[5/8] iio/counter: add FlexTimer Module Quadrature decoder counter driver

Commit Message

Patrick Havelange Feb. 18, 2019, 2:03 p.m. UTC

This driver exposes the counter for the quadrature decoder of the
FlexTimer Module, present in the LS1021A soc.

Signed-off-by: Patrick Havelange <[e-mail]>
Reviewed-by: Esben Haabendal <[e-mail]>
---
 drivers/iio/counter/Kconfig       |  10 +
 drivers/iio/counter/Makefile      |   1 +
 drivers/iio/counter/ftm-quaddec.c | 294 ++++++++++++++++++++++++++++++
 3 files changed, 305 insertions(+)
 create mode 100644 drivers/iio/counter/ftm-quaddec.c

Comments

Jonathan Cameron Feb. 20, 2019, 4:41 p.m. UTC | #1

On Mon, 18 Feb 2019 15:03:18 +0100
Patrick Havelange <[e-mail]> wrote:

> This driver exposes the counter for the quadrature decoder of the
> FlexTimer Module, present in the LS1021A soc.
> 
> Signed-off-by: Patrick Havelange <[e-mail]>
> Reviewed-by: Esben Haabendal <[e-mail]>
Given you cc'd William, I'm guessing you know about the counter
subsystem effort.  I would really rather not take any drivers
into IIO if we have any hope of getting that upstreamed soon
(which I personally think we do and should!).  The reason is
we end up having to maintain old ABI just because someone might be using
it and it makes the drivers very messy.

I'll review as is though as may be there are some elements that will
cross over.

Comments inline.  William: Looks like a straight forward conversion if
it makes sense to get this lined up as part of your initial submission?
You have quite a few drivers so I wouldn't have said it needs to be there
at the start, but good to have it soon after.

Jonathan

> ---
>  drivers/iio/counter/Kconfig       |  10 +
>  drivers/iio/counter/Makefile      |   1 +
>  drivers/iio/counter/ftm-quaddec.c | 294 ++++++++++++++++++++++++++++++
>  3 files changed, 305 insertions(+)
>  create mode 100644 drivers/iio/counter/ftm-quaddec.c
> 
> diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
> index bf1e559ad7cd..4641cb2e752a 100644
> --- a/drivers/iio/counter/Kconfig
> +++ b/drivers/iio/counter/Kconfig
> @@ -31,4 +31,14 @@ config STM32_LPTIMER_CNT
>  
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called stm32-lptimer-cnt.
> +
> +config FTM_QUADDEC
> +	tristate "Flex Timer Module Quadrature decoder driver"
> +	help
> +	  Select this option to enable the Flex Timer Quadrature decoder
> +	  driver.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ftm-quaddec.
> +
>  endmenu
> diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
> index 1b9a896eb488..757c1f4196af 100644
> --- a/drivers/iio/counter/Makefile
> +++ b/drivers/iio/counter/Makefile
> @@ -6,3 +6,4 @@
>  
>  obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
>  obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
> +obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
> diff --git a/drivers/iio/counter/ftm-quaddec.c b/drivers/iio/counter/ftm-quaddec.c
> new file mode 100644
> index 000000000000..ca7e55a9ab3f
> --- /dev/null
> +++ b/drivers/iio/counter/ftm-quaddec.c
> @@ -0,0 +1,294 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Flex Timer Module Quadrature decoder
> + *
> + * This module implements a driver for decoding the FTM quadrature
> + * of ex. a LS1021A
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/workqueue.h>
Tidy these up. Not all are used.
> +#include <linux/swait.h>
> +#include <linux/sched.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +#include <linux/mutex.h>
> +#include <linux/fsl/ftm.h>
> +
> +struct ftm_quaddec {
> +	struct platform_device *pdev;
> +	void __iomem *ftm_base;
> +	bool big_endian;

I'm curious. What is the benefit of running in big endian mode?

> +	struct mutex ftm_quaddec_mutex;
> +};
> +
> +#define HASFLAGS(flag, bits) ((flag & bits) ? 1 : 0)
Not used.


