ipmi: kcs_bmc: Allow clients to control KCS IRQ state

Add a mechanism for controlling whether the client associated with a
KCS device will receive Input Buffer Full (IBF) and Output Buffer Empty
(OBE) events. This enables an abstract implementation of poll() for KCS
devices.

A wart in the implementation is that the ASPEED KCS devices don't
support an OBE interrupt for the BMC. Instead we pretend it has one by
polling the status register waiting for the Output Buffer Full (OBF) bit
to clear, and generating an event when OBE is observed.

Cc: CS20 KWLiu <KWLIU@nuvoton.com>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-10-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: Strip private client data from struct kcs_bmc

Move all client-private data out of `struct kcs_bmc` into the KCS client
implementation.

With this change the KCS BMC core code now only concerns itself with
abstract `struct kcs_bmc` and `struct kcs_bmc_client` types, achieving
expected separation of concerns. Further, the change clears the path for
implementation of alternative userspace interfaces.

The chardev data-structures are rearranged in the same manner applied to
the KCS device driver data-structures in an earlier patch - `struct
kcs_bmc_client` is embedded in the client's private data and we exploit
container_of() to translate as required.

Finally, now that it is free of client data, `struct kcs_bmc` is renamed
to `struct kcs_bmc_device` to contrast `struct kcs_bmc_client`.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-8-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: Split headers into device and client

Strengthen the distinction between code that abstracts the
implementation of the KCS behaviours (device drivers) and code that
exploits KCS behaviours (clients). Neither needs to know about the APIs
required by the other, so provide separate headers.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Message-Id: <20210608104757.582199-7-andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: Turn the driver data-structures inside-out

Make the KCS device drivers responsible for allocating their own memory.

Until now the private data for the device driver was allocated internal
to the private data for the chardev interface. This coupling required
the slightly awkward API of passing through the struct size for the
driver private data to the chardev constructor, and then retrieving a
pointer to the driver private data from the allocated chardev memory.

In addition to being awkward, the arrangement prevents the
implementation of alternative userspace interfaces as the device driver
private data is not independent.

Peel a layer off the onion and turn the data-structures inside out by
exploiting container_of() and embedding `struct kcs_device` in the
driver private data.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-6-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: Split out kcs_bmc_cdev_ipmi

Take steps towards defining a coherent API to separate the KCS device
drivers from the userspace interface. Decreasing the coupling will
improve the separation of concerns and enable the introduction of
alternative userspace interfaces.

For now, simply split the chardev logic out to a separate file. The code
continues to build into the same module.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-5-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: Make status update atomic

Enable more efficient implementation of read-modify-write sequences.
Both device drivers for the KCS BMC stack use regmaps. The new callback
allows us to exploit regmap_update_bits().

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-3-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: coding-style fixes and use new poll type

Many for coding-style fixes, and update the poll API with the new
type '__poll_t', this is new commit from linux-4.16-rc1.

Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: add a KCS IPMI BMC driver

Provides a device driver for the KCS (Keyboard Controller Style)
IPMI interface which meets the requirement of the BMC (Baseboard
Management Controllers) side for handling the IPMI request from
host system software.

Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
[Removed the selectability of IPMI_KCS_BMC, as it doesn't do much
good to have it by itself.]
Signed-off-by: Corey Minyard <cminyard@mvista.com>