Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754750AbbFLV3h (ORCPT ); Fri, 12 Jun 2015 17:29:37 -0400 Received: from mail-gw3-out.broadcom.com ([216.31.210.64]:16682 "EHLO mail-gw3-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751362AbbFLV3f (ORCPT ); Fri, 12 Jun 2015 17:29:35 -0400 X-IronPort-AV: E=Sophos;i="5.13,604,1427785200"; d="scan'208";a="67157065" Message-ID: <557B4F3D.2000001@broadcom.com> Date: Fri, 12 Jun 2015 14:29:33 -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: Tim Kryger CC: Dmitry Torokhov , Anatol Pomazau , Arun Ramamurthy , Thierry Reding , Scott Branden , bcm-kernel-feedback-list , "Linux Kernel Mailing List" , Linux PWM Subject: Re: [PATCH v8 4/5] pwm: kona: Add debug info to config function References: <1432670900-27687-1-git-send-email-jonathar@broadcom.com> <1432670900-27687-5-git-send-email-jonathar@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 Content-Length: 3934 Lines: 97 On 15-05-30 09:42 AM, Tim Kryger wrote: > On Tue, May 26, 2015 at 1:08 PM, Jonathan Richardson > wrote: >> Adds debugging info to config function where duty cycle and period >> are calculated and verified. >> >> Signed-off-by: Jonathan Richardson >> --- >> drivers/pwm/pwm-bcm-kona.c | 25 +++++++++++++++++++++++-- >> 1 file changed, 23 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c >> index c87621f..0ddf19b 100644 >> --- a/drivers/pwm/pwm-bcm-kona.c >> +++ b/drivers/pwm/pwm-bcm-kona.c >> @@ -138,18 +138,39 @@ static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm, >> dc = div64_u64(val, div); >> >> /* If duty_ns or period_ns are not achievable then return */ >> - if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN) > > The original code was based on the SPEAr PWM driver which has a non-zero > PWMDCR_MIN_DUTY such that the second condition here can evaluate to true. > > This isn't the case for the Kona PWM where DUTY_CYCLE_HIGH_MIN is zero. > >> + if (pc < PERIOD_COUNT_MIN) { >> + dev_warn(chip->dev, >> + "%s: pwm[%d]: period=%d is not achievable, pc=%lu, prescale=%lu\n", >> + __func__, chan, period_ns, pc, prescale); >> return -EINVAL; >> + } > > Why not just print the minimum allowable period with the provided clock? > > I don't think pc and prescale will be particularly helpful to users. > > Also, do we really need to print __func__ here? > >> + >> + if (dc < DUTY_CYCLE_HIGH_MIN) { >> + if (0 != duty_ns) { >> + dev_warn(chip->dev, >> + "%s: pwm[%d]: duty cycle=%d is not achievable, dc=%lu, prescale=%lu\n", >> + __func__, chan, duty_ns, dc, prescale); >> + } >> + return -EINVAL; >> + } > > The above block is unreachable code. > >> >> /* If pc and dc are in bounds, the calculation is done */ >> if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX) >> break; >> >> /* Otherwise, increase prescale and recalculate pc and dc */ >> - if (++prescale > PRESCALE_MAX) >> + if (++prescale > PRESCALE_MAX) { >> + dev_warn(chip->dev, >> + "%s: pwm[%d]: Prescale (=%lu) within max (=%d) for period=%d and duty cycle=%d is not achievable\n", >> + __func__, chan, prescale, PRESCALE_MAX, >> + period_ns, duty_ns); >> return -EINVAL; >> + } >> } > > The user got here because they specified a period larger than the maximum > supported so why not tell them largest value that can be supported instead > of confusing them with prescale and PRESCALE_MAX? > >> >> + dev_dbg(chip->dev, "pwm[%d]: period=%lu, duty_high=%lu, prescale=%lu\n", >> + chan, pc, dc, prescale); >> + > > This could be more clear. It prints pc but calls it period. > >> /* >> * Don't apply settings if disabled. The period and duty cycle are >> * always calculated above to ensure the new values are >> -- >> 1.7.9.5 >> We can defer this for now until I can look into it further. It's not a priority. I'm more concerned with core changes and kona pwm fix. Thanks, Jon -- 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/