> +
> +#define DEFAULT_POLL_INTERVAL    100 /* in msec */
> +
> +static void ftm_read(struct ftm_quaddec *ftm, uint32_t offset, uint32_t *data)
> +{
> +	if (ftm->big_endian)
> +		*data = ioread32be(ftm->ftm_base + offset);
> +	else
> +		*data = ioread32(ftm->ftm_base + offset);
> +}
> +
> +static void ftm_write(struct ftm_quaddec *ftm, uint32_t offset, uint32_t data)
> +{
> +	if (ftm->big_endian)
> +		iowrite32be(data, ftm->ftm_base + offset);
> +	else
> +		iowrite32(data, ftm->ftm_base + offset);
> +}
> +
> +/* take mutex

Tidy this comment up.  I  would have said the flow as fairly
obvious and the only thing needed here is to document that
the mutex must be held?

> + * call ftm_clear_write_protection
> + * update settings
> + * call ftm_set_write_protection
> + * release mutex
> + */
> +static void ftm_clear_write_protection(struct ftm_quaddec *ftm)
> +{
> +	uint32_t flag;
> +
> +	/* First see if it is enabled */
> +	ftm_read(ftm, FTM_FMS, &flag);
> +
> +	if (flag & FTM_FMS_WPEN) {
> +		ftm_read(ftm, FTM_MODE, &flag);
> +		ftm_write(ftm, FTM_MODE, flag | FTM_MODE_WPDIS);
> +	}
> +}
> +
> +static void ftm_set_write_protection(struct ftm_quaddec *ftm)
> +{
> +	ftm_write(ftm, FTM_FMS, FTM_FMS_WPEN);
> +}
> +
> +static void ftm_reset_counter(struct ftm_quaddec *ftm)
> +{
> +	/* Reset hardware counter to CNTIN */
> +	ftm_write(ftm, FTM_CNT, 0x0);
> +}
> +
> +static void ftm_quaddec_init(struct ftm_quaddec *ftm)
> +{
> +	ftm_clear_write_protection(ftm);
> +
> +	/* Do not write in the region from the CNTIN register through the
IIO multiline syntax is
/*
 * Do not write
 * PWM..
 */
> +	 * PWMLOAD register when FTMEN = 0.
> +	 */
> +	ftm_write(ftm, FTM_MODE, FTM_MODE_FTMEN); /* enable FTM */

Drop any comments that are self explanatory.

> +	ftm_write(ftm, FTM_CNTIN, 0x0000);         /* zero init value */
> +	ftm_write(ftm, FTM_MOD, 0xffff);        /* max overflow value */
> +	ftm_write(ftm, FTM_CNT, 0x0);           /* reset counter value */
> +	ftm_write(ftm, FTM_SC, FTM_SC_PS_1);    /* prescale with x1 */
> +	/* Select quad mode */
> +	ftm_write(ftm, FTM_QDCTRL, FTM_QDCTRL_QUADEN);
> +
> +	/* Unused features and reset to default section */
> +	ftm_write(ftm, FTM_POL, 0x0);     /* polarity is active high */
> +	ftm_write(ftm, FTM_FLTCTRL, 0x0); /* all faults disabled */
> +	ftm_write(ftm, FTM_SYNCONF, 0x0); /* disable all sync */
> +	ftm_write(ftm, FTM_SYNC, 0xffff);
> +
> +	/* Lock the FTM */
> +	ftm_set_write_protection(ftm);
> +}
> +
> +static int ftm_quaddec_read_raw(struct iio_dev *indio_dev,
> +				struct iio_chan_spec const *chan,
> +				int *val, int *val2, long mask)
> +{
> +	struct ftm_quaddec *ftm = iio_priv(indio_dev);
> +	uint32_t counter;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ftm_read(ftm, FTM_CNT, &counter);
> +		*val = counter;
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static ssize_t ftm_write_reset(struct iio_dev *indio_dev,
> +				uintptr_t private,
> +				struct iio_chan_spec const *chan,
> +				const char *buf, size_t len)
> +{
> +	struct ftm_quaddec *ftm = iio_priv(indio_dev);
> +
> +	/* Only "counter reset" is supported for now */
> +	if (!sysfs_streq(buf, "0")) {
> +		dev_warn(&ftm->pdev->dev, "Reset only accepts '0'\n");
> +		return -EINVAL;

Why not just make the channel attribute itself writeable given we are
setting it to 0?

