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All > > hardware IP blocks have their registers mapped here, and the Device > > Configuration block makes no exception. > > > > However, there exists a secondary range of the address space named DCSR > > ("Debug Control and Status Registers") which, like CCSR, also holds > > registers of hardware IP blocks, except the DCSR contents is hidden in > > all public reference manuals. > > > > The intention of the CCSR/DCSR split, to the best of my knowledge, was > > to place the functionality that is too low level for normal use, and > > which is necessary only for debug, in a completely separate address > > space which can be hidden. > > > > A use case has appeared where networking SerDes lanes need to be > > reconfigured at runtime for a different protocol (example: 10GBase-R to > > SGMII), and the architecture of the SoCs does not normally permit that. > > The Reset Configuration Word (RCW) is a data structure read by the SoC > > preboot loader (PBL) which contains stuff like pinmuxing and SerDes > > protocol mapping for each lane. > > > > The RCW that the PBL has loaded is visible in the DCFG block's normal > > status registers (from CCSR), as read only. Turns out, the RCW is also > > mapped in the DCFG's shadow register map (in DCSR), in a write-only > > form. Writing to the RCW registers from the DCFG's DCSR space to change > > what the PBL has loaded is called "RCW override". > > > > It has been validated that the RCW override procedure is necessary to > > reconfigure the networking data path when a SerDes lane performs a major > > protocol change. It changes some internal muxes which connect the PCS to > > either the 10G MAC or to the 1G MAC. > > > > Defining the DCSR area of the DCFG as a secondary 'reg' array element > > allows operating systems to perform RCW overrides. Since it is > > introduced late in the binding's lifetime, it is optional. It can be > > identified by name, but also by index (first 'reg' is CCSR). > > > > Note that while all SoCs should have a DCFG register block in DCSR, we > > only need to expose it for the SoCs where the RCW override procedure is > > known to be needed and has been validated. > > > > Signed-off-by: Vladimir Oltean > > --- > > Cc: Conor Dooley > > Where did this email come from btw? get_maintainer.pl result should have > +dt in it. Historical data. I am keeping all sorts of commands (here git send-email) in *.txt files and that's where I got the stale email addresses from. Krzysztof's is also bouncing. Will fix for v2. > Reviewed-by: Conor Dooley > pw-bot: not-applicable Thanks for the review!