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

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Date:   Mon, 6 Sep 2021 23:25:12 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: analog: Always use ktime functions

On 9/6/21 10:59 PM, Dmitry Torokhov wrote:
> 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.
> 

Will do.

>>   }
>>   
>>   /*
>> @@ -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.
> 

Sure. I'll just use NSEC_PER_MSEC directly.

Thanks,
Guenter