linux-kernel - Re: [PATCH 3/3] i2c:imx: Use an hrtimer, not a timer, for checking for bus idle

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Date:   Wed, 10 Nov 2021 08:45:45 -0600
From:   Corey Minyard <minyard@....org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-i2c@...r.kernel.org,
        Andrew Manley <andrew.manley@...lingtech.com>,
        linux-kernel@...r.kernel.org, Corey Minyard <cminyard@...sta.com>
Subject: Re: [PATCH 3/3] i2c:imx: Use an hrtimer, not a timer, for checking
 for bus idle

On Wed, Nov 10, 2021 at 10:03:38AM +0100, Oleksij Rempel wrote:
> On Mon, Oct 04, 2021 at 07:32:16PM -0500, minyard@....org wrote:
> > From: Corey Minyard <cminyard@...sta.com>
> > 
> > The timer is too slow and significantly reduces performance.  Use an
> > hrtimer to get things working faster.
> > 
> > Signed-off-by: Corey Minyard <minyard@....org>
> > Tested-by: Andrew Manley <andrew.manley@...lingtech.com>
> > Reviewed-by: Andrew Manley <andrew.manley@...lingtech.com>
> 
> Do we need to keep this change history? If no, please merge it to the
> first patch.

Yeah, I can do that.  It make sense.

Thanks,

-corey

> 
> > ---
> >  drivers/i2c/busses/i2c-imx.c | 23 +++++++++++++++--------
> >  1 file changed, 15 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> > index 26a04dc0590b..4b0e9d1784dd 100644
> > --- a/drivers/i2c/busses/i2c-imx.c
> > +++ b/drivers/i2c/busses/i2c-imx.c
> > @@ -38,7 +38,7 @@
> >  #include <linux/iopoll.h>
> >  #include <linux/kernel.h>
> >  #include <linux/spinlock.h>
> > -#include <linux/timer.h>
> > +#include <linux/hrtimer.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> >  #include <linux/of_device.h>
> > @@ -53,6 +53,8 @@
> >  /* This will be the driver name the kernel reports */
> >  #define DRIVER_NAME "imx-i2c"
> >  
> > +#define I2C_IMX_CHECK_DELAY 30000 /* Time to check for bus idle, in NS */
> > +
> >  /*
> >   * Enable DMA if transfer byte size is bigger than this threshold.
> >   * As the hardware request, it must bigger than 4 bytes.\
> > @@ -214,8 +216,8 @@ struct imx_i2c_struct {
> >  	enum i2c_slave_event last_slave_event;
> >  
> >  	/* For checking slave events. */
> > -	spinlock_t	  slave_lock;
> > -	struct timer_list slave_timer;
> > +	spinlock_t     slave_lock;
> > +	struct hrtimer slave_timer;
> >  };
> >  
> >  static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
> > @@ -783,13 +785,16 @@ static irqreturn_t i2c_imx_slave_handle(struct imx_i2c_struct *i2c_imx,
> >  	}
> >  
> >  out:
> > -	mod_timer(&i2c_imx->slave_timer, jiffies + 1);
> > +	hrtimer_try_to_cancel(&i2c_imx->slave_timer);
> > +	hrtimer_forward_now(&i2c_imx->slave_timer, I2C_IMX_CHECK_DELAY);
> > +	hrtimer_restart(&i2c_imx->slave_timer);
> >  	return IRQ_HANDLED;
> >  }
> >  
> > -static void i2c_imx_slave_timeout(struct timer_list *t)
> > +static enum hrtimer_restart i2c_imx_slave_timeout(struct hrtimer *t)
> >  {
> > -	struct imx_i2c_struct *i2c_imx = from_timer(i2c_imx, t, slave_timer);
> > +	struct imx_i2c_struct *i2c_imx = container_of(t, struct imx_i2c_struct,
> > +						      slave_timer);
> >  	unsigned int ctl, status;
> >  	unsigned long flags;
> >  
> > @@ -798,6 +803,7 @@ static void i2c_imx_slave_timeout(struct timer_list *t)
> >  	ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
> >  	i2c_imx_slave_handle(i2c_imx, status, ctl);
> >  	spin_unlock_irqrestore(&i2c_imx->slave_lock, flags);
> > +	return HRTIMER_NORESTART;
> >  }
> >  
> >  static void i2c_imx_slave_init(struct imx_i2c_struct *i2c_imx)
> > @@ -1423,7 +1429,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
> >  		return -ENOMEM;
> >  
> >  	spin_lock_init(&i2c_imx->slave_lock);
> > -	timer_setup(&i2c_imx->slave_timer, i2c_imx_slave_timeout, 0);
> > +	hrtimer_init(&i2c_imx->slave_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
> > +	i2c_imx->slave_timer.function = i2c_imx_slave_timeout;
> >  
> >  	match = device_get_match_data(&pdev->dev);
> >  	if (match)
> > @@ -1538,7 +1545,7 @@ static int i2c_imx_remove(struct platform_device *pdev)
> >  	if (ret < 0)
> >  		return ret;
> >  
> > -	del_timer_sync(&i2c_imx->slave_timer);
> > +	hrtimer_cancel(&i2c_imx->slave_timer);
> >  
> >  	/* remove adapter */
> >  	dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n");
> > -- 
> > 2.25.1
> > 
> > 
> 
> -- 
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