linux-kernel - Re: [PATCH] Input: analog: Always use ktime functions

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Message-ID: <YTb/t2Qn0BklAlpk@google.com>
Date:   Mon, 6 Sep 2021 22:59:19 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: analog: Always use ktime functions

Hi Guenter,

On Mon, Sep 06, 2021 at 10:06:06PM -0700, Guenter Roeck wrote:
> m68k, mips, s390, and sparc allmodconfig images fail to build with the
> following error.
> 
> drivers/input/joystick/analog.c:160:2: error:
> 	#warning Precise timer not defined for this architecture.
> 
> Remove architecture specific time handling code and always use ktime
> functions to determine time deltas. Also remove the now useless use_ktime
> kernel parameter.
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/input/joystick/analog.c | 74 ++-------------------------------
>  1 file changed, 3 insertions(+), 71 deletions(-)
> 
> diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
> index f798922a4598..4702982182fa 100644
> --- a/drivers/input/joystick/analog.c
> +++ b/drivers/input/joystick/analog.c
> @@ -28,10 +28,6 @@ MODULE_AUTHOR("Vojtech Pavlik <vojtech@....cz>");
>  MODULE_DESCRIPTION(DRIVER_DESC);
>  MODULE_LICENSE("GPL");
>  
> -static bool use_ktime = true;
> -module_param(use_ktime, bool, 0400);
> -MODULE_PARM_DESC(use_ktime, "Use ktime for measuring I/O speed");
> -
>  /*
>   * Option parsing.
>   */
> @@ -119,64 +115,14 @@ struct analog_port {
>  	int axtime;
>  };
>  
> -/*
> - * Time macros.
> - */
> -
> -#ifdef __i386__
> -
> -#include <linux/i8253.h>
> -
> -#define GET_TIME(x)	do { if (boot_cpu_has(X86_FEATURE_TSC)) x = (unsigned int)rdtsc(); else x = get_time_pit(); } while (0)
> -#define DELTA(x,y)	(boot_cpu_has(X86_FEATURE_TSC) ? ((y) - (x)) : ((x) - (y) + ((x) < (y) ? PIT_TICK_RATE / HZ : 0)))
> -#define TIME_NAME	(boot_cpu_has(X86_FEATURE_TSC)?"TSC":"PIT")
> -static unsigned int get_time_pit(void)
> -{
> -        unsigned long flags;
> -        unsigned int count;
> -
> -        raw_spin_lock_irqsave(&i8253_lock, flags);
> -        outb_p(0x00, 0x43);
> -        count = inb_p(0x40);
> -        count |= inb_p(0x40) << 8;
> -        raw_spin_unlock_irqrestore(&i8253_lock, flags);
> -
> -        return count;
> -}
> -#elif defined(__x86_64__)
> -#define GET_TIME(x)	do { x = (unsigned int)rdtsc(); } while (0)
> -#define DELTA(x,y)	((y)-(x))
> -#define TIME_NAME	"TSC"
> -#elif defined(__alpha__) || defined(CONFIG_ARM) || defined(CONFIG_ARM64) || defined(CONFIG_PPC) || defined(CONFIG_RISCV)
> -#define GET_TIME(x)	do { x = get_cycles(); } while (0)
> -#define DELTA(x,y)	((y)-(x))
> -#define TIME_NAME	"get_cycles"
> -#else
> -#define FAKE_TIME
> -static unsigned long analog_faketime = 0;
> -#define GET_TIME(x)     do { x = analog_faketime++; } while(0)
> -#define DELTA(x,y)	((y)-(x))
> -#define TIME_NAME	"Unreliable"
> -#warning Precise timer not defined for this architecture.
> -#endif
> -
>  static inline u64 get_time(void)
>  {
> -	if (use_ktime) {
> -		return ktime_get_ns();
> -	} else {
> -		unsigned int x;
> -		GET_TIME(x);
> -		return x;
> -	}
> +	return ktime_get_ns();
>  }
>  
>  static inline unsigned int delta(u64 x, u64 y)
>  {
> -	if (use_ktime)
> -		return y - x;
> -	else
> -		return DELTA((unsigned int)x, (unsigned int)y);
> +	return y - x;

I wonder if we should get rid of these wrappers and use ktime_t and
ktime_get(), ktime_sub(), etc directly.

>  }
>  
>  /*
> @@ -378,21 +324,7 @@ static void analog_calibrate_timer(struct analog_port *port)
>  	u64 t1, t2, t3;
>  	unsigned long flags;
>  
> -	if (use_ktime) {
> -		port->speed = 1000000;
> -	} else {
> -		local_irq_save(flags);
> -		t1 = get_time();
> -#ifdef FAKE_TIME
> -		analog_faketime += 830;
> -#endif
> -		mdelay(1);
> -		t2 = get_time();
> -		t3 = get_time();
> -		local_irq_restore(flags);
> -
> -		port->speed = delta(t1, t2) - delta(t2, t3);
> -	}
> +	port->speed = 1000000;

It seems we could get rid of port->speed.

Thanks.

-- 
Dmitry