ipmi: fix potential deadlock on &kcs_bmc->lock

As kcs_bmc_handle_event() is executed inside both a timer and a hardirq,
it should disable irq before lock acquisition otherwise deadlock could
happen if the timmer is preemtped by the irq.

Possible deadlock scenario:
aspeed_kcs_check_obe() (timer)
-> kcs_bmc_handle_event()
-> spin_lock(&kcs_bmc->lock)
<irq interruption>
-> aspeed_kcs_irq()
-> kcs_bmc_handle_event()
-> spin_lock(&kcs_bmc->lock) (deadlock here)

This flaw was found using an experimental static analysis tool we are
developing for irq-related deadlock.

The tentative patch fix the potential deadlock by spin_lock_irqsave()

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Message-Id: <20230627152449.36093-1-dg573847474@gmail.com>
Signed-off-by: Corey Minyard <minyard@acm.org>

ipmi: kcs_bmc: Enable IBF on open

This way devices don't get delivered IRQs when no-one is interested.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Message-Id: <20210608104757.582199-11-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

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: Decouple the IPMI chardev from the core

Now that we have untangled the data-structures, split the userspace
interface out into its own module. Userspace interfaces and drivers are
registered to the KCS BMC core to support arbitrary binding of either.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Message-Id: <20210608104757.582199-9-andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
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: Rename {read,write}_{status,data}() functions

Rename the functions in preparation for separating the IPMI chardev out
from the KCS BMC core.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-4-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>

treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

ipmi: kcs_bmc: handle devm_kasprintf() failure case

devm_kasprintf() may return NULL if internal allocation failed so this
assignment is not safe. Moved the error exit path and added the !NULL
which then allows the devres manager to take care of cleanup.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: cd2315d471f4 ("ipmi: kcs_bmc: don't change device name")
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Haiyue Wang <haiyue.wang@linux.intel.com>

ipmi: kcs_bmc: don't change device name

kcs_bmc_alloc(...) calls dev_set_name(...) which is incorrect as most
bus driver frameworks, platform_driver in particular, assume that they
are able to set the device name themselves.

Signed-off-by: Benjamin Fair <benjaminfair@google.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

ipmi: kcs_bmc: fix IRQ exception if the channel is not open

When kcs_bmc_handle_event calls kcs_force_abort function to handle the
not open (no user running) KCS channel transaction, the returned status
value -ENODEV causes the low level IRQ handler indicating that the irq
was not for him by returning IRQ_NONE. After some time, this IRQ will
be treated to be spurious one, and the exception dump happens.

irq 30: nobody cared (try booting with the "irqpoll" option)
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.10.15-npcm750 #1
Hardware name: NPCMX50 Chip family
[<c010b264>] (unwind_backtrace) from [<c0106930>] (show_stack+0x20/0x24)
[<c0106930>] (show_stack) from [<c03dad38>] (dump_stack+0x8c/0xa0)
[<c03dad38>] (dump_stack) from [<c0168810>] (__report_bad_irq+0x3c/0xdc)
[<c0168810>] (__report_bad_irq) from [<c0168c34>] (note_interrupt+0x29c/0x2ec)
[<c0168c34>] (note_interrupt) from [<c0165c80>] (handle_irq_event_percpu+0x5c/0x68)
[<c0165c80>] (handle_irq_event_percpu) from [<c0165cd4>] (handle_irq_event+0x48/0x6c)
[<c0165cd4>] (handle_irq_event) from [<c0169664>] (handle_fasteoi_irq+0xc8/0x198)
[<c0169664>] (handle_fasteoi_irq) from [<c016529c>] (__handle_domain_irq+0x90/0xe8)
[<c016529c>] (__handle_domain_irq) from [<c01014bc>] (gic_handle_irq+0x58/0x9c)
[<c01014bc>] (gic_handle_irq) from [<c010752c>] (__irq_svc+0x6c/0x90)
Exception stack(0xc0a01de8 to 0xc0a01e30)
1de0: 00002080 c0a6fbc0 00000000 00000000 00000000 c096d294
1e00: 00000000 00000001 dc406400 f03ff100 00000082 c0a01e94 c0a6fbc0 c0a01e38
1e20: 00200102 c01015bc 60000113 ffffffff
[<c010752c>] (__irq_svc) from [<c01015bc>] (__do_softirq+0xbc/0x358)
[<c01015bc>] (__do_softirq) from [<c011c798>] (irq_exit+0xb8/0xec)
[<c011c798>] (irq_exit) from [<c01652a0>] (__handle_domain_irq+0x94/0xe8)
[<c01652a0>] (__handle_domain_irq) from [<c01014bc>] (gic_handle_irq+0x58/0x9c)
[<c01014bc>] (gic_handle_irq) from [<c010752c>] (__irq_svc+0x6c/0x90)
Exception stack(0xc0a01ef8 to 0xc0a01f40)
1ee0: 00000000 000003ae
1f00: dcc0f338 c0111060 c0a00000 c0a0cc44 c0a0cbe4 c0a1c22b c07bc218 00000001
1f20: dcffca40 c0a01f54 c0a01f58 c0a01f48 c0103524 c0103528 60000013 ffffffff
[<c010752c>] (__irq_svc) from [<c0103528>] (arch_cpu_idle+0x48/0x4c)
[<c0103528>] (arch_cpu_idle) from [<c0681390>] (default_idle_call+0x30/0x3c)
[<c0681390>] (default_idle_call) from [<c0156f24>] (do_idle+0xc8/0x134)
[<c0156f24>] (do_idle) from [<c015722c>] (cpu_startup_entry+0x28/0x2c)
[<c015722c>] (cpu_startup_entry) from [<c067ad74>] (rest_init+0x84/0x88)
[<c067ad74>] (rest_init) from [<c0900d44>] (start_kernel+0x388/0x394)
[<c0900d44>] (start_kernel) from [<0000807c>] (0x807c)
handlers:
[<c041c5dc>] npcm7xx_kcs_irq
Disabling IRQ #30

It needs to change the returned status from -ENODEV to 0. The -ENODEV
was originally used to tell the low level IRQ handler that no user was
running, but not consider the IRQ handling desgin.

And multiple KCS channels share one IRQ handler, it needs to check the
IBF flag before doing force abort. If the IBF is set, after handling,
return 0 to low level IRQ handler to indicate that the IRQ is handled.

Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
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: kcs_bmc: mark expected switch fall-through in kcs_bmc_handle_data

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 1465255 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Cc: 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>