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 at lists.freedesktop.org
Reporter: Peter.Blum at 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.
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