On Fri, Oct 23, 2020 at 03:14:20PM +0000, Simon Ser wrote:
On Thursday, October 22, 2020 12:14 PM, Ville Syrjälä ville.syrjala@linux.intel.com wrote:
On Wed, Oct 21, 2020 at 08:13:43PM -0700, Randy Dunlap wrote:
Hi, With linux-next 20201021, when booting up, I am seeing this: [ 0.560896] UBSAN: signed-integer-overflow in ../drivers/gpu/drm/drm_modes.c:765:20 [ 0.560903] 2376000 * 1000 cannot be represented in type 'int'
Dang. Didn't realize these new crazy >8k modes have dotclocks reaching almost 6 GHz, which would overflow even u32. I guess we'll switch to 64bit maths. Now I wonder how many other places can hit this overflow in practice...
Can you provide an example of a full crazy >8k mode?
These are two extreme cases: /* 216 - 10240x4320@100Hz 64:27 */ { DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 12432, 12608, 13200, 0, 4320, 4336, 4356, 4500, 0, DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC), .picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, }, /* 217 - 10240x4320@120Hz 64:27 */ { DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 10528, 10704, 11000, 0, 4320, 4336, 4356, 4500, 0, DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC), .picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, }
I'm trying to get a fix for my user-space [1], and I'm wondering if int32_t is enough after dividing by mode->htotal.
CC Pekka, just FYI (I think Weston has similar code).
What's with those 1000000LL constants? Are you storing clock in Hz units?