[PATCH] Revert "drm: Don't pass negative delta to ktime_sub_ns()"

[Imre Deak]

On Tue, 2016-03-29 at 13:12 +0200, Daniel Vetter wrote:
> This reverts commit e91abf80a0998f326107874c88d549f94839f13c.
> 
> Since
> 
> commit 24e4a8c3e8868874835b0f1ad6dd417341e99822
> Author: John Stultz <john.stultz at linaro.org>
> Date:   Wed Jul 16 21:03:53 2014 +0000
> 
>     ktime: Kill non-scalar ktime_t implementation for 2038
> 
> there is no longer a 32bit version that's unsigned, and we don't have
> to jump through ridiculous hoops to make the calculations correct.
> 
> I didn't look whether there's more of this pattern in the kernel.
> 
> Cc: John Stultz <john.stultz at linaro.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Michel Dänzer <michel.daenzer at amd.com>
> Cc: Imre Deak <imre.deak at intel.com>
> Cc: Dave Airlie <airlied at redhat.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

Reviewed-by: Imre Deak <imre.deak at intel.com>

> ---
>  drivers/gpu/drm/drm_irq.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index f77653562fac..4d06cf41df96 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -863,10 +863,7 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct
> drm_device *dev,
>  	/* Subtract time delta from raw timestamp to get final
>  	 * vblank_time timestamp for end of vblank.
>  	 */
> -	if (delta_ns < 0)
> -		etime = ktime_add_ns(etime, -delta_ns);
> -	else
> -		etime = ktime_sub_ns(etime, delta_ns);
> +	etime = ktime_sub_ns(etime, delta_ns);
>  	*vblank_time = ktime_to_timeval(etime);
>  
>  	DRM_DEBUG_VBL("crtc %u : v 0x%x p(%d,%d)@ %ld.%ld -> %ld.%ld
> [e %d us, %d rep]\n",b