> +	}
> +
> +	ftm_reset_counter(ftm);
> +
> +	return len;
> +}
> +
> +static int ftm_quaddec_get_prescaler(struct iio_dev *indio_dev,
> +					const struct iio_chan_spec *chan)
> +{
> +	struct ftm_quaddec *ftm = iio_priv(indio_dev);
> +	uint32_t scflags;
> +
> +	ftm_read(ftm, FTM_SC, &scflags);
> +
> +	return scflags & FTM_SC_PS_MASK;
> +}
> +
> +static int ftm_quaddec_set_prescaler(struct iio_dev *indio_dev,
> +					const struct iio_chan_spec *chan,
> +					unsigned int type)
> +{
> +	struct ftm_quaddec *ftm = iio_priv(indio_dev);
> +
> +	uint32_t scflags;
> +
> +	mutex_lock(&ftm->ftm_quaddec_mutex);
> +
> +	ftm_read(ftm, FTM_SC, &scflags);
> +
> +	scflags &= ~FTM_SC_PS_MASK;
> +	type &= FTM_SC_PS_MASK; /*just to be 100% sure*/
> +
> +	scflags |= type;
> +
> +	/* Write */
> +	ftm_clear_write_protection(ftm);
> +	ftm_write(ftm, FTM_SC, scflags);
> +	ftm_set_write_protection(ftm);
> +
> +	/* Also resets the counter as it is undefined anyway now */
> +	ftm_reset_counter(ftm);
> +
> +	mutex_unlock(&ftm->ftm_quaddec_mutex);
> +	return 0;
> +}
> +
> +static const char * const ftm_quaddec_prescaler[] = {
> +	"1", "2", "4", "8", "16", "32", "64", "128"
> +};
> +
> +static const struct iio_enum ftm_quaddec_prescaler_en = {
> +	.items = ftm_quaddec_prescaler,
> +	.num_items = ARRAY_SIZE(ftm_quaddec_prescaler),
> +	.get = ftm_quaddec_get_prescaler,
> +	.set = ftm_quaddec_set_prescaler,
> +};
> +
> +static const struct iio_chan_spec_ext_info ftm_quaddec_ext_info[] = {
> +	{
> +		.name = "reset",
> +		.shared = IIO_SEPARATE,
> +		.write = ftm_write_reset,
> +	},
> +	IIO_ENUM("prescaler", IIO_SEPARATE, &ftm_quaddec_prescaler_en),

This looks like non standard ABI.  Needs documentation in
Documentation/ABI/testing/sysfs-bus-iio-*

> +	IIO_ENUM_AVAILABLE("prescaler", &ftm_quaddec_prescaler_en),
> +	{}
> +};
> +
> +static const struct iio_chan_spec ftm_quaddec_channels = {
> +	.type = IIO_COUNT,
> +	.channel = 0,
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +	.ext_info = ftm_quaddec_ext_info,
> +	.indexed = 1,
> +};
> +
> +static const struct iio_info ftm_quaddec_iio_info = {
> +	.read_raw = ftm_quaddec_read_raw,
> +};
> +
> +static int ftm_quaddec_probe(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev;
> +	struct ftm_quaddec *ftm;
> +	int ret;
> +
> +	struct device_node *node = pdev->dev.of_node;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*ftm));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	ftm = iio_priv(indio_dev);
> +
> +	platform_set_drvdata(pdev, ftm);
> +
> +	ftm->pdev = pdev;
> +	ftm->big_endian = of_property_read_bool(node, "big-endian");
> +	ftm->ftm_base = of_iomap(node, 0);
> +	if (!ftm->ftm_base)
> +		return -EINVAL;
> +
> +	indio_dev->name = dev_name(&pdev->dev);

This should be a nice part number like string.  What does
it evaluate to here?

