Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933157AbaLDU0f (ORCPT ); Thu, 4 Dec 2014 15:26:35 -0500 Received: from mail-gw2-out.broadcom.com ([216.31.210.63]:37995 "EHLO mail-gw2-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933130AbaLDU0c (ORCPT ); Thu, 4 Dec 2014 15:26:32 -0500 X-IronPort-AV: E=Sophos;i="5.07,517,1413270000"; d="scan'208";a="52307285" Message-ID: <5480C365.6020807@broadcom.com> Date: Thu, 4 Dec 2014 12:26:13 -0800 From: Jonathan Richardson User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Tim Kryger CC: Scott Branden , Thierry Reding , Ray Jui , Arun Ramamurthy , , , Linux Kernel Mailing List Subject: Re: [PATCH v2 3/4] pwm: kona: Fix enable, disable and config procedures References: <1416944441-12066-1-git-send-email-sbranden@broadcom.com> <1416944441-12066-4-git-send-email-sbranden@broadcom.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tim, Comments below. On 14-11-25 11:29 PM, Tim Kryger wrote: > On Tue, Nov 25, 2014 at 11:40 AM, Scott Branden wrote: >> From: Arun Ramamurthy >> >> - Added helper functions to set and clear smooth and trigger bits >> - Added 400ns delays when clearing and setting trigger bit as requied >> by spec >> - Added helper function to write prescale and other settings >> - Updated config procedure to match spec >> - Added code to handle pwn config when channel is disabled >> - Updated disable procedure to match spec >> >> Signed-off-by: Arun Ramamurthy >> Reviewed-by: Ray Jui >> Signed-off-by: Scott Branden >> --- >> drivers/pwm/pwm-bcm-kona.c | 100 +++++++++++++++++++++++++++++++++++---------- >> 1 file changed, 78 insertions(+), 22 deletions(-) > > The driver is fairly small and this change rewrites a considerable amount of it. > > Is there a actually specific deficiency that this change is intended to address? > > I'm not sure all the extra helper functions improve readability. > Hopefully my summary in the previous reply helps clarify. I'm going to remove all the helper functions to make the changes as simple as possible. >> >> diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c >> index fa0b5bf..06fa983 100644 >> --- a/drivers/pwm/pwm-bcm-kona.c >> +++ b/drivers/pwm/pwm-bcm-kona.c >> @@ -65,6 +65,10 @@ >> #define DUTY_CYCLE_HIGH_MIN (0x00000000) >> #define DUTY_CYCLE_HIGH_MAX (0x00ffffff) >> >> +/* The delay required after clearing or setting >> + PWMOUT_ENABLE*/ >> +#define PWMOUT_ENABLE_HOLD_DELAY 400 >> + >> struct kona_pwmc { >> struct pwm_chip chip; >> void __iomem *base; >> @@ -76,28 +80,70 @@ 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) >> +static inline void kona_pwmc_set_trigger(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); >> + /* set trigger bit to enable channel */ >> + value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan); >> + writel(value, kp->base + PWM_CONTROL_OFFSET); >> + ndelay(PWMOUT_ENABLE_HOLD_DELAY); >> +} >> +static inline void kona_pwmc_clear_trigger(struct kona_pwmc *kp, >> + unsigned int chan) >> +{ >> + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); >> + >> + /* Clear trigger bit */ >> value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan)); >> writel(value, kp->base + PWM_CONTROL_OFFSET); >> + ndelay(PWMOUT_ENABLE_HOLD_DELAY); >> +} >> >> - /* Set trigger bit and clear smooth bit to apply new settings */ >> +static inline void kona_pwmc_clear_smooth(struct kona_pwmc *kp, >> + unsigned int chan) >> +{ >> + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); >> + >> + /* Clear smooth bit */ >> value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan)); >> - value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan); >> writel(value, kp->base + PWM_CONTROL_OFFSET); >> } >> >> +static inline void kona_pwmc_set_smooth(struct