https://bugs.freedesktop.org/show_bug.cgi?id=91789

Bug ID: 91789 Summary: MST (multi stream) with Asus PQ321 drm_dp_calc_pbn_mode() fails Product: DRI Version: unspecified Hardware: x86 (IA32) OS: Linux (All) Status: NEW Severity: normal Priority: medium Component: General Assignee: dri-devel@lists.freedesktop.org Reporter: Peter.Blum@lxco.com

If a Asus monitor PQ321 is used in MST mode it gets no signal. This is because the function drm_dp_calc_pbn_mode() in drm_dp_mst_topology.c returns a bad pixel bandwith number for the mode

Modeline 131:"1920x2160" 60 297000 1920 2008 2052 2200 2160 2168 2178 2250 0x48 0x5

The function return 8 and not the correct value of 1063.

Using simple u32 arithmetic in drm_dp_calc_pbn_mode() the monitor works fine.

I'm not sure if unsigned 32 bit would overflow in some cases.