clk: baikal-t1: Move reset-controls code into a dedicated module

Before adding the directly controlled resets support it's reasonable to
move the existing resets control functionality into a dedicated object for
the sake of the CCU dividers clock driver simplification. After the new
functionality was added clk-ccu-div.c would have got to a mixture of the
weakly dependent clocks and resets methods. Splitting the methods up into
the two objects will make the code easier to read and maintain. It shall
also improve the code scalability (though hopefully we won't need this
part that much in the future).

The reset control functionality is now implemented in the framework of a
single unit since splitting it up doesn't make much sense due to
relatively simple reset operations. The ccu-rst.c has been designed to be
looking like ccu-div.c or ccu-pll.c with two globally available methods
for the sake of the code unification and better code readability.

This commit doesn't provide any change in the CCU reset implementation
semantics. As before the driver will support the trigger-like CCU resets
only, which are responsible for the AXI-bus, APB-bus and SATA-ref blocks
reset. The assert/de-assert-capable reset controls support will be added
in the next commit.

Note the CCU Clock dividers and resets functionality split up was possible
due to not having any side-effects (at least we didn't found ones) of the
regmap-based concurrent access of the common CCU dividers/reset CSRs.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20220929225402.9696-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

clk: baikal-t1: Add SATA internal ref clock buffer

It turns out the internal SATA reference clock signal will stay
unavailable for the SATA interface consumer until the buffer on it's way
is ungated. So aside with having the actual clock divider enabled we need
to ungate a buffer placed on the signal way to the SATA controller (most
likely some rudiment from the initial SoC release). Seeing the switch flag
is placed in the same register as the SATA-ref clock divider at a
non-standard ffset, let's implement it as a separate clock controller with
the set-rate propagation to the parental clock divider wrapper. As such
we'll be able to disable/enable and still change the original clock source
rate.

Fixes: 353afa3a8d2e ("clk: Add Baikal-T1 CCU Dividers driver")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20220929225402.9696-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

clk: baikal-t1: Add shared xGMAC ref/ptp clocks internal parent

Baikal-T1 CCU reference manual says that both xGMAC reference and xGMAC
PTP clocks are generated by two different wrappers with the same constant
divider thus each producing a 156.25 MHz signal. But for some reason both
of these clock sources are gated by a single switch-flag in the CCU
registers space - CCU_SYS_XGMAC_BASE.BIT(0). In order to make the clocks
handled independently we need to define a shared parental gate so the base
clock signal would be switched off only if both of the child-clocks are
disabled.

Note the ID is intentionally set to -2 since we are going to add a one
more internal clock identifier in the next commit.

Fixes: 353afa3a8d2e ("clk: Add Baikal-T1 CCU Dividers driver")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20220929225402.9696-4-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

clk: baikal-t1: remove redundant assignment to variable 'divider'

The variable divider is being initialized with a value that is never read
and it is being updated later with a new value. The initialization is
redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20200602172435.70282-1-colin.king@canonical.com
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

clk: Add Baikal-T1 CCU Dividers driver

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
Link: https://lore.kernel.org/r/20200526222056.18072-5-Sergey.Semin@baikalelectronics.ru
[sboyd@kernel.org: Drop return from void function, silence sparse
warnings about initializing structs with NULL vs. integer]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>