Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754542AbbFOVRy (ORCPT ); Mon, 15 Jun 2015 17:17:54 -0400 Received: from mail-gw1-out.broadcom.com ([216.31.210.62]:41713 "EHLO mail-gw1-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751895AbbFOVRe (ORCPT ); Mon, 15 Jun 2015 17:17:34 -0400 X-IronPort-AV: E=Sophos;i="5.13,621,1427785200"; d="scan'208";a="67627102" From: Jonathan Richardson To: Tim Kryger , Dmitry Torokhov , Anatol Pomazau , Arun Ramamurthy , Thierry Reding CC: Scott Branden , Jonathan Richardson , bcm-kernel-feedback-list , , Subject: [PATCH v9 1/2] pwm: kona: Modify settings application sequence Date: Mon, 15 Jun 2015 14:21:01 -0700 Message-ID: <1434403262-24198-2-git-send-email-jonathar@broadcom.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1434403262-24198-1-git-send-email-jonathar@broadcom.com> References: <1434403262-24198-1-git-send-email-jonathar@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4412 Lines: 125 Update the driver so that settings are applied in accordance with the most recent version of the hardware spec. The revised sequence clears the trigger bit, waits 400ns, writes settings, sets the trigger bit, and waits another 400ns. This corrects an issue where occasionally a requested change was not properly reflected in the PWM output. Reviewed-by: Arun Ramamurthy Reviewed-by: Scott Branden Tested-by: Scott Branden Reviewed-by: Tim Kryger Signed-off-by: Jonathan Richardson --- drivers/pwm/pwm-bcm-kona.c | 47 +++++++++++++++++++++++++++++++++++--------- 1 file changed, 38 insertions(+), 9 deletions(-) diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c index 7af8fea..9b1d397 100644 --- a/drivers/pwm/pwm-bcm-kona.c +++ b/drivers/pwm/pwm-bcm-kona.c @@ -76,19 +76,36 @@ static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *_chip) return container_of(_chip, struct kona_pwmc, chip); } -static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan) +/* + * Clear trigger bit but set smooth bit to maintain old output. + */ +static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp, + unsigned int chan) { unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); - /* Clear trigger bit but set smooth bit to maintain old output */ value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan); value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan)); writel(value, kp->base + PWM_CONTROL_OFFSET); + /* + * There must be a min 400ns delay between clearing trigger and setting + * it. Failing to do this may result in no PWM signal. + */ + ndelay(400); +} + +static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan) +{ + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); + /* Set trigger bit and clear smooth bit to apply new settings */ value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan)); value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan); writel(value, kp->base + PWM_CONTROL_OFFSET); + + /* Trigger bit must be held high for at least 400 ns. */ + ndelay(400); } static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm, @@ -133,8 +150,14 @@ static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm, return -EINVAL; } - /* If the PWM channel is enabled, write the settings to the HW */ + /* + * Don't apply settings if disabled. The period and duty cycle are + * always calculated above to ensure the new values are + * validated immediately instead of on enable. + */ if (test_bit(PWMF_ENABLED, &pwm->flags)) { + kona_pwmc_prepare_for_settings(kp, chan); + value = readl(kp->base + PRESCALE_OFFSET); value &= ~PRESCALE_MASK(chan); value |= prescale << PRESCALE_SHIFT(chan); @@ -164,6 +187,8 @@ static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm, return ret; } + kona_pwmc_prepare_for_settings(kp, chan); + value = readl(kp->base + PWM_CONTROL_OFFSET); if (polarity == PWM_POLARITY_NORMAL) @@ -175,9 +200,6 @@ static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm, kona_pwmc_apply_settings(kp, chan); - /* Wait for waveform to settle before gating off the clock */ - ndelay(400); - clk_disable_unprepare(kp->clk); return 0; @@ -207,13 +229,20 @@ static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm) { struct kona_pwmc *kp = to_kona_pwmc(chip); unsigned int chan = pwm->hwpwm; + unsigned int value; + + kona_pwmc_prepare_for_settings(kp, chan); /* Simulate a disable by configuring for zero duty */ writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan)); - kona_pwmc_apply_settings(kp, chan); + writel(0, kp->base + PERIOD_COUNT_OFFSET(chan)); - /* Wait for waveform to settle before gating off the clock */ - ndelay(400); + /* Set prescale to 0 for this channel */ + value = readl(kp->base + PRESCALE_OFFSET); + value &= ~PRESCALE_MASK(chan); + writel(value, kp->base + PRESCALE_OFFSET); + + kona_pwmc_apply_settings(kp, chan); clk_disable_unprepare(kp->clk); } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/