cstate);
+ reenable = !cstate.enabled;
+
+ if (!state->enabled) {
+ if (cstate.enabled) {
+ /* Disable LP timer */
+ ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
+ if (ret)
+ return ret;
+ /* disable clock to PWM counter */
+ clk_disable(priv->clk);
+ }
+ return 0;
+ }
+
+ /* Calculate the period and prescaler value */
+ div = (unsigned long long)clk_get_rate(priv->clk) * state->period;
+ do_div(div, NSEC_PER_SEC);
+ prd = div;
+ while (div > STM32_LPTIM_MAX_ARR) {
+ presc++;
+ if ((1 << presc) > STM32_LPTIM_MAX_PRESCALER) {
+ dev_err(priv->chip.dev, "max prescaler exceeded\n");
+ return -EINVAL;
+ }
+ div = prd >> presc;
+ }
+ prd = div;
+
+ /* Calculate the duty cycle */
+ dty = prd * state->duty_cycle;
+ do_div(dty, state->period);
+
+ if (!cstate.enabled) {
+ /* enable clock to drive PWM counter */
+ ret = clk_enable(priv->clk);
+ if (ret)
+ return ret;
+ }
+
+ ret = regmap_read(priv->regmap, STM32_LPTIM_CFGR, &cfgr);
+ if (ret)
+ goto err;
+
+ if ((FIELD_GET(STM32_LPTIM_PRESC, cfgr) != presc) ||
+ (FIELD_GET(STM32_LPTIM_WAVPOL, cfgr) != state->polarity)) {
+ val = FIELD_PREP(STM32_LPTIM_PRESC, presc);
+ val |= FIELD_PREP(STM32_LPTIM_WAVPOL, state->polarity);
+ mask = STM32_LPTIM_PRESC | STM32_LPTIM_WAVPOL;
+
+ /* Must disable LP timer to modify CFGR */
+ reenable = true;
+ ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
+ if (ret)
+ goto err;
+
+ ret = regmap_update_bits(priv->regmap, STM32_LPTIM_CFGR, mask,
+ val);
+ if (ret)
+ goto err;
+ }
+
+ if (reenable) {
+ /* Must (re)enable LP timer to modify CMP & ARR */
+ ret = regmap_write(priv->regmap, STM32_LPTIM_CR,
+ STM32_LPTIM_ENABLE);
+ if (ret)
+ goto err;
+ }
+
+ ret = regmap_write(priv->regmap, STM32_LPTIM_ARR, prd - 1);
+ if (ret)
+ goto err;
+
+ ret = regmap_write(priv->regmap, STM32_LPTIM_CMP, prd - (1 + dty));
+ if (ret)
+ goto err;
+
+ /* ensure CMP & ARR registers are properly written */
+ ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
+ (val & STM32_LPTIM_CMPOK_ARROK),
+ 100, 1000);
+ if (ret) {
+ dev_err(priv->chip.dev, "ARR/CMP registers write issue\n");
+ goto err;
+ }
+ ret = regmap_write(priv->regmap, STM32_LPTIM_ICR,
+ STM32_LPTIM_CMPOKCF_ARROKCF);
+ if (ret)
+ goto err;
+
+ if (reenable) {
+ /* Start LP timer in continuous mode */
+ ret = regmap_update_bits(priv->regmap, STM32_LPTIM_CR,
+ STM32_LPTIM_CNTSTRT,
+ STM32_LPTIM_CNTSTRT);
+ if (ret) {
+ regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
+ goto err;
+ }
+ }
+
+ return 0;
+err:
+ if (!cstate.enabled)
+ clk_disable(priv->clk);
+
+ return ret;
+}
+
+static void stm32_pwm_lp_get_state(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip);
+ unsigned long rate = clk_get_rate(priv->clk);
+ u32 val, presc, prd;
+ u64 tmp;
+
+ regmap_read(priv->regmap, STM32_LPTIM_CR, &val);
+ state->enabled = !!FIELD_GET(STM32_LPTIM_ENABLE, val);
+ /* Keep PWM counter clock refcount in sync with PWM initial state */
+ if (state->enabled)
+ clk_enable(priv->clk);
+
+ regmap_read(priv->regmap, STM32_LPTIM_CFGR, &val);
+ presc = FIELD_GET(STM32_LPTIM_PRESC, val);
+ state->polarity = FIELD_GET(STM32_LPTIM_WAVPOL, val);
+
+ regmap_read(priv->regmap, STM32_LPTIM_ARR, &prd);
+ tmp = prd + 1;
+ tmp = (tmp << presc) * NSEC_PER_SEC;
+ state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate);
+
+ regmap_read(priv->regmap, STM32_LPTIM_CMP, &val);
+ tmp = prd - val;
+ tmp = (tmp << presc) * NSEC_PER_SEC;
+ state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);
+}
+
+static const struct pwm_ops stm32_pwm_lp_ops = {
+ .owner = THIS_MODULE,
+ .apply = stm32_pwm_lp_apply,
+ .get_state = stm32_pwm_lp_get_state,
+};
+
+static int stm32_pwm_lp_probe(struct platform_device *pdev)
+{
+ struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent);
+ struct stm32_pwm_lp *priv;
+ int ret;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->regmap = ddata->regmap;
+ priv->clk = ddata->clk;
+ priv->chip.base = -1;
+ priv->chip.dev = &pdev->dev;
+ priv->chip.ops = &stm32_pwm_lp_ops;
+ priv->chip.npwm = 1;
+
+ ret = pwmchip_add(&priv->chip);
+ if (ret < 0)
+ return ret;
+
+ platform_set_drvdata(pdev, priv);
+
+ return 0;
+}
+
+static int stm32_pwm_lp_remove(struct platform_device *pdev)
+{
+ struct stm32_pwm_lp *priv = platform_get_drvdata(pdev);
+ unsigned int i;
+
+ for (i = 0; i < priv->chip.npwm; i++)
+ if (pwm_is_enabled(&priv->chip.pwms[i]))
+ pwm_disable(&priv->chip.pwms[i]);
+
+ return pwmchip_remove(&priv->chip);
+}
+
+static const struct of_device_id stm32_pwm_lp_of_match[] = {
+ { .compatible = "st,stm32-pwm-lp", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, stm32_pwm_lp_of_match);
+
+static struct platform_driver stm32_pwm_lp_driver = {
+ .probe = stm32_pwm_lp_probe,
+ .remove = stm32_pwm_lp_remove,
+ .driver = {
+ .name = "stm32-pwm-lp",
+ .of_match_table = of_match_ptr(stm32_pwm_lp_of_match),
+ },
+};
+module_platform_driver(stm32_pwm_lp_driver);
+
+MODULE_ALIAS("platform:stm32-pwm-lp");
+MODULE_DESCRIPTION("STMicroelectronics STM32 PWM LP driver");
+MODULE_LICENSE("GPL v2");

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