From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Cercueil Subject: Re: [PATCH v2 1/3] pwm: jz4740: Use clocks from TCU driver Date: Mon, 18 Nov 2019 11:55:56 +0100 Message-ID: <1574074556.3.0@crapouillou.net> References: <20191116173613.72647-1-paul@crapouillou.net> <20191116173613.72647-2-paul@crapouillou.net> <20191117202028.4chgjv2kulyyq2eu@pengutronix.de> <1574031523.3.0@crapouillou.net> <20191118071538.46egokrswvjxdvfp@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20191118071538.46egokrswvjxdvfp@pengutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: Uwe =?iso-8859-1?q?Kleine-K=F6nig?= Cc: Thierry Reding , od@zcrc.me, linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, Mathieu Malaterre , Artur Rojek , kernel@pengutronix.de List-Id: linux-pwm@vger.kernel.org Hi Uwe, Le lun., nov. 18, 2019 at 08:15, Uwe Kleine-K=F6nig=20 a =E9crit : > Hello Paul, >=20 > On Sun, Nov 17, 2019 at 11:58:43PM +0100, Paul Cercueil wrote: >> Le dim., nov. 17, 2019 at 21:20, Uwe Kleine-K=F6nig >> a =E9crit : >> > On Sat, Nov 16, 2019 at 06:36:11PM +0100, Paul Cercueil wrote: >> > > The ingenic-timer "TCU" driver provides us with clocks, that=20 >> can be >> > > (un)gated, reparented or reclocked from devicetree, instead of=20 >> having >> > > these settings hardcoded in this driver. >> > > >> > > While this driver is devicetree-compatible, it is never (as of=20 >> now) >> > > probed from devicetree, so this change does not introduce a=20 >> ABI problem >> > > with current devicetree files. >> > > >> > > Signed-off-by: Paul Cercueil >> > > Tested-by: Mathieu Malaterre >> > > Tested-by: Artur Rojek >> > > --- >> > > >> > > Notes: >> > > v2: This patch is now before the patch introducing regmap,=20 >> so >> > > the code >> > > has changed a bit. >> > > >> > > drivers/pwm/Kconfig | 1 + >> > > drivers/pwm/pwm-jz4740.c | 45=20 >> ++++++++++++++++++++++++++++------------ >> > > 2 files changed, 33 insertions(+), 13 deletions(-) >> > > >> > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig >> > > index e3a2518503ed..e998e5cb01b0 100644 >> > > --- a/drivers/pwm/Kconfig >> > > +++ b/drivers/pwm/Kconfig >> > > @@ -225,6 +225,7 @@ config PWM_IMX_TPM >> > > config PWM_JZ4740 >> > > tristate "Ingenic JZ47xx PWM support" >> > > depends on MACH_INGENIC >> > > + depends on COMMON_CLK >> > > help >> > > Generic PWM framework driver for Ingenic JZ47xx based >> > > machines. >> > > diff --git a/drivers/pwm/pwm-jz4740.c=20 >> b/drivers/pwm/pwm-jz4740.c >> > > index 9d78cc21cb12..fd83644f9323 100644 >> > > --- a/drivers/pwm/pwm-jz4740.c >> > > +++ b/drivers/pwm/pwm-jz4740.c >> > > @@ -24,7 +24,6 @@ >> > > >> > > struct jz4740_pwm_chip { >> > > struct pwm_chip chip; >> > > - struct clk *clk; >> > >> > What is the motivation to go away from this approach to store the=20 >> clock? >>=20 >> It's actually not the same clock. Instead of obtaining "ext" clock=20 >> from the >> probe, we obtain "timerX" clocks (X being the PWM channel) from the=20 >> request >> callback. >=20 > Before you used driver data and container_of to get it, now you used > pwm_set_chip_data. I wondered why you changed the approach to store > data. That the actual data is different now is another thing (and > obviously ok). Thierry suggested it: https://lkml.org/lkml/2019/3/4/486 >=20 >> > > }; >> > > >> > > static inline struct jz4740_pwm_chip *to_jz4740(struct=20 >> pwm_chip *chip) >> > > @@ -34,6 +33,11 @@ static inline struct jz4740_pwm_chip=20 >> *to_jz4740(struct