mtd: st_spi_fsm: Add the ability to read from a Serial Flash device

When a read is issued by userspace the MTD framework calls back into
the driver to conduct the actual command issue and data extraction.
Here we provide the routines which do exactly that.

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Write to Flash via the FSM FIFO

When we write data to the FIFO the FSM Controller subsequently writes
that data out to the Serial Flash chip.

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Supply a busy wait for post-write status

When we write data to the Serial Flash chip we'll wait a predetermined
period of time before giving up. During that period of time we poll the
status register until completion.

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Erase partly or as a whole a Serial Flash device

When an erase is requested by userspace the MTD framework calls back
into the driver to conduct the actual command issue. Here we provide the
routines which do exactly that. We can choose to either do an entire chip
erase or by sector.

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Add the ability to read the FSM's status

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Add the ability to write to FSM's status register

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Supply the MX25xxx chip specific configuration call-back

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Supply the S25FLxxx chip specific configuration call-back

This patch allows us to prepare some of the message sequences which will
be required to talk to the  S25FLxxx family of Serial Flash devices. It
also allows us to do some required extra operations after any busy wait
failures.

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Supply the W25Qxxx chip specific configuration call-back

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Move runtime configurable msg sequences into device's struct

Until now the dynamically configurable message sequences for read, write
and enable 32bit addressing have been global. Brian makes a good point
why this should not be the case. If there are ever two FSM's located on
the same platform, we could be potentially introducing a race condition
on "needlessly shared data".

Suggested-by: Brian Norris <computersforpeace@gmail.com>
Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Convert ST SPI FSM (NOR) Flash driver to new DT partitions

The old API expected a "partitions" property provided a phandle to a
separate partitions node, which itself contained yet more nodes each
representing one partition. The new API rids the requirement for the
superfluous intermediary partitions node. This patch provides the
added information required for automatic parsing by the core.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Remove useless consts from function arguments

Reported-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
[Brian: tweaked a bit]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Avoid duplicating MTD core code

Reported-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Correct vendor name spelling issue - missing "M"

Reported-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Allow loop to run at least once before giving up CPU

Reported-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
mtd: st_spi_fsm: Succinctly reorganise .remove()

Reported-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
CPU hotplug: Add lockdep annotations to get/put_online_cpus()

Add lockdep annotations for get/put_online_cpus() and
cpu_hotplug_begin()/cpu_hotplug_end().

Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CPU hotplug: Provide lockless versions of callback registration functions

The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

The deadlock is shown below:

          CPU 0                                         CPU 1
          -----                                         -----

   Acquire cpu_hotplug.lock
   [via get_online_cpus()]

                                              CPU online/offline operation
                                              takes cpu_add_remove_lock
                                              [via cpu_maps_update_begin()]

   Try to acquire
   cpu_add_remove_lock
   [via register_cpu_notifier()]

                                              CPU online/offline operation
                                              tries to acquire cpu_hotplug.lock
                                              [via cpu_hotplug_begin()]

                            *** DEADLOCK! ***

The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.

This can be achieved by writing the callback registration code as follows:

	cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* This doesn't take the cpu_add_remove_lock */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_maps_update_done();  [ or cpu_notifier_register_done(); see below ]

Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.

Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.

Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().

In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Doc/cpu-hotplug: Specify race-free way to register CPU hotplug callbacks

Recommend the usage of the new CPU hotplug callback registration APIs
(__register_cpu_notifier() etc), when subsystems need to also perform
initialization for already online CPUs. Provide examples of correct
and race-free ways of achieving this, and point out the kinds of code
that are error-prone.

Cc: Rob Landley <rob@landley.net>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CPU hotplug, perf: Fix CPU hotplug callback registration

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();

Fix the perf subsystem's hotplug notifier by using this latter form of
callback registration.

Also provide a bare-bones version of perf_cpu_notifier() that doesn't
invoke the notifiers for the already online CPUs. This would be useful
for subsystems that need to perform a different set of initialization
for the already online CPUs, or don't need the initialization altogether.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>