Quoting Serge Semin (2020-05-26 15:20:56) > Nearly each Baikal-T1 IP-core is supposed to have a clock source > of particular frequency. But since there are greater than five > IP-blocks embedded into the SoC, the CCU PLLs can't fulfill all the > needs. Baikal-T1 CCU provides a set of fixed and configurable clock > dividers in order to generate a necessary signal for each chip > sub-block. > > This driver creates the of-based hardware clocks for each divider > available in Baikal-T1 CCU. The same way as for PLLs we split the > functionality up into the clocks operations (gate, ungate, set rate, > etc) and hardware clocks declaration/registration procedures. > > In accordance with the CCU documentation all its dividers are distributed > into two CCU sub-blocks: AXI-bus and system devices reference clocks. > The former sub-block is used to supply the clocks for AXI-bus interfaces > (AXI clock domains) and the later one provides the SoC IP-cores reference > clocks. Each sub-block is represented by a dedicated DT node, so they > have different compatible strings to distinguish one from another. > > For some reason CCU provides the dividers of different types. Some > dividers can be gateable some can't, some are fixed while the others > are variable, some have special divider' limitations, some've got a > non-standard register layout and so on. In order to cover all of these > cases the hardware clocks driver is designed with an info-descriptor > pattern. So there are special static descriptors declared for the > dividers of each type with additional flags describing the block > peculiarity. These descriptors are then used to create hardware clocks > with proper operations. > > Some CCU dividers provide a way to reset a domain they generate > a clock for. So the CCU AXI-bus and CCU system devices clock > drivers also perform the reset controller registration. > > Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> > Cc: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > Cc: linux-mips@xxxxxxxxxxxxxxx > Cc: devicetree@xxxxxxxxxxxxxxx > > --- Applied to clk-next
