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Message-Id: <20170530193209.19247-3-alexandre.belloni@free-electrons.com>
Date: Tue, 30 May 2017 21:32:08 +0200
From: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To: Thierry Reding <thierry.reding@...il.com>,
Olliver Schinagl <o.schinagl@...imaker.com>
Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>,
Chen-Yu Tsai <wens@...e.org>,
Boris Brezillon <boris.brezillon@...e-electrons.com>,
Jonathan Liu <net147@...il.com>, linux-pwm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: [PATCH v2 2/3] pwm: sun4i: switch to atomic PWM
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).
Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
---
drivers/pwm/pwm-sun4i.c | 166 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 166 insertions(+)
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 175a69245a8a..cd8737d0804f 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -8,8 +8,10 @@
#include <linux/bitops.h>
#include <linux/clk.h>
+#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
+#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
@@ -81,6 +83,8 @@ struct sun4i_pwm_chip {
void __iomem *base;
spinlock_t ctrl_lock;
const struct sun4i_pwm_data *data;
+ unsigned long next_period[2];
+ bool needs_delay[2];
};
static inline struct sun4i_pwm_chip *to_sun4i_pwm_chip(struct pwm_chip *chip)
@@ -140,6 +144,167 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,
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 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 * state->period + NSEC_PER_SEC / 2;
+ do_div(div, NSEC_PER_SEC);
+ if (div - 1 > PWM_PRD_MASK)
+ prescaler = 0;
+ }
+
+ if (prescaler == 0) {
+ /* Go up from the first divider */
+ for (prescaler = 0; prescaler < PWM_PRESCAL_MASK; prescaler++) {
+ if (!prescaler_table[prescaler])
+ continue;
+ pval = prescaler_table[prescaler];
+ div = clk_rate;
+ 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)
+ return -EINVAL;
+ }
+
+ *prd = div;
+ div *= state->duty_cycle;
+ do_div(div, state->period);
+ *dty = div;
+ *prsclr = prescaler;
+
+ div = (u64)pval * NSEC_PER_SEC * *prd;
+ state->period = DIV_ROUND_CLOSEST_ULL(div, clk_rate);
+
+ div = (u64)pval * NSEC_PER_SEC * *dty;
+ state->duty_cycle = DIV_ROUND_CLOSEST_ULL(div, clk_rate);
+
+ return 0;
+}
+
+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);
+ struct pwm_state cstate;
+ u32 ctrl;
+ int ret;
+ unsigned int delay_us;
+ unsigned long now;
+
+ 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);
+ ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
+
+ if ((cstate.period != state->period) ||
+ (cstate.duty_cycle != state->duty_cycle)) {
+ u32 period, duty, val;
+ unsigned int prescaler;
+
+ 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;
+ }
+
+ if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
+ /* 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);
+
+ ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
+ ctrl |= BIT_CH(prescaler, pwm->hwpwm);
+ }
+
+ val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
+ sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
+ sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
+ usecs_to_jiffies(cstate.period / 1000 + 1);
+ sun4i_pwm->needs_delay[pwm->hwpwm] = true;
+ }
+
+ 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 (!sun4i_pwm->needs_delay[pwm->hwpwm]) {
+ ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
+ ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+ }
+
+ sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
+
+ spin_unlock(&sun4i_pwm->ctrl_lock);
+
+ if (state->enabled)
+ return 0;
+
+ if (!sun4i_pwm->needs_delay[pwm->hwpwm]) {
+ clk_disable_unprepare(sun4i_pwm->clk);
+ return 0;
+ }
+
+ /* We need a full period to elapse before disabling the channel. */
+ now = jiffies;
+ if (sun4i_pwm->needs_delay[pwm->hwpwm] &&
+ time_before(now, sun4i_pwm->next_period[pwm->hwpwm])) {
+ delay_us = jiffies_to_usecs(sun4i_pwm->next_period[pwm->hwpwm] -
+ now);
+ if ((delay_us / 500) > MAX_UDELAY_MS)
+ msleep(delay_us / 1000 + 1);
+ else
+ usleep_range(delay_us, delay_us * 2);
+ }
+ sun4i_pwm->needs_delay[pwm->hwpwm] = false;
+
+ spin_lock(&sun4i_pwm->ctrl_lock);
+ ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
+ ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+ ctrl &= ~BIT_CH(PWM_EN, 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 int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
@@ -301,6 +466,7 @@ static const struct pwm_ops sun4i_pwm_ops = {
.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,
};
--
2.11.0
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