From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753165AbcL2RIn (ORCPT ); Thu, 29 Dec 2016 12:08:43 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:60756 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752749AbcL2RIl (ORCPT ); Thu, 29 Dec 2016 12:08:41 -0500 Date: Thu, 29 Dec 2016 18:08:38 +0100 From: Boris Brezillon To: Lukasz Majewski Cc: Thierry Reding , Sascha Hauer , Stefan Agner , linux-pwm@vger.kernel.org, Bhuvanchandra DV , linux-kernel@vger.kernel.org, Fabio Estevam , Fabio Estevam , Lothar Wassmann , kernel@pengutronix.de Subject: Re: [PATCH v3 RESEND 07/11] pwm: imx: Provide atomic PWM support for i.MX PWMv2 Message-ID: <20161229180838.66ca218f@bbrezillon> In-Reply-To: <20161229174535.01b87fb7@jawa> References: <1477259146-19167-1-git-send-email-l.majewski@majess.pl> <1482792961-12702-1-git-send-email-l.majewski@majess.pl> <1482792961-12702-8-git-send-email-l.majewski@majess.pl> <20161229172117.523a42a4@bbrezillon> <20161229174535.01b87fb7@jawa> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Lukasz, On Thu, 29 Dec 2016 17:45:35 +0100 Lukasz Majewski wrote: > Hi Boris, > > > Hi Lukasz, > > > > On Mon, 26 Dec 2016 23:55:57 +0100 > > Lukasz Majewski wrote: > > > > > This commit provides apply() callback implementation for i.MX's > > > PWMv2. > > > > > > Suggested-by: Stefan Agner > > > Suggested-by: Boris Brezillon > > > Signed-off-by: Lukasz Majewski > > > Reviewed-by: Boris Brezillon > > > --- > > > Changes for v3: > > > - Remove ipg clock enable/disable functions > > > > > > Changes for v2: > > > - None > > > --- > > > drivers/pwm/pwm-imx.c | 70 > > > +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, > > > 70 insertions(+) > > > > > > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c > > > index ebe9b0c..cd53c05 100644 > > > --- a/drivers/pwm/pwm-imx.c > > > +++ b/drivers/pwm/pwm-imx.c > > > @@ -159,6 +159,75 @@ static void imx_pwm_wait_fifo_slot(struct > > > pwm_chip *chip, } > > > } > > > > > > +static int imx_pwm_apply_v2(struct pwm_chip *chip, struct > > > pwm_device *pwm, > > > + struct pwm_state *state) > > > +{ > > > + unsigned long period_cycles, duty_cycles, prescale; > > > + struct imx_chip *imx = to_imx_chip(chip); > > > + struct pwm_state cstate; > > > + unsigned long long c; > > > + u32 cr = 0; > > > + int ret; > > > + > > > + pwm_get_state(pwm, &cstate); > > > + > > > + c = clk_get_rate(imx->clk_per); > > > + c *= state->period; > > > + > > > + do_div(c, 1000000000); > > > + period_cycles = c; > > > + > > > + prescale = period_cycles / 0x10000 + 1; > > > + > > > + period_cycles /= prescale; > > > + c = (unsigned long long)period_cycles * state->duty_cycle; > > > + do_div(c, state->period); > > > + duty_cycles = c; > > > + > > > + /* > > > + * according to imx pwm RM, the real period value should be > > > + * PERIOD value in PWMPR plus 2. > > > + */ > > > + if (period_cycles > 2) > > > + period_cycles -= 2; > > > + else > > > + period_cycles = 0; > > > + > > > + /* Enable the clock if the PWM is being enabled. */ > > > + if (state->enabled && !cstate.enabled) { > > > + ret = clk_prepare_enable(imx->clk_per); > > > + if (ret) > > > + return ret; > > > + } > > > + > > > + /* > > > + * Wait for a free FIFO slot if the PWM is already > > > enabled, and flush > > > + * the FIFO if the PWM was disabled and is about to be > > > enabled. > > > + */ > > > + if (cstate.enabled) > > > + imx_pwm_wait_fifo_slot(chip, pwm); > > > + else if (state->enabled) > > > + imx_pwm_sw_reset(chip); > > > + > > > + writel(duty_cycles, imx->mmio_base + MX3_PWMSAR); > > > + writel(period_cycles, imx->mmio_base + MX3_PWMPR); > > > + > > > + cr |= MX3_PWMCR_PRESCALER(prescale) | > > > + MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN | > > > + MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH; > > > + > > > + if (state->enabled) > > > + cr |= MX3_PWMCR_EN; > > > + > > > + writel(cr, imx->mmio_base + MX3_PWMCR); > > > + > > > + /* Disable the clock if the PWM is being disabled. */ > > > + if (!state->enabled && cstate.enabled) > > > + clk_disable_unprepare(imx->clk_per); > > > + > > > + return 0; > > > +} > > > + > > > > Stefan suggested to rework this function to avoid unneeded > > duty/period calculation and reg write when disabling the PWM. Why > > didn't you send a v4 addressing that instead of resending the exact > > same v3? > > The discussion between you and Stefan was in this thread: > http://patchwork.ozlabs.org/patch/689790/ > > Stefan proposed change, you replied with your concerns and that is all. Well, regarding the imx_pwm_apply_v2() suggested by Stefan, I think we both agreed that most of the code was unneeded when all we want to do is disable the PWM. My concern was more about the way PWM changes are applied (->apply() returns before the change is actually applied), but I agreed that it could be fixed later on (if other people think it's really needed), since the existing code already handles it this way. > No clear decision what to change until today when Stefan prepared > separate (concise) patch (now I see what is the problem). > The patch proposed by Stefan is addressing a different problem: the periph clock has to be enabled before accessing registers. > > > > > Same goes for the regression introduced in patch 2: I think it's > > better to keep things bisectable on all platforms (even if it > > appeared to work by chance on imx7, it did work before this change). > > Could you be more specific about your idea to solve this problem? Stefan already provided a patch, I just think it should be fixed before patch 2 to avoid breaking bisectibility. > > > > > That's just my opinion, but when you get reviews on a patch series, > > it's better to address them directly (especially when issues can be > > easily fixed) than provide follow-up patches. > > I do not have iMX7 for testing/development, so I could not reproduce > the error and address the issue directly. Well, the description made by Stefan seemed pretty clear to me: you need to enable the periph clock before accessing PWM registers. > > I can at best integrate Stefan's patch and hope to not introduce > regression. You can ask others to test your own patches. In this case, just clearly state that the patch is untested and that you'd like people owning a specific platform to test it. Regards, Boris