On 12/3/24 3:07 PM, Dmitry Baryshkov wrote: > On Tue, Dec 03, 2024 at 04:13:22PM +0800, Xiangxu Yin wrote: >> >> >> On 11/29/2024 9:53 PM, Dmitry Baryshkov wrote: >>> On Fri, 29 Nov 2024 at 09:59, Xiangxu Yin <quic_xiang...@quicinc.com> wrote: >>>> >>>> Add a mechanism to retry Link Training 2 by lowering the pattern level >>>> when the link training #2 first attempt fails. This approach enhances >>>> compatibility, particularly addressing issues caused by certain hub >>>> configurations. >>> >>> Please reference corresponding part of the standard, describing this >>> lowering. >>> >> Per DisplayPort 1.4a specification Section 3.5.1.2 and Table 3-10, while the >> standard doesn't explicitly define a TPS downgrade mechanism, it does >> specify: > > Anything in DP 2.1? > >> - All devices shall support TPS1 and TPS2 >> - HDR2-capable devices shall support TPS3 >> - HDR3-capable devices shall support TPS4 >> While these capabilities are explicitly defined DPCD for sink devices, >> source device capabilities are less strictly defined, with the minimum >> requirement being support for TPS1 and TPS2. >> In QCS615 DP phy is only supporting to HBR2, we observed a critical >> interoperability scenario with a DP->HDMI bridge. When link training at TPS4 >> consistently failed, downgrading to the next lower training pattern >> successfully established the link and display output successfully. > > Any other driver doing such TPS lowering? Or maybe we should be > selecting TPS3 for HBR2-only devices?
Bump, this patch looks interesting and I'd like to see it revisited if it's correct Konrad
