Re: [PATCH v3 4/4] clk: Add Baikal-T1 CCU Dividers driver

[Stephen Boyd <sboyd@kernel.org>]

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@baikalelectronics.ru>
> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: linux-mips@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> 
> ---

Applied to clk-next