> +	indio_dev->dev.parent = &pdev->dev;
> +	indio_dev->info = &ftm_quaddec_iio_info;
> +	indio_dev->num_channels = 1;
> +	indio_dev->channels = &ftm_quaddec_channels;
> +
> +	ftm_quaddec_init(ftm);
> +
> +	mutex_init(&ftm->ftm_quaddec_mutex);
> +
> +	ret = devm_iio_device_register(&pdev->dev, indio_dev);
> +	if (ret) {
> +		mutex_destroy(&ftm->ftm_quaddec_mutex);

Don't have managed devm_ calls after anything unmanaged.
I opens you up to races and is hard to review.

> +		iounmap(ftm->ftm_base);
I would suggest not using of_iomap, then you can
use the devm_ioremap form handle this for you.

> +	}
> +	return ret;
> +}
> +
> +static int ftm_quaddec_remove(struct platform_device *pdev)
> +{
> +	struct ftm_quaddec *ftm;
> +	struct iio_dev *indio_dev;
> +
> +	ftm = (struct ftm_quaddec *)platform_get_drvdata(pdev);

platform_get_drvdata returns a void *.

C spec says you can always cast implicitly from a void * to any
other point type.  Hence you don't need the cast.
(I'm too lazy to find the reference now as it's been a long
day of reviewing but google will find it for you if interested)

> +	indio_dev = iio_priv_to_dev(ftm);
> +	/* This is needed to remove sysfs entries */

It does a lot more than that, so please remove the comment.
Actually this worries me.  You should not need to manually
call devm_iio_device_register, but you do because of the ordering
and the fact you want to remove the interfaces before turning the
device off.  In that case, do not use the devm_ form but
instead iio_device_register and do the error handling paths
manually.  An alternative is to use
devm_add_action_or_reset to call unwind functions automatically
for the few device specific calls you have.


> +	devm_iio_device_unregister(&pdev->dev, indio_dev);
> +
> +	ftm_write(ftm, FTM_MODE, 0);
> +
> +	iounmap(ftm->ftm_base);
> +	mutex_destroy(&ftm->ftm_quaddec_mutex);

mutex destroy is only really used in debug paths and is often
skipped in remove functions to simplify things.
(particularly when managed cleanup is going on).

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id ftm_quaddec_match[] = {
> +	{ .compatible = "fsl,ftm-quaddec" },
> +	{},
> +};
> +
> +static struct platform_driver ftm_quaddec_driver = {
> +	.driver = {
> +		.name = "ftm-quaddec",
> +		.owner = THIS_MODULE,
> +		.of_match_table = ftm_quaddec_match,
> +	},
> +	.probe = ftm_quaddec_probe,
> +	.remove = ftm_quaddec_remove,
> +};
> +
> +module_platform_driver(ftm_quaddec_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Kjeld Flarup <[e-mail]");
> +MODULE_AUTHOR("Patrick Havelange <[e-mail]");

William Breathitt Gray Feb. 21, 2019, 1:09 a.m. UTC | #2

On Wed, Feb 20, 2019 at 04:41:54PM +0000, Jonathan Cameron wrote:
> On Mon, 18 Feb 2019 15:03:18 +0100
> Patrick Havelange <[e-mail]> wrote:
> 
> > This driver exposes the counter for the quadrature decoder of the
> > FlexTimer Module, present in the LS1021A soc.
> > 
> > Signed-off-by: Patrick Havelange <[e-mail]>
> > Reviewed-by: Esben Haabendal <[e-mail]>
> Given you cc'd William, I'm guessing you know about the counter
> subsystem effort.  I would really rather not take any drivers
> into IIO if we have any hope of getting that upstreamed soon
> (which I personally think we do and should!).  The reason is
> we end up having to maintain old ABI just because someone might be using
> it and it makes the drivers very messy.
> 
> I'll review as is though as may be there are some elements that will
> cross over.
> 
> Comments inline.  William: Looks like a straight forward conversion if
> it makes sense to get this lined up as part of your initial submission?
> You have quite a few drivers so I wouldn't have said it needs to be there
> at the start, but good to have it soon after.
> 
> Jonathan

I agree, we should try to merge this as part of Counter subsystem
introduction rather than as another IIO Counter driver. As we determined
when adding support for the STM32 timers, the existing IIO Counter API
is fundamentally unsuitable for representing counter devices. So
regardless of how a new Counter API is merged, the existing IIO Counter
API must be deprecated.

