linux-kernel - Re: [PATCH v6 4/4] media: pwm-ir-tx: trigger edges from hrtimer interrupt context

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Date:   Sat, 9 Dec 2023 09:52:09 +0000
From:   Sean Young <sean@...s.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     linux-media@...r.kernel.org, linux-pwm@...r.kernel.org,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 4/4] media: pwm-ir-tx: trigger edges from hrtimer
 interrupt context

On Fri, Dec 08, 2023 at 05:29:55PM +0100, Thierry Reding wrote:
> On Wed, Nov 29, 2023 at 09:13:37AM +0000, Sean Young wrote:
> > This makes the generated IR much more precise. Before this change, the
> > driver is unreliable and many users opted to use gpio-ir-tx instead.
> > 
> > Signed-off-by: Sean Young <sean@...s.org>
> > ---
> >  drivers/media/rc/pwm-ir-tx.c | 79 ++++++++++++++++++++++++++++++++++--
> >  1 file changed, 76 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c
> > index cf51e2760975..8575c4596d7b 100644
> > --- a/drivers/media/rc/pwm-ir-tx.c
> > +++ b/drivers/media/rc/pwm-ir-tx.c
> > @@ -10,6 +10,8 @@
> >  #include <linux/slab.h>
> >  #include <linux/of.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/hrtimer.h>
> > +#include <linux/completion.h>
> >  #include <media/rc-core.h>
> >  
> >  #define DRIVER_NAME	"pwm-ir-tx"
> > @@ -17,8 +19,14 @@
> >  
> >  struct pwm_ir {
> >  	struct pwm_device *pwm;
> > -	unsigned int carrier;
> > -	unsigned int duty_cycle;
> > +	struct hrtimer timer;
> > +	struct completion tx_done;
> > +	struct pwm_state *state;
> > +	u32 carrier;
> > +	u32 duty_cycle;
> > +	uint *txbuf;
> 
> Maybe mark this as const to signal that it's not going to get modified?

Ah nice, I usually forget const. 

> > +	uint txbuf_len;
> > +	uint txbuf_index;
> 
> uint is rather rare. Or so I thought. There seem to be quite a few
> occurrences throughout the kernel. I'd still prefer unsigned int over
> this abbreviated form, but ultimately up to you and Mauro to decide.

Yes, unsigned int is used a lot more. Changed.

> >  static int pwm_ir_probe(struct platform_device *pdev)
> >  {
> >  	struct pwm_ir *pwm_ir;
> > @@ -103,10 +167,19 @@ static int pwm_ir_probe(struct platform_device *pdev)
> >  	if (!rcdev)
> >  		return -ENOMEM;
> >  
> > +	if (pwm_is_atomic(pwm_ir->pwm)) {
> > +		init_completion(&pwm_ir->tx_done);
> > +		hrtimer_init(&pwm_ir->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> > +		pwm_ir->timer.function = pwm_ir_timer;
> > +		rcdev->tx_ir = pwm_ir_tx_atomic;
> > +	} else {
> > +		dev_info(&pdev->dev, "tx will not be accurate as pwm device does not support atomic mode");
> 
> s/tx/TX and s/pwm/PWM/? Also, I'm a bit unhappy about "atomic mode" here
> because the term is overloaded in PWM. If you call pwm_appy_*() then by
> definition it's going to be "atomic" in the "atomic state" sense. So
> maybe switch to something like:
> 
> 	"TX will not be accurate as PWM device might sleep"
> 
> ?

Very nice, changed.

Thanks
Sean