net: mdio: realtek-rtl9300: provide generic command runner

The current bus read/write commands for C22/C45 are RTL930x specific.
Avoid to duplicate those 200 lines of code for the RTL838x, RTL839x and
RTL931x targets. Instead provide a generic command runner that is SoC
independent. The implementation works as follows:

The runner will take a prepared list of the four MDIO registers. It will
feed the data into the registers. This generic write to all registers
(or to say "a little bit too much") is no issue. The hardware looks at
the to be executed command and will only take the pieces of data that
are really required. No side effects have been observed on any of the
four SoCs during the time this mechanism exists in downstream OpenWrt.

The last fed register is the C22/command register. This will be enriched
with the proper command flags from the caller. The hardware issues the
command and the runner will wait for its finalization.

Besides from feeding all registers the runner emulates the behaviour of
the old code as best as possible

- check defensively for a running command in advance
- Before this commit the driver had different MMIO timeout values.
  1000s for command preparation, 100us after writes and 1000us after
  reads. The new version uses a consistent 1000us timeout for all
  of these.
- return -ENXIO in case of hardware failure (fail bit)

As a first consumer of this runner convert the write_c45() function.
This is realized in a multi stage approach

- a generic otto_emdio_write_c45() will be called by the bus
- this will forward the request to the device specific writer. In this
  case otto_emdio_9300_write_c45().
- There the command data is filled in and the additional helper
  otto_emdio_write_cmd() will be called
- That adds the write flag and issues the generic command runner.

With all the above mentioned in place, there is not much left to do in
otto_emdio_9300_write_c45(). It just fills the register fields and
calls the write helper with the right command bits.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20260527163449.1294961-2-markus.stockhausen@gmx.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions