linux-kernel - [PATCH v6] staging: greybus: introduce pwm

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Message-Id: <1647597432-27586-1-git-send-email-chensong_2000@189.cn>
Date:   Fri, 18 Mar 2022 17:57:12 +0800
From:   Song Chen <chensong_2000@....cn>
To:     johan@...nel.org, elder@...nel.org, gregkh@...uxfoundation.org,
        thierry.reding@...il.com, u.kleine-koenig@...gutronix.de,
        lee.jones@...aro.org, greybus-dev@...ts.linaro.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-pwm@...r.kernel.org, elder@...e.org, elder@...aro.org
Cc:     Song Chen <chensong_2000@....cn>
Subject: [PATCH v6] staging: greybus: introduce pwm_ops::apply

Introduce newer .apply function in pwm_ops to replace legacy operations
including enable, disable, config and set_polarity.

This guarantees atomic changes of the pwm controller configuration.

Signed-off-by: Song Chen <chensong_2000@....cn>

---
v2:
1, define duty_cycle and period as u64 in gb_pwm_config_operation.
2, define duty and period as u64 in gb_pwm_config_request.
3, disable before configuring duty and period if the eventual goal
   is a disabled state.

v3:
Regarding duty_cycle and period, I read more discussion in this thread,
min, warn or -EINVAL, seems no perfect way acceptable for everyone.
How about we limit their value to INT_MAX and throw a warning at the
same time when they are wrong?

v4:
1, explain why legacy operations are replaced.
2, cap the value of period and duty to U32_MAX.

v5:
1, revise commit message.

v6:
1, revise commit message.
2, explain why capping the value of period and duty to U32_MAX in
   comment.
---
 drivers/staging/greybus/pwm.c | 64 ++++++++++++++++++++++-------------
 1 file changed, 40 insertions(+), 24 deletions(-)

diff --git a/drivers/staging/greybus/pwm.c b/drivers/staging/greybus/pwm.c
index 891a6a672378..ad20ec24031e 100644
--- a/drivers/staging/greybus/pwm.c
+++ b/drivers/staging/greybus/pwm.c
@@ -204,43 +204,59 @@ static void gb_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 	gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);
 }
 
-static int gb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			 int duty_ns, int period_ns)
+static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			const struct pwm_state *state)
 {
+	int err;
+	bool enabled = pwm->state.enabled;
+	u64 period = state->period;
+	u64 duty_cycle = state->duty_cycle;
 	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
 
-	return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, period_ns);
-};
+	/* Set polarity */
+	if (state->polarity != pwm->state.polarity) {
+		if (enabled) {
+			gb_pwm_disable_operation(pwmc, pwm->hwpwm);
+			enabled = false;
+		}
+		err = gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, state->polarity);
+		if (err)
+			return err;
+	}
 
-static int gb_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
-			       enum pwm_polarity polarity)
-{
-	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
+	if (!state->enabled) {
+		if (enabled)
+			gb_pwm_disable_operation(pwmc, pwm->hwpwm);
+		return 0;
+	}
 
-	return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
-};
+	/*
+	 * Set period and duty cycle
+	 *
+	 * PWM privodes 64-bit period and duty_cycle, but greybus only accepts
+	 * 32-bit, so their values have to be limited to U32_MAX.
+	 */
+	if (period > U32_MAX)
+		period = U32_MAX;
 
-static int gb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
+	if (duty_cycle > period)
+		duty_cycle = period;
 
-	return gb_pwm_enable_operation(pwmc, pwm->hwpwm);
-};
+	err = gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_cycle, period);
+	if (err)
+		return err;
 
-static void gb_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
+	/* enable/disable */
+	if (!enabled)
+		return gb_pwm_enable_operation(pwmc, pwm->hwpwm);
 
-	gb_pwm_disable_operation(pwmc, pwm->hwpwm);
-};
+	return 0;
+}
 
 static const struct pwm_ops gb_pwm_ops = {
 	.request = gb_pwm_request,
 	.free = gb_pwm_free,
-	.config = gb_pwm_config,
-	.set_polarity = gb_pwm_set_polarity,
-	.enable = gb_pwm_enable,
-	.disable = gb_pwm_disable,
+	.apply = gb_pwm_apply,
 	.owner = THIS_MODULE,
 };
 
-- 
2.25.1