pwm_chip *chip) >> > > >> > > static int jz4740_pwm_request(struct pwm_chip *chip, struct=20 >> pwm_device *pwm) >> > > { >> > > + struct jz4740_pwm_chip *jz =3D to_jz4740(chip); >> > > + struct clk *clk; >> > > + char clk_name[16]; >> > > + int ret; >> > > + >> > > /* >> > > * Timers 0 and 1 are used for system tasks, so they are=20 >> unavailable >> > > * for use as PWMs. >> > > @@ -41,16 +45,31 @@ static int jz4740_pwm_request(struct=20 >> pwm_chip *chip, struct pwm_device *pwm) >> > > if (pwm->hwpwm < 2) >> > > return -EBUSY; >> > > >> > > - jz4740_timer_start(pwm->hwpwm); >> > > + snprintf(clk_name, sizeof(clk_name), "timer%u", pwm->hwpwm); >> > > + >> > > + clk =3D clk_get(chip->dev, clk_name); >> > > + if (IS_ERR(clk)) >> > >> > if (PTR_ERR(clk) !=3D -EPROBE_DEFER) >> > dev_err(chip->dev, "Failed to get clock: %pe\n", clk); >>=20 >> Never heard about that %pe. Will do that. >=20 > Yeah, that's new and IMHO quite nice. >=20 >> > > + return PTR_ERR(clk); >> > > + >> > > + ret =3D clk_prepare_enable(clk); >> > > + if (ret) { >> > > + clk_put(clk); >> > > + return ret; >> > > + } >> > > + >> > > + pwm_set_chip_data(pwm, clk); >> > > >> > > return 0; >> > > } >> > > >> > > static void jz4740_pwm_free(struct pwm_chip *chip, struct=20 >> pwm_device *pwm) >> > > { >> > > + struct clk *clk =3D pwm_get_chip_data(pwm); >> > > + >> > > jz4740_timer_set_ctrl(pwm->hwpwm, 0); >> > >> > What is the purpose of this call? I would have expected that all=20 >> these >> > would go away when converting to the clk stuff?! >>=20 >> Some go away in patch [1/3] as they are clock-related, this one=20 >> will go away >> in patch [2/3] when the driver is converted to use regmap. >=20 > I'd like to understand what it does. Judging from the name I expect=20 > this > is somehow related to the clock stuff and so I wonder if the=20 > conversion > to the clk API is as complete as it should be. It clears the PWM channel's CTRL register. That's the register used for=20 instance to enable the PWM function of a TCU channel. >=20 >> > > - jz4740_timer_stop(pwm->hwpwm); >> > > + clk_disable_unprepare(clk); >> > > + clk_put(clk); >> > > } >> > > >> > > static int jz4740_pwm_enable(struct pwm_chip *chip, struct=20 >> pwm_device *pwm) >> > > @@ -91,17 +110,21 @@ static int jz4740_pwm_apply(struct=20 >> pwm_chip *chip, struct pwm_device *pwm, >> > > const struct pwm_state *state) >> > > { >> > > struct jz4740_pwm_chip *jz4740 =3D to_jz4740(pwm->chip); >> > > + struct clk *clk =3D pwm_get_chip_data(pwm), >> > > + *parent_clk =3D clk_get_parent(clk); >> > > + unsigned long rate, period, duty; >> > > unsigned long long tmp; >> > > - unsigned long period, duty; >> > > unsigned int prescaler =3D 0; >> > > uint16_t ctrl; >> > > >> > > - tmp =3D (unsigned long long)clk_get_rate(jz4740->clk) *=20 >> state->period; >> > > + rate =3D clk_get_rate(parent_clk); >> > >> > Why is it the parent's rate that is relevant here? >>=20 >> We calculate the divider to be used for the "timerX" clock, so we=20 >> need to >> know the parent clock. >=20 > Then the approach here is wrong. You should not assume anything about > the internal details of the clock, that's the task of the clock=20 > driver. > As a consumer of the clock just request a rate (or use clk_round_rate=20 > to > find a good setting first) and use that. Totally agreed. I wanted to do that, but you were fighting tooth and=20 nails against my patch "Improve algorithm of clock calculation",=20 remember? -Paul =