On Wed, May 27, 2015 at 04:17:05PM +0900, Michel Dänzer wrote:
On 26.05.2015 20:48, Daniel Vetter wrote:
On Tue, May 26, 2015 at 05:53:38PM +0900, Michel Dänzer wrote:
From: Michel Dänzer michel.daenzer@amd.com
dev->max_vblank_count contains the largest value that can be represented by the hardware counter. When the hardware counter wraps around, we have to add that value + 1 to get the same value as if the hardware counter didn't wrap around.
Signed-off-by: Michel Dänzer michel.daenzer@amd.com
Well there's two users of this really, one wants the max (this one here) and the other a mask.
Well, this one has been around much longer. :) Looks like drm_vblank_on added a (probably valid, see below) assumption without updating the field name to reflect that.
Yeah, might be clearer to open-code the (slower) divide just for clarity. Anyway applied this patch to drm-misc.
And all the drivers use it as a mask.
How so? They just assign the value, which happens to work for both meanings above in all cases.
Yeah I had the usual confusion about where exactly we start counting here ;-) I was thinking of num_vblank_counts_before_wrap vs. mask. -Daniel