Patrick, I apologize for the confusion this has caused. Would you be
able to convert this driver to use the proposed Counter subsystem API
from this patchset that I believe you encountered before:
https://marc.info/?l=linux-arm-kernel&m=153229982404051

Although it was last updated in October, I believe you should be able to
rebase that Counter subsystem introduction patchset cleanly on top of
the IIO tree (if there are any merge conflicts send me an email). Take a
look at the generic-counter.rst file under the Documentation/driver-api/
directory for an overview of the API; the counter drivers under the
drivers/counter/ directory also make good references.

If you have any difficulties understanding the API, or any other
troubles, don't hesitate to ask. Hopefully, I've made the documentation
clear enough to make the conversion of this driver quick and easy -- and
if not, then it's something I need to fix, so let me know. :-)

William Breathitt Gray

William Breathitt Gray Feb. 21, 2019, 8:28 a.m. UTC | #3

On Thu, Feb 21, 2019 at 10:09:54AM +0900, William Breathitt Gray wrote:
> On Wed, Feb 20, 2019 at 04:41:54PM +0000, Jonathan Cameron wrote:
> > On Mon, 18 Feb 2019 15:03:18 +0100
> > Patrick Havelange <[e-mail]> wrote:
> > 
> > > This driver exposes the counter for the quadrature decoder of the
> > > FlexTimer Module, present in the LS1021A soc.
> > > 
> > > Signed-off-by: Patrick Havelange <[e-mail]>
> > > Reviewed-by: Esben Haabendal <[e-mail]>
> > Given you cc'd William, I'm guessing you know about the counter
> > subsystem effort.  I would really rather not take any drivers
> > into IIO if we have any hope of getting that upstreamed soon
> > (which I personally think we do and should!).  The reason is
> > we end up having to maintain old ABI just because someone might be using
> > it and it makes the drivers very messy.
> > 
> > I'll review as is though as may be there are some elements that will
> > cross over.
> > 
> > Comments inline.  William: Looks like a straight forward conversion if
> > it makes sense to get this lined up as part of your initial submission?
> > You have quite a few drivers so I wouldn't have said it needs to be there
> > at the start, but good to have it soon after.
> > 
> > Jonathan
> 
> I agree, we should try to merge this as part of Counter subsystem
> introduction rather than as another IIO Counter driver. As we determined
> when adding support for the STM32 timers, the existing IIO Counter API
> is fundamentally unsuitable for representing counter devices. So
> regardless of how a new Counter API is merged, the existing IIO Counter
> API must be deprecated.
> 
> Patrick, I apologize for the confusion this has caused. Would you be
> able to convert this driver to use the proposed Counter subsystem API
> from this patchset that I believe you encountered before:
> https://marc.info/?l=linux-arm-kernel&m=153229982404051
> 
> Although it was last updated in October, I believe you should be able to
> rebase that Counter subsystem introduction patchset cleanly on top of
> the IIO tree (if there are any merge conflicts send me an email). Take a
> look at the generic-counter.rst file under the Documentation/driver-api/
> directory for an overview of the API; the counter drivers under the
> drivers/counter/ directory also make good references.
> 
> If you have any difficulties understanding the API, or any other
> troubles, don't hesitate to ask. Hopefully, I've made the documentation
> clear enough to make the conversion of this driver quick and easy -- and
> if not, then it's something I need to fix, so let me know. :-)
> 
> William Breathitt Gray

Patrick,

It looks like there were some minor conflicts with the v9 patchset, so
I've rebased it on top of the latest iio tree testing branch and
resolved the conflicts in my personal repository. Please pull from my
personal repository at https://gitlab.com/vilhelmgray/iio.git and base
your patches on top of the generic_counter_v10 branch.

William Breathitt Gray

Patrick Havelange Feb. 22, 2019, 2:37 p.m. UTC | #4

Hi Jonathan,

Thanks for your comments, I'll make a new version of the patch based
on your input.

William, I'll rebase the next version on top