counter: fix privdata alignment

Aligning to the L1 cache does not guarantee the same alignment as
kmallocing an object [1]. Furthermore, in some platforms, that
alignment is not sufficient for DMA safety (in case someone wants
to have a DMA safe buffer in privdata) [2].

Sometime ago, we had the same fixes in IIO.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/devres.c#n35
[2]: https://lore.kernel.org/linux-iio/20220508175712.647246-2-jic23@kernel.org/

Fixes: c18e2760308e ("counter: Provide alternative counter registration functions")
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240209-counter-align-fix-v2-1-5777ea0a2722@analog.com
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>

counter: Move symbols into COUNTER namespace

Counter subsystem symbols are only relevant to counter drivers. A
COUNTER namespace is created to control the availability of these
symbols to modules that import this namespace explicitly.

Cc: Patrick Havelange <patrick.havelange@essensium.com>
Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Cc: Oleksij Rempel <linux@rempel-privat.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Kamel Bouhara <kamel.bouhara@bootlin.com>
Cc: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Acked-by: David Lechner <david@lechnology.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20220815220321.74161-1-william.gray@linaro.org/
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/8a756df96c24946547a7ece5caa5f654809c5e7f.1664318353.git.william.gray@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: Set counter device name

Naming the counter device provides a convenient way to identify it in
devres_log events and similar situations. This patch names the counter
device by combining the prefix "counter" with the counter device's
unique ID.

Link: https://lore.kernel.org/r/20220204084551.16397-1-vilhelm.gray@gmail.com
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/87cc8eb4c84f49f89290577dc9231b2e4d7d3e8c.1647373009.git.vilhelm.gray@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: fix an IS_ERR() vs NULL bug

There are 8 callers for devm_counter_alloc() and they all check for NULL
instead of error pointers. I think NULL is the better thing to return
for allocation functions so update counter_alloc() and devm_counter_alloc()
to return NULL instead of error pointers.

Fixes: c18e2760308e ("counter: Provide alternative counter registration functions")
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20220111173243.GA2192@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: remove old and now unused registration API

Usage of counter_register() yields issues in device lifetime tracking. All
drivers were converted to the new API, so the old one can go away.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211230150300.72196-24-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: Provide alternative counter registration functions

The current implementation gets device lifetime tracking wrong. The
problem is that allocation of struct counter_device is controlled by the
individual drivers but this structure contains a struct device that
might have to live longer than a driver is bound. As a result a command
sequence like:

{ sleep 5; echo bang; } > /dev/counter0 &
sleep 1;
echo 40000000.timer:counter > /sys/bus/platform/drivers/stm32-timer-counter/unbind

can keep a reference to the struct device and unbinding results in
freeing the memory occupied by this device resulting in an oops.

This commit provides two new functions (plus some helpers):
- counter_alloc() to allocate a struct counter_device that is
automatically freed once the embedded struct device is released
- counter_add() to register such a device.

Note that this commit doesn't fix any issues, all drivers have to be
converted to these new functions to correct the lifetime problems.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211230150300.72196-14-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: Provide a wrapper to access device private data

For now this just wraps accessing struct counter_device::priv. However
this is about to change and converting drivers to this helper
individually makes fixing device lifetime issues result in easier to
review patches.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211230150300.72196-5-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: Use container_of instead of drvdata to track counter_device

The counter core uses drvdata to find a struct counter_device from a
struct device. However as the device is a member of struct counter_device,
the lookup can be done faster (and a bit type safe) using container_of.

There are no other users of drvdata, so the call to dev_set_drvdata can
go away, too.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211230150300.72196-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

counter: Add character device interface

This patch introduces a character device interface for the Counter
subsystem. Device data is exposed through standard character device read
operations. Device data is gathered when a Counter event is pushed by
the respective Counter device driver. Configuration is handled via ioctl
operations on the respective Counter character device node.

Cc: David Lechner <david@lechnology.com>
Cc: Gwendal Grignou <gwendal@chromium.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/b8b8c64b4065aedff43699ad1f0e2f8d1419c15b.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

counter: Update counter.h comments to reflect sysfs internalization

The Counter subsystem architecture and driver implementations have
changed in order to handle Counter sysfs interactions in a more
consistent way. This patch updates the Generic Counter interface
header file comments to reflect the changes.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/19da8ae0c05381b0967c8a334b67f86b814eb880.1630031207.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

counter: Internalize sysfs interface code

This is a reimplementation of the Generic Counter driver interface.
There are no modifications to the Counter subsystem userspace interface,
so existing userspace applications should continue to run seamlessly.

The purpose of this patch is to internalize the sysfs interface code
among the various counter drivers into a shared module. Counter drivers
pass and take data natively (i.e. u8, u64, etc.) and the shared counter
module handles the translation between the sysfs interface and the
device drivers. This guarantees a standard userspace interface for all
counter drivers, and helps generalize the Generic Counter driver ABI in
order to support the Generic Counter chrdev interface (introduced in a
subsequent patch) without significant changes to the existing counter
drivers.

Note, Counter device registration is the same as before: drivers
populate a struct counter_device with components and callbacks, then
pass the structure to the devm_counter_register function. However,
what's different now is how the Counter subsystem code handles this
registration internally.

Whereas before callbacks would interact directly with sysfs data, this
interaction is now abstracted and instead callbacks interact with native
C data types. The counter_comp structure forms the basis for Counter
extensions.

The counter-sysfs.c file contains the code to parse through the
counter_device structure and register the requested components and
extensions. Attributes are created and populated based on type, with
respective translation functions to handle the mapping between sysfs and
the counter driver callbacks.

The translation performed for each attribute is straightforward: the
attribute type and data is parsed from the counter_attribute structure,
the respective counter driver read/write callback is called, and sysfs
I/O is handled before or after the driver read/write function is called.

Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Cc: Patrick Havelange <patrick.havelange@essensium.com>
Cc: Kamel Bouhara <kamel.bouhara@bootlin.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Syed Nayyar Waris <syednwaris@gmail.com>
Reviewed-by: David Lechner <david@lechnology.com>
Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> # for stm32
Link: https://lore.kernel.org/r/c68b4a1ffb195c1a2f65e8dd5ad7b7c14e79c6ef.1630031207.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>