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authorMichal Vokáč <michal.vokac@ysoft.com>2018-10-01 14:19:48 (GMT)
committerThierry Reding <thierry.reding@gmail.com>2018-12-12 10:52:47 (GMT)
commitbf9b0b1b0b6cd51797ce79b6fa5fc2d1baa2719e (patch)
treef8d92ab5fc082aea2e73d695902a2dc033c4478a /drivers/pwm
parent9f617ada9f823dff1944ebcf92ef4a05f5f322b7 (diff)
pwm: imx: Implement get_state() function for hardware readout
Implement the get_state() function and set the initial state to reflect real state of the hardware. This allows to keep the PWM running if it was enabled in bootloader. It is very similar to the GPIO behavior. GPIO pin set as output in bootloader keep the same setting in Linux unless it is reconfigured. If we find the PWM block enabled we need to prepare and enable its source clock otherwise the clock will be disabled late in the boot as unused. That will leave the PWM in enabled state but with disabled clock. That has a side effect that the PWM output is left at its current level at which the clock was disabled. It is totally non-deterministic and it may be LOW or HIGH. Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/pwm-imx.c53
1 files changed, 53 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
index 7a4907b..6cd3b72 100644
--- a/drivers/pwm/pwm-imx.c
+++ b/drivers/pwm/pwm-imx.c
@@ -83,6 +83,9 @@
#define MX3_PWM_SWR_LOOP 5
+/* PWMPR register value of 0xffff has the same effect as 0xfffe */
+#define MX3_PWMPR_MAX 0xfffe
+
struct imx_chip {
struct clk *clk_per;
@@ -93,6 +96,55 @@ struct imx_chip {
#define to_imx_chip(chip) container_of(chip, struct imx_chip, chip)
+static void imx_pwm_get_state(struct pwm_chip *chip,
+ struct pwm_device *pwm, struct pwm_state *state)
+{
+ struct imx_chip *imx = to_imx_chip(chip);
+ u32 period, prescaler, pwm_clk, ret, val;
+ u64 tmp;
+
+ val = readl(imx->mmio_base + MX3_PWMCR);
+
+ if (val & MX3_PWMCR_EN) {
+ state->enabled = true;
+ ret = clk_prepare_enable(imx->clk_per);
+ if (ret)
+ return;
+ } else {
+ state->enabled = false;
+ }
+
+ switch (FIELD_GET(MX3_PWMCR_POUTC, val)) {
+ case MX3_PWMCR_POUTC_NORMAL:
+ state->polarity = PWM_POLARITY_NORMAL;
+ break;
+ case MX3_PWMCR_POUTC_INVERTED:
+ state->polarity = PWM_POLARITY_INVERSED;
+ break;
+ default:
+ dev_warn(chip->dev, "can't set polarity, output disconnected");
+ }
+
+ prescaler = MX3_PWMCR_PRESCALER_GET(val);
+ pwm_clk = clk_get_rate(imx->clk_per);
+ pwm_clk = DIV_ROUND_CLOSEST_ULL(pwm_clk, prescaler);
+ val = readl(imx->mmio_base + MX3_PWMPR);
+ period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
+
+ /* PWMOUT (Hz) = PWMCLK / (PWMPR + 2) */
+ tmp = NSEC_PER_SEC * (u64)(period + 2);
+ state->period = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
+
+ /* PWMSAR can be read only if PWM is enabled */
+ if (state->enabled) {
+ val = readl(imx->mmio_base + MX3_PWMSAR);
+ tmp = NSEC_PER_SEC * (u64)(val);
+ state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
+ } else {
+ state->duty_cycle = 0;
+ }
+}
+
static int imx_pwm_config_v1(struct pwm_chip *chip,
struct pwm_device *pwm, int duty_ns, int period_ns)
{
@@ -272,6 +324,7 @@ static const struct pwm_ops imx_pwm_ops_v1 = {
static const struct pwm_ops imx_pwm_ops_v2 = {
.apply = imx_pwm_apply_v2,
+ .get_state = imx_pwm_get_state,
.owner = THIS_MODULE,
};

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