linux-kernel - [RFC v4 10/10] pwm: dwc: add PWM bit unset in get

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Message-Id: <20220816211454.237751-11-ben.dooks@sifive.com>
Date:   Tue, 16 Aug 2022 22:14:54 +0100
From:   Ben Dooks <ben.dooks@...ive.com>
To:     linux-pwm@...r.kernel.org
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lee Jones <lee.jones@...aro.org>,
        u.kleine-koenig@...gutronix.de,
        Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        jarkko.nikula@...ux.intel.com,
        William Salmon <william.salmon@...ive.com>,
        Jude Onyenegecha <jude.onyenegecha@...ive.com>,
        Ben Dooks <ben.dooks@...ive.com>
Subject: [RFC v4 10/10] pwm: dwc: add PWM bit unset in get_state call

If we are not in PWM mode, then the output is technically a 50%
output based on a single timer instead of the high-low based on
the two counters. Add a check for the PWM mode in dwc_pwm_get_state()
and if DWC_TIM_CTRL_PWM is not set, then return a 50% cycle.

This may only be an issue on initialisation, as the rest of the
code currently assumes we're always going to have the extended
PWM mode using two counters.

Signed-off-by: Ben Dooks <ben.dooks@...ive.com>
---
v4:
 - fixed review comment on mulit-line calculations
---
 drivers/pwm/pwm-dwc.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/drivers/pwm/pwm-dwc.c b/drivers/pwm/pwm-dwc.c
index 1251620ab771..5ef0fe7ea3e9 100644
--- a/drivers/pwm/pwm-dwc.c
+++ b/drivers/pwm/pwm-dwc.c
@@ -121,23 +121,30 @@ static void dwc_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 {
 	struct dwc_pwm *dwc = to_dwc_pwm(chip);
 	u64 duty, period;
+	u32 ctrl, ld, ld2;
 
 	pm_runtime_get_sync(chip->dev);
 
-	state->enabled = !!(dwc_pwm_readl(dwc,
-				DWC_TIM_CTRL(pwm->hwpwm)) & DWC_TIM_CTRL_EN);
+	ctrl = dwc_pwm_readl(dwc, DWC_TIM_CTRL(pwm->hwpwm));
+	ld = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(pwm->hwpwm));
+	ld2 = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(pwm->hwpwm));
 
-	duty = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(pwm->hwpwm));
-	duty += 1;
-	duty *= dwc->clk_ns;
-	state->duty_cycle = duty;
+	state->enabled = !!(ctrl & DWC_TIM_CTRL_EN);
 
-	period = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(pwm->hwpwm));
-	period += 1;
-	period *= dwc->clk_ns;
-	period += duty;
-	state->period = period;
+	/* If we're not in PWM, technically the output is a 50-50
+	 * based on the timer load-count only.
+	 */
+	if (ctrl & DWC_TIM_CTRL_PWM) {
+		duty = (ld + 1) * dwc->clk_ns;
+		period = (ld2 + 1)  * dwc->clk_ns;
+		period += duty;
+	} else {
+		duty = (ld + 1) * dwc->clk_ns;
+		period = duty * 2;
+	}
 
+	state->period = period;
+	state->duty_cycle = duty;
 	state->polarity = PWM_POLARITY_INVERSED;
 
 	pm_runtime_put_sync(chip->dev);
-- 
2.35.1