From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olliver Schinagl Subject: Re: [PATCH 08/10] pwm: core: add pulse feature to the PWM framework Date: Fri, 06 Nov 2015 16:46:54 +0100 Message-ID: <563CCB6E.2090206@ultimaker.com> References: <1445895161-2317-1-git-send-email-o.schinagl@ultimaker.com> <1445895161-2317-9-git-send-email-o.schinagl@ultimaker.com> <20151106151816.GD8418@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20151106151816.GD8418@ulmo> Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding Cc: Olliver Schinagl , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Joachim Eastwood , Maxime Ripard , Alexandre Belloni , Olliver Schinagl , linux-pwm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-pwm@vger.kernel.org Hey Thierry, On 06-11-15 16:18, Thierry Reding wrote: > On Mon, Oct 26, 2015 at 10:32:39PM +0100, Olliver Schinagl wrote: >> From: Olliver Schinagl >> >> Some hardware PWM's have the possibility to only send out one (or mo= re) >> pulses. This can be quite a useful feature in case one wants or need= s >> only a single pulse, but at the exact width. >> >> Additionally, if multiple pulses are possible, outputting a fixed am= ount >> of pulses can be useful for various timing specific purposes. > I see how theoretically this would be nice to have. But I'm reluctant= to > merge this feature if there aren't any users. What drivers in the ker= nel > would want to use this feature? Are there new drivers being worked on > that will need this? I should have brought this up as to why I added this, I'm working on a=20 stepper driver framework (inspired by the pwm framework actually) and=20 rotating moters by x degree's you do by sending pulses, using controlle= d=20 pulses (timing wise) you can precisely move stepper motors. Yes we can=20 do this reasonably accurate in software, but doing it in hardware is so= =20 much nicer. > >> A few new functions have been expanded or added for this new behavio= r. >> >> * pwm_config() now takes an additional parameter to setup the number= of >> pulses to output. The driver may force this to 0 or 1 >> for if example if this feature is not or only partially >> supported > This is problematic because you need to atomically update all drivers > and users (the kbuild robot already told you that you didn't do this)= =2E > To make things easier I suggest you wait with this change until the > atomic PWM patches have been merged, at which point it should become = a > lot easier to deal with this kind of extension. yes, I think i mentioned this in the cover letter, I wanted to get your= =20 input whilst waiting for Boris's patches. So I deffinatly want to=20 combine it then, just getting some head work started :) > >> * pwm_[sg]et_pulse_count() get or set the number of pulses the pwm >> framework is configured for >> * pwm_get_pulse_count_max() get the maximum number of pulses the pwm >> driver supports >> * pwm_pulse() Tell the PWM to emit a pre-configured number of pulse= s > Isn't this essentially the same as pwm_enable()? I'd think that if th= e > PWM is configured to output pulses, then pwm_enable() would simply do > what it's been configured to do (emit the pulses). Why the need for a= n > additional function? pwm_pulse() should be dropped, I think I accidentally left that in the=20 documentation, sorry. > >> * pwm_pulse_done() an internal function for drivers to call when >> they have completed their pre-configured number >> of pulses >> * pwm_is_pulsing() tells the callers if the pwm is busy pulsing, >> yielding a little more information than just >> pwm_is_enabled() > Similarily, I'd think that once the PWM is done executing the series = of > pulses that it was configured for it would be automatically disabled.= A > consumer could then simply use pwm_is_enabled() and drivers could cal= l > pwm_disable() on their PWM to mark them as disabled when they're done > pulsing. I agree, pulseating can be dropped too as we know that a) the pulse fla= g=20 is set, b) we are enabled. But I'm not sure now if the flag is exported= =20 to sysfs, in any case, sysfs should just check the pulseating flag? > >> Signed-off-by: Olliver Schinagl >> --- >> drivers/pwm/core.c | 30 +++++++++++++++++++---- >> drivers/pwm/pwm-gpio.c | 3 ++- >> drivers/pwm/pwm-sun4i.c | 3 ++- >> drivers/pwm/sysfs.c | 58 +++++++++++++++++++++++++++++++++++++= +++++-- >> include/linux/pwm.h | 64 +++++++++++++++++++++++++++++++++++++= +++++++++--- >> 5 files changed, 147 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c >> index 3f9df3e..e2c1c0a 100644 >> --- a/drivers/pwm/core.c >> +++ b/drivers/pwm/core.c >> @@ -432,22 +432,29 @@ EXPORT_SYMBOL_GPL(pwm_free); >> * @pwm: PWM device >> * @duty_ns: "on" time (in nanoseconds) >> * @period_ns: duration (in nanoseconds) of one cycle >> + * @pulse_count: number of pulses (periods) to output on pwm_pulse >> * >> * Returns: 0 on success or a negative error code on failure. >> */ >> -int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns) >> +int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns, >> + unsigned int pulse_count) > Like I said, this is problematic because every driver and every consu= mer > now needs to be aware of pulsing. Once the PWM atomic patches are mer= ged > this will become easier to do because the pulse configuration would b= e a > part of the atomic state, and hence can be conveniently ignored by us= ers > and driver alike. I agree :) I'll take your initial comments and work with those so far i= n=20 cleaning stuff up. Feel free to get back to me about the validity of th= e=20 pwm_pulse for steppers generally > Thierry --=20 Met vriendelijke groeten, Kind regards, =E4=B8=8E=E4=BA=B2=E5=88=87=E7=9A= =84=E9=97=AE=E5=80=99 Olliver Schinagl Software Engineer Research & Development Ultimaker B.V. From mboxrd@z Thu Jan 1 00:00:00 1970 From: o.schinagl@ultimaker.com (Olliver Schinagl) Date: Fri, 06 Nov 2015 16:46:54 +0100 Subject: [PATCH 08/10] pwm: core: add pulse feature to the PWM framework In-Reply-To: <20151106151816.GD8418@ulmo> References: <1445895161-2317-1-git-send-email-o.schinagl@ultimaker.com> <1445895161-2317-9-git-send-email-o.schinagl@ultimaker.com> <20151106151816.GD8418@ulmo> Message-ID: <563CCB6E.2090206@ultimaker.