kona_pwmc *kp, unsigned int chan) >> +{ >> + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET); >> + >> + /* set smooth bit to maintain old output */ >> + value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan); >> + writel(value, kp->base + PWM_CONTROL_OFFSET); >> +} >> + >> +static void kona_pwmc_write_settings(struct kona_pwmc *kp, unsigned int chan, >> + unsigned long prescale, unsigned long pc, >> + unsigned long dc) >> +{ >> + unsigned int value; >> + >> + value = readl(kp->base + PRESCALE_OFFSET); >> + value &= ~PRESCALE_MASK(chan); >> + value |= prescale << PRESCALE_SHIFT(chan); >> + writel(value, kp->base + PRESCALE_OFFSET); >> + >> + writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan)); >> + >> + writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan)); >> + >> +} >> + >> static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm, >> int duty_ns, int period_ns) >> { >> struct kona_pwmc *kp = to_kona_pwmc(chip); >> u64 val, div, rate; >> unsigned long prescale = PRESCALE_MIN, pc, dc; >> - unsigned int value, chan = pwm->hwpwm; >> + unsigned int ret, chan = pwm->hwpwm; >> >> /* >> * Find period count, duty count and prescale to suit duty_ns and >> @@ -133,19 +179,30 @@ 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 */ >> - if (test_bit(PWMF_ENABLED, &pwm->flags)) { >> - value = readl(kp->base + PRESCALE_OFFSET); >> - value &= ~PRESCALE_MASK(chan); >> - value |= prescale << PRESCALE_SHIFT(chan); >> - writel(value, kp->base + PRESCALE_OFFSET); >> >> - writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan)); >> + /* If the PWM channel is not enabled, enable the clock */ >> + if (!test_bit(PWMF_ENABLED, &pwm->flags)) { >> + ret = clk_prepare_enable(kp->clk); >> + if (ret < 0) { >> + dev_err(chip->dev, "failed to enable clock: %d\n", ret); >> + return ret; >> + } >> + } >> >> - writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan)); >> + /* Set smooth bit to maintain old output */ >> + kona_pwmc_set_smooth(kp, chan); >> + kona_pwmc_clear_trigger(kp, chan); >> + >> + /* apply new settings */ >> + kona_pwmc_write_settings(kp, chan, prescale, pc, dc); >> + >> + /*If the PWM is enabled, enable the channel with the new settings >> + and if not disable the clock*/ >> + if (test_bit(PWMF_ENABLED, &pwm->flags)) >> + kona_pwmc_set_trigger(kp, chan); >> + else >> + clk_disable_unprepare(kp->clk); >> >> - kona_pwmc_apply_settings(kp, chan); >> - } >> >> return 0; >> } >> @@ -188,7 +245,6 @@ static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm) >> dev_err(chip->dev, "failed to enable clock: %d\n", ret); >> return ret; >> } >> - >> ret = kona_pwmc_config(chip, pwm, pwm->duty_cycle, pwm->period); >> if (ret < 0) { >> clk_disable_unprepare(kp->clk); >> @@ -203,12 +259,12 @@ 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; >> >> + kona_pwmc_clear_smooth(kp, chan); >> + kona_pwmc_clear_trigger(kp, chan); > > I believe the output will spike high here. Likely not what you want... > >> /* Simulate a disable by configuring for zero duty */ >> - writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan)); >> - kona_pwmc_apply_settings(kp, chan); >> - >> - /* Wait for waveform to settle before gating off the clock */ >> - ndelay(400); >> + kona_pwmc_write_settings(kp, chan, 0, 0, 0); >> + kona_pwmc_set_polarity(chip, pwm, PWM_POLARITY_NORMAL); > > This is wrong. You shouldn't change the polarity when the PWM is disabled. Agreed. No need to set polarity on disable. > > The original polarity isn't even restored when it is re-enabled... > >> + kona_pwmc_set_trigger(kp, chan); >> >> clk_disable_unprepare(kp->clk); >> } >> -- >> 2.1.3 >> > -- > 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/ > -- 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/