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authorJernej Skrabec <jernej.skrabec@siol.net>2019-11-24 18:29:07 +0100
committerThierry Reding <thierry.reding@gmail.com>2020-01-08 12:50:41 +0100
commit9f28e95b5286fce63a3d0d90dc7ca43eca8dda58 (patch)
tree8a00e0622d3f7d8cff63d76cf5e0f291288ca7f5 /drivers/pwm
parentfa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 (diff)
downloadlinux-9f28e95b5286fce63a3d0d90dc7ca43eca8dda58.tar.bz2
pwm: sun4i: Add support to output source clock directly
PWM core has an option to bypass whole logic and output unchanged source clock as PWM output. This is achieved by enabling bypass bit. Note that when bypass is enabled, no other setting has any meaning, not even enable bit. This mode of operation is needed to achieve high enough frequency to serve as clock source for AC200 chip which is integrated into same package as H6 SoC. Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net> Signed-off-by: Clément Péron <peron.clem@gmail.com> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/pwm-sun4i.c48
1 files changed, 46 insertions, 2 deletions
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index e369b5a398f4..63aa9da92c22 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -3,6 +3,10 @@
* Driver for Allwinner sun4i Pulse Width Modulation Controller
*
* Copyright (C) 2014 Alexandre Belloni <alexandre.belloni@free-electrons.com>
+ *
+ * Limitations:
+ * - When outputing the source clock directly, the PWM logic will be bypassed
+ * and the currently running period is not guaranteed to be completed
*/
#include <linux/bitops.h>
@@ -73,6 +77,7 @@ static const u32 prescaler_table[] = {
struct sun4i_pwm_data {
bool has_prescaler_bypass;
+ bool has_direct_mod_clk_output;
unsigned int npwm;
};
@@ -118,6 +123,20 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,
val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
+ /*
+ * PWM chapter in H6 manual has a diagram which explains that if bypass
+ * bit is set, no other setting has any meaning. Even more, experiment
+ * proved that also enable bit is ignored in this case.
+ */
+ if ((val & BIT_CH(PWM_BYPASS, pwm->hwpwm)) &&
+ sun4i_pwm->data->has_direct_mod_clk_output) {
+ state->period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate);
+ state->duty_cycle = DIV_ROUND_UP_ULL(state->period, 2);
+ state->polarity = PWM_POLARITY_NORMAL;
+ state->enabled = true;
+ return;
+ }
+
if ((PWM_REG_PRESCAL(val, pwm->hwpwm) == PWM_PRESCAL_MASK) &&
sun4i_pwm->data->has_prescaler_bypass)
prescaler = 1;
@@ -149,13 +168,24 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,
static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
const struct pwm_state *state,
- u32 *dty, u32 *prd, unsigned int *prsclr)
+ u32 *dty, u32 *prd, unsigned int *prsclr,
+ bool *bypass)
{
u64 clk_rate, div = 0;
unsigned int pval, prescaler = 0;
clk_rate = clk_get_rate(sun4i_pwm->clk);
+ *bypass = sun4i_pwm->data->has_direct_mod_clk_output &&
+ state->enabled &&
+ (state->period * clk_rate >= NSEC_PER_SEC) &&
+ (state->period * clk_rate < 2 * NSEC_PER_SEC) &&
+ (state->duty_cycle * clk_rate * 2 >= NSEC_PER_SEC);
+
+ /* Skip calculation of other parameters if we bypass them */
+ if (*bypass)
+ return 0;
+
if (sun4i_pwm->data->has_prescaler_bypass) {
/* First, test without any prescaler when available */
prescaler = PWM_PRESCAL_MASK;
@@ -206,6 +236,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
int ret;
unsigned int delay_us, prescaler;
unsigned long now;
+ bool bypass;
pwm_get_state(pwm, &cstate);
@@ -220,7 +251,8 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
spin_lock(&sun4i_pwm->ctrl_lock);
ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
- ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler);
+ ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
+ &bypass);
if (ret) {
dev_err(chip->dev, "period exceeds the maximum value\n");
spin_unlock(&sun4i_pwm->ctrl_lock);
@@ -229,6 +261,18 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
return ret;
}
+ if (sun4i_pwm->data->has_direct_mod_clk_output) {
+ if (bypass) {
+ ctrl |= BIT_CH(PWM_BYPASS, pwm->hwpwm);
+ /* We can skip other parameter */
+ sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
+ spin_unlock(&sun4i_pwm->ctrl_lock);
+ return 0;
+ }
+
+ ctrl &= ~BIT_CH(PWM_BYPASS, pwm->hwpwm);
+ }
+
if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
/* Prescaler changed, the clock has to be gated */
ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);