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hey Thierry, On 06-11-15 16:18, Thierry Reding wrote: > On Mon, Oct 26, 2015 at 10:32:39PM +0100, Olliver Schinagl wrote: >> From: Olliver Schinagl >> >> Some hardware PWM's have the possibility to only send out one (or more) >> pulses. This can be quite a useful feature in case one wants or needs >> only a single pulse, but at the exact width. >> >> Additionally, if multiple pulses are possible, outputting a fixed amount >> of pulses can be useful for various timing specific purposes. > I see how theoretically this would be nice to have. But I'm reluctant to > merge this feature if there aren't any users. What drivers in the kernel > would want to use this feature? Are there new drivers being worked on > that will need this? I should have brought this up as to why I added this, I'm working on a stepper driver framework (inspired by the pwm framework actually) and rotating moters by x degree's you do by sending pulses, using controlled pulses (timing wise) you can precisely move stepper motors. Yes we can do this reasonably accurate in software, but doing it in hardware is so much nicer. > >> A few new functions have been expanded or added for this new behavior. >> >> * pwm_config() now takes an additional parameter to setup the number of >> pulses to output. The driver may force this to 0 or 1 >> for if example if this feature is not or only partially >> supported > This is problematic because you need to atomically update all drivers > and users (the kbuild robot already told you that you didn't do this). > To make things easier I suggest you wait with this change until the > atomic PWM patches have been merged, at which point it should become a > lot easier to deal with this kind of extension. yes, I think i mentioned this in the cover letter, I wanted to get your input whilst waiting for Boris's patches. So I deffinatly want to combine it then, just getting some head work started :) > >> * pwm_[sg]et_pulse_count() get or set the number of pulses the pwm >> framework is configured for >> * pwm_get_pulse_count_max() get the maximum number of pulses the pwm >> driver supports >> * pwm_pulse() Tell the PWM to emit a pre-configured number of pulses > Isn't this essentially the same as pwm_enable()? I'd think that if the > PWM is configured to output pulses, then pwm_enable() would simply do > what it's been configured to do (emit the pulses). Why the need for an > additional function? pwm_pulse() should be dropped, I think I accidentally left that in the documentation, sorry. > >> * pwm_pulse_done() an internal function for drivers to call when >> they have completed their pre-configured number >> of pulses >> * pwm_is_pulsing() tells the callers if the pwm is busy pulsing, >> yielding a little more information than just >> pwm_is_enabled() > Similarily, I'd think that once the PWM is done executing the series of > pulses that it was configured for it would be automatically disabled. A > consumer could then simply use pwm_is_enabled() and drivers could call > pwm_disable() on their PWM to mark them as disabled when they're done > pulsing. I agree, pulseating can be dropped too as we know that a) the pulse flag is set, b) we are enabled. But I'm not sure now if the flag is exported to sysfs, in any case, sysfs should just check the pulseating flag? > >> Signed-off-by: Olliver Schinagl >> --- >> drivers/pwm/core.c | 30 +++++++++++++++++++---- >> drivers/pwm/pwm-gpio.c | 3 ++- >> drivers/pwm/pwm-sun4i.c | 3 ++- >> drivers/pwm/sysfs.c | 58 ++++++++++++++++++++++++++++++++++++++++++-- >> include/linux/pwm.h | 64 ++++++++++++++++++++++++++++++++++++++++++++++--- >> 5 files changed, 147 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c >> index 3f9df3e..e2c1c0a 100644 >> --- a/drivers/pwm/core.c >> +++ b/drivers/pwm/core.c >> @@ -432,22 +432,29 @@ EXPORT_SYMBOL_GPL(pwm_free); >> * @pwm: PWM device >> * @duty_ns: "on" time (in nanoseconds) >> * @period_ns: duration (in nanoseconds) of one cycle >> + * @pulse_count: number of pulses (periods) to output on pwm_pulse >> * >> * Returns: 0 on success or a negative error code on failure. >> */ >> -int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns) >> +int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns, >> + unsigned int pulse_count) > Like I said, this is problematic because every driver and every consumer > now needs to be aware of pulsing. Once the PWM atomic patches are merged > this will become easier to do because the pulse configuration would be a > part of the atomic state, and hence can be conveniently ignored by users > and driver alike. I agree :) I'll take your initial comments and work with those so far in cleaning stuff up. Feel free to get back to me about the validity of the pwm_pulse for steppers generally > Thierry -- Met vriendelijke groeten, Kind regards, ?????? Olliver Schinagl Software Engineer Research & Development Ultimaker B.V.