Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753519AbbGBXgr (ORCPT ); Thu, 2 Jul 2015 19:36:47 -0400 Received: from mail-gw1-out.broadcom.com ([216.31.210.62]:39384 "EHLO mail-gw1-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752614AbbGBXgk (ORCPT ); Thu, 2 Jul 2015 19:36:40 -0400 X-IronPort-AV: E=Sophos;i="5.15,395,1432623600"; d="scan'208";a="69104587" Message-ID: <5595CB06.6060005@broadcom.com> Date: Thu, 2 Jul 2015 16:36:38 -0700 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: Jonathan Richardson CC: Tim Kryger , Dmitry Torokhov , Anatol Pomazau , Arun Ramamurthy , Thierry Reding , Scott Branden , bcm-kernel-feedback-list , , Subject: Re: [PATCH v9 1/2] pwm: kona: Modify settings application sequence References: <1434403262-24198-1-git-send-email-jonathar@broadcom.com> <1434403262-24198-2-git-send-email-jonathar@broadcom.com> In-Reply-To: <1434403262-24198-2-git-send-email-jonathar@broadcom.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4770 Lines: 132 Hi Theirry, If there are no more comments can this patch be applied? Thanks, Jon On 15-06-15 02:21 PM, Jonathan Richardson wrote: > 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); > } > -- 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/