[PATCH] pwm: sun4i: switch to atomic PWM
Alexandre Belloni
alexandre.belloni at free-electrons.com
Thu Apr 27 18:00:02 EDT 2017
Switch the driver to atomic PWM. This makes it easier to wait a proper
amount of time when changing the duty cycle before disabling the channel
(main use case is switching the duty cycle to 0 before disabling).
Also, the hardware read out is now greatly improved as it was formerly only
handling PWM polarity.
Signed-off-by: Alexandre Belloni <alexandre.belloni at free-electrons.com>
---
drivers/pwm/pwm-sun4i.c | 272 ++++++++++++++++++++++++++----------------------
1 file changed, 150 insertions(+), 122 deletions(-)
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index b0803f6c64d9..de300779c811 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -10,6 +10,7 @@
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
@@ -27,7 +28,6 @@
#define PWMCH_OFFSET 15
#define PWM_PRESCAL_MASK GENMASK(3, 0)
-#define PWM_PRESCAL_OFF 0
#define PWM_EN BIT(4)
#define PWM_ACT_STATE BIT(5)
#define PWM_CLK_GATING BIT(6)
@@ -44,6 +44,11 @@
#define PWM_DTY_MASK GENMASK(15, 0)
+#define PWM_MAX_PRD_US 198000000
+#define PWM_REG_PRD(reg) (((reg >> 16) & PWM_PRD_MASK) + 1)
+#define PWM_REG_DTY(reg) (reg & PWM_DTY_MASK)
+#define PWM_REG_PRESCAL(reg, chan) ((reg >> ((chan) * PWMCH_OFFSET)) & PWM_PRESCAL_MASK)
+
#define BIT_CH(bit, chan) ((bit) << ((chan) * PWMCH_OFFSET))
static const u32 prescaler_table[] = {
@@ -96,26 +101,65 @@ static inline void sun4i_pwm_writel(struct sun4i_pwm_chip *chip,
writel(val, chip->base + offset);
}
-static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
- int duty_ns, int period_ns)
+static void sun4i_pwm_get_state(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ struct pwm_state *state)
{
struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
- u32 prd, dty, val, clk_gate;
+ u64 clk_rate, tmp;
+ u32 val;
+ unsigned int prescaler;
+
+ clk_rate = clk_get_rate(sun4i_pwm->clk);
+
+ val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
+
+ if ((val == PWM_PRESCAL_MASK) && sun4i_pwm->data->has_prescaler_bypass)
+ prescaler = 1;
+ else
+ prescaler = prescaler_table[PWM_REG_PRESCAL(val, pwm->hwpwm)];
+
+ if (prescaler == 0)
+ return;
+
+ if (val & BIT_CH(PWM_ACT_STATE, pwm->hwpwm))
+ state->polarity = PWM_POLARITY_NORMAL;
+ else
+ state->polarity = PWM_POLARITY_INVERSED;
+
+ if (val & BIT_CH(PWM_CLK_GATING | PWM_EN, pwm->hwpwm))
+ state->enabled = true;
+ else
+ state->enabled = false;
+
+ val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm));
+
+ tmp = prescaler * NSEC_PER_SEC * PWM_REG_DTY(val);
+ state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
+
+ tmp = prescaler * NSEC_PER_SEC * PWM_REG_PRD(val);
+ state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
+}
+
+static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
+ struct pwm_state *state,
+ u32 *dty, u32 *prd, unsigned int *prsclr)
+{
u64 clk_rate, div = 0;
- unsigned int prescaler = 0;
- int err;
+ unsigned int pval, prescaler = 0;
clk_rate = clk_get_rate(sun4i_pwm->clk);
if (sun4i_pwm->data->has_prescaler_bypass) {
/* First, test without any prescaler when available */
prescaler = PWM_PRESCAL_MASK;
+ pval = 1;
/*
* When not using any prescaler, the clock period in nanoseconds
* is not an integer so round it half up instead of
* truncating to get less surprising values.
*/
- div = clk_rate * period_ns + NSEC_PER_SEC / 2;
+ div = clk_rate * state->period + NSEC_PER_SEC / 2;
do_div(div, NSEC_PER_SEC);
if (div - 1 > PWM_PRD_MASK)
prescaler = 0;
@@ -126,137 +170,139 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
for (prescaler = 0; prescaler < PWM_PRESCAL_MASK; prescaler++) {
if (!prescaler_table[prescaler])
continue;
+ pval = prescaler_table[prescaler];
div = clk_rate;
- do_div(div, prescaler_table[prescaler]);
- div = div * period_ns;
+ do_div(div, pval);
+ div = div * state->period;
do_div(div, NSEC_PER_SEC);
if (div - 1 <= PWM_PRD_MASK)
break;
}
- if (div - 1 > PWM_PRD_MASK) {
- dev_err(chip->dev, "period exceeds the maximum value\n");
+ if (div - 1 > PWM_PRD_MASK)
return -EINVAL;
- }
- }
-
- prd = div;
- div *= duty_ns;
- do_div(div, period_ns);
- dty = div;
-
- err = clk_prepare_enable(sun4i_pwm->clk);
- if (err) {
- dev_err(chip->dev, "failed to enable PWM clock\n");
- return err;
- }
-
- spin_lock(&sun4i_pwm->ctrl_lock);
- val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
-
- if (sun4i_pwm->data->has_rdy && (val & PWM_RDY(pwm->hwpwm))) {
- spin_unlock(&sun4i_pwm->ctrl_lock);
- clk_disable_unprepare(sun4i_pwm->clk);
- return -EBUSY;
- }
-
- clk_gate = val & BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
- if (clk_gate) {
- val &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
}
- val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
- val &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
- val |= BIT_CH(prescaler, pwm->hwpwm);
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
-
- val = (dty & PWM_DTY_MASK) | PWM_PRD(prd);
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
+ *prd = div;
+ div *= state->duty_cycle;
+ do_div(div, state->period);
+ *dty = div;
+ *prsclr = prescaler;
- if (clk_gate) {
- val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
- val |= clk_gate;
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
- }
+ div = (u64)pval * NSEC_PER_SEC * *prd;
+ state->period = DIV_ROUND_CLOSEST_ULL(div, clk_rate);
- spin_unlock(&sun4i_pwm->ctrl_lock);
- clk_disable_unprepare(sun4i_pwm->clk);
+ div = (u64)pval * NSEC_PER_SEC * *dty;
+ state->duty_cycle = DIV_ROUND_CLOSEST_ULL(div, clk_rate);
return 0;
}
-static int sun4i_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
- enum pwm_polarity polarity)
+static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
{
struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
- u32 val;
- int ret;
-
- ret = clk_prepare_enable(sun4i_pwm->clk);
- if (ret) {
- dev_err(chip->dev, "failed to enable PWM clock\n");
- return ret;
+ struct pwm_state cstate;
+ u32 ctrl;
+ int delay_us, ret;
+ bool needs_delay = false, prescaler_changed = false;
+
+ pwm_get_state(pwm, &cstate);
+
+ if (!cstate.enabled) {
+ ret = clk_prepare_enable(sun4i_pwm->clk);
+ if (ret) {
+ dev_err(chip->dev, "failed to enable PWM clock\n");
+ return ret;
+ }
}
spin_lock(&sun4i_pwm->ctrl_lock);
- val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
+ ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
- if (polarity != PWM_POLARITY_NORMAL)
- val &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
- else
- val |= BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
+ if ((cstate.period != state->period) ||
+ (cstate.duty_cycle != state->duty_cycle)) {
+ u32 period, duty, val;
+ unsigned int prescaler;
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
+ needs_delay = true;
- spin_unlock(&sun4i_pwm->ctrl_lock);
- clk_disable_unprepare(sun4i_pwm->clk);
+ ret = sun4i_pwm_calculate(sun4i_pwm, state,
+ &duty, &period, &prescaler);
+ if (ret) {
+ dev_err(chip->dev, "period exceeds the maximum value\n");
+ spin_unlock(&sun4i_pwm->ctrl_lock);
+ if (!cstate.enabled)
+ clk_disable_unprepare(sun4i_pwm->clk);
+ return ret;
+ }
- return 0;
-}
+ if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
+ prescaler_changed = true;
+ /* Prescaler changed, the clock has to be gated */
+ ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+ sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
-static int sun4i_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
- struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
- u32 val;
- int ret;
+ ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
+ ctrl |= BIT_CH(prescaler, pwm->hwpwm);
+ }
- ret = clk_prepare_enable(sun4i_pwm->clk);
- if (ret) {
- dev_err(chip->dev, "failed to enable PWM clock\n");
- return ret;
+ val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
+ sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
}
- spin_lock(&sun4i_pwm->ctrl_lock);
- val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
- val |= BIT_CH(PWM_EN, pwm->hwpwm);
- val |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
- spin_unlock(&sun4i_pwm->ctrl_lock);
-
- return 0;
-}
+ if (state->polarity != PWM_POLARITY_NORMAL)
+ ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
+ else
+ ctrl |= BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
+
+ ctrl |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+ if (state->enabled) {
+ ctrl |= BIT_CH(PWM_EN, pwm->hwpwm);
+ } else if (!needs_delay) {
+ ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
+ ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+ }
-static void sun4i_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
- struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
- u32 val;
+ sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
- spin_lock(&sun4i_pwm->ctrl_lock);
- val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
- val &= ~BIT_CH(PWM_EN, pwm->hwpwm);
- val &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
- sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
spin_unlock(&sun4i_pwm->ctrl_lock);
- clk_disable_unprepare(sun4i_pwm->clk);
+ if (!needs_delay)
+ return 0;
+
+ /* We need a full (previous) period to elapse before disabling the
+ * channel. If a ready bit is available, wait for it instead of waiting
+ * for a full period.
+ *
+ * If the new period is greater than the previous one, the prescaler may
+ * have changed and the previous period may go slower.
+ *
+ */
+ delay_us = max(state->period / 1000 + 1, cstate.period / 1000 + 1);
+ if ((cstate.enabled && !state->enabled) || !sun4i_pwm->data->has_rdy)
+ usleep_range(delay_us, delay_us * 2);
+ else
+ readl_poll_timeout(sun4i_pwm->base + PWM_CTRL_REG, ctrl,
+ !(ctrl & PWM_RDY(pwm->hwpwm)),
+ delay_us / 4, PWM_MAX_PRD_US);
+
+ if (!state->enabled) {
+ spin_lock(&sun4i_pwm->ctrl_lock);
+ ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
+ ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+ sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
+ spin_unlock(&sun4i_pwm->ctrl_lock);
+
+ clk_disable_unprepare(sun4i_pwm->clk);
+ }
+
+ return 0;
}
static const struct pwm_ops sun4i_pwm_ops = {
- .config = sun4i_pwm_config,
- .set_polarity = sun4i_pwm_set_polarity,
- .enable = sun4i_pwm_enable,
- .disable = sun4i_pwm_disable,
+ .apply = sun4i_pwm_apply,
+ .get_state = sun4i_pwm_get_state,
.owner = THIS_MODULE,
};
@@ -316,8 +362,7 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
{
struct sun4i_pwm_chip *pwm;
struct resource *res;
- u32 val;
- int i, ret;
+ int ret;
const struct of_device_id *match;
match = of_match_device(sun4i_pwm_dt_ids, &pdev->dev);
@@ -354,24 +399,7 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, pwm);
- ret = clk_prepare_enable(pwm->clk);
- if (ret) {
- dev_err(&pdev->dev, "failed to enable PWM clock\n");
- goto clk_error;
- }
-
- val = sun4i_pwm_readl(pwm, PWM_CTRL_REG);
- for (i = 0; i < pwm->chip.npwm; i++)
- if (!(val & BIT_CH(PWM_ACT_STATE, i)))
- pwm_set_polarity(&pwm->chip.pwms[i],
- PWM_POLARITY_INVERSED);
- clk_disable_unprepare(pwm->clk);
-
return 0;
-
-clk_error:
- pwmchip_remove(&pwm->chip);
- return ret;
}
static int sun4i_pwm_remove(struct platform_device *pdev)
--
2.11.0
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