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Commit 25e1a798 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Dave Airlie
Browse files

drm: vblank: remove drm_timestamp_monotonic parameter 



There is a risk of overflowing vblank timestamps in 2038 or 2106 if
someone sets the drm_timestamp_monotonic module parameter to zero.

I found no indication of anyone ever setting the parameter, or
complaining about the default being wrong, after it was introduced
as a way to handle backwards-compatibility with linux prior to
c61eef72 ("drm: add support for monotonic vblank timestamps"),
so it's probably safer to just remove the parameter completely
and only allowing the default behavior.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarDaniel Stone <daniels@collabora.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 67680d3c

drivers/gpu/drm/drm_internal.h

+0 −1
Original line number Diff line number Diff line
@@ -55,7 +55,6 @@ int drm_clients_info(struct seq_file *m, void* data); 
int drm_gem_name_info(struct seq_file *m, void *data);



/* drm_vblank.c */

extern unsigned int drm_timestamp_monotonic;

void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe);

void drm_vblank_cleanup(struct drm_device *dev);

drivers/gpu/drm/drm_ioctl.c

+1 −1
Original line number Diff line number Diff line
@@ -235,7 +235,7 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_ 
	/* Only some caps make sense with UMS/render-only drivers. */

	switch (req->capability) {

	case DRM_CAP_TIMESTAMP_MONOTONIC:

		req->value = drm_timestamp_monotonic;

		req->value = 1;

		return 0;

	case DRM_CAP_PRIME:

		req->value |= dev->driver->prime_fd_to_handle ? DRM_PRIME_CAP_IMPORT : 0;

drivers/gpu/drm/drm_vblank.c

+6 −23
Original line number Diff line number Diff line
@@ -82,20 +82,12 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, 


static unsigned int drm_timestamp_precision = 20;  /* Default to 20 usecs. */



/*

 * Default to use monotonic timestamps for wait-for-vblank and page-flip

 * complete events.

 */

unsigned int drm_timestamp_monotonic = 1;



static int drm_vblank_offdelay = 5000;    /* Default to 5000 msecs. */



module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);

module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);

module_param_named(timestamp_monotonic, drm_timestamp_monotonic, int, 0600);

MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs] (0: never disable, <0: disable immediately)");

MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");

MODULE_PARM_DESC(timestamp_monotonic, "Use monotonic timestamps");



static void store_vblank(struct drm_device *dev, unsigned int pipe,

			 u32 vblank_count_inc,
@@ -672,9 +664,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, 
	delta_ns = div_s64(1000000LL * (vpos * mode->crtc_htotal + hpos),

			   mode->crtc_clock);



	if (!drm_timestamp_monotonic)

		etime = ktime_mono_to_real(etime);



	/* save this only for debugging purposes */

	ts_etime = ktime_to_timespec64(etime);

	ts_vblank_time = ktime_to_timespec64(*vblank_time);
@@ -694,11 +683,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, 
}

EXPORT_SYMBOL(drm_calc_vbltimestamp_from_scanoutpos);



static ktime_t get_drm_timestamp(void)

{

	return drm_timestamp_monotonic ? ktime_get() : ktime_get_real();

}



/**

 * drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent

 *                             vblank interval
@@ -738,7 +722,7 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, 
	 * Return current monotonic/gettimeofday timestamp as best estimate.

	 */

	if (!ret)

		*tvblank = get_drm_timestamp();

		*tvblank = ktime_get();



	return ret;

}
@@ -811,8 +795,8 @@ static void send_vblank_event(struct drm_device *dev, 
	e->event.sequence = seq;

	/*

	 * e->event is a user space structure, with hardcoded unsigned

	 * 32-bit seconds/microseconds. This will overflow in 2106 for

	 * drm_timestamp_monotonic==0, but not with drm_timestamp_monotonic==1

	 * 32-bit seconds/microseconds. This is safe as we always use

	 * monotonic timestamps since linux-4.15

	 */

	e->event.tv_sec = tv.tv_sec;

	e->event.tv_usec = tv.tv_nsec / 1000;
@@ -899,7 +883,7 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc, 
	} else {

		seq = 0;



		now = get_drm_timestamp();

		now = ktime_get();

	}

	e->pipe = pipe;

	e->event.crtc_id = crtc->base.id;
@@ -1408,9 +1392,8 @@ static void drm_wait_vblank_reply(struct drm_device *dev, unsigned int pipe, 


	/*

	 * drm_wait_vblank_reply is a UAPI structure that uses 'long'

	 * to store the seconds. This will overflow in y2038 on 32-bit

	 * architectures with drm_timestamp_monotonic==0, but not with

	 * drm_timestamp_monotonic==1 (the default).

	 * to store the seconds. This is safe as we always use monotonic

	 * timestamps since linux-4.15.

	 */

	reply->sequence = drm_vblank_count_and_time(dev, pipe, &now);

	ts = ktime_to_timespec64(now);