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

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Message-ID: <20211110090338.GE12195@pengutronix.de>
Date:   Wed, 10 Nov 2021 10:03:38 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     minyard@....org
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 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.

> ---
>  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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