linux-kernel - Re: [PATCH] fbdev: radeon: Remove 'struct timeval' usage

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Date:	Fri, 5 Jun 2015 14:40:36 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>
Cc:	Tina Ruchandani <ruchandani.tina@...il.com>,
	Arnd Bergmann <arnd@...db.de>, y2038@...ts.linaro.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fbdev: radeon: Remove 'struct timeval' usage

On 3 June 2015 at 21:59, Tomi Valkeinen <tomi.valkeinen@...com> wrote:
>
>
> On 25/05/15 07:07, Tina Ruchandani wrote:
>> 'struct timeval' uses a 32-bit representation for the
>> seconds field which will overflow in the year 2038 and beyond.
>> This patch replaces the usage of 'struct timeval' with
>> ktime_t which uses a 64-bit time representation and does not
>> suffer from the y2038 problem. This patch is part of a larger
>> effort to remove all instances of 'struct timeval', 'struct
>> timespec', time_t and other 32-bit timekeeping variables
>> from the kernel.
>> The patch also replaces the use of real time (do_gettimeofday)
>> with monotonic time (ktime_get).
>>
>> Signed-off-by: Tina Ruchandani <ruchandani.tina@...il.com>
>> ---
>>  drivers/video/fbdev/aty/radeon_base.c | 29 ++++++++++++++---------------
>>  1 file changed, 14 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/video/fbdev/aty/radeon_base.c b/drivers/video/fbdev/aty/radeon_base.c
>> index 01237c8..9747e9e 100644
>> --- a/drivers/video/fbdev/aty/radeon_base.c
>> +++ b/drivers/video/fbdev/aty/radeon_base.c
>> @@ -64,6 +64,7 @@
>>  #include <linux/slab.h>
>>  #include <linux/delay.h>
>>  #include <linux/time.h>
>> +#include <linux/ktime.h>
>>  #include <linux/fb.h>
>>  #include <linux/ioport.h>
>>  #include <linux/init.h>
>> @@ -461,8 +462,8 @@ static int radeon_probe_pll_params(struct radeonfb_info *rinfo)
>>       int hTotal, vTotal, num, denom, m, n;
>>       unsigned long long hz, vclk;
>>       long xtal;
>> -     struct timeval start_tv, stop_tv;
>> -     long total_secs, total_usecs;
>> +     ktime_t start, stop;
>> +     s64 delta;
>>       int i;
>>
>>       /* Ugh, we cut interrupts, bad bad bad, but we want some precision
>> @@ -478,7 +479,7 @@ static int radeon_probe_pll_params(struct radeonfb_info *rinfo)
>>               if (((INREG(CRTC_VLINE_CRNT_VLINE) >> 16) & 0x3ff) == 0)
>>                       break;
>>
>> -     do_gettimeofday(&start_tv);
>> +     start = ktime_get();
>>
>>       for(i=0; i<1000000; i++)
>>               if (((INREG(CRTC_VLINE_CRNT_VLINE) >> 16) & 0x3ff) != 0)
>> @@ -487,20 +488,18 @@ static int radeon_probe_pll_params(struct radeonfb_info *rinfo)
>>       for(i=0; i<1000000; i++)
>>               if (((INREG(CRTC_VLINE_CRNT_VLINE) >> 16) & 0x3ff) == 0)
>>                       break;
>> -
>> -     do_gettimeofday(&stop_tv);
>> -
>> +
>> +     stop = ktime_get();
>> +
>>       local_irq_enable();
>>
>> -     total_secs = stop_tv.tv_sec - start_tv.tv_sec;
>> -     if (total_secs > 10)
>> +     delta = ktime_us_delta(stop, start);
>> +
>> +     /* Return -1 if more than 10 seconds have elapsed */
>> +     if (delta > (10*1000000))
>>               return -1;
>> -     total_usecs = stop_tv.tv_usec - start_tv.tv_usec;
>> -     total_usecs += total_secs * 1000000;
>> -     if (total_usecs < 0)
>> -             total_usecs = -total_usecs;
>> -     hz = 1000000/total_usecs;
>> -
>> +     hz = 1000000/delta;

This needs to be on of the do_div family.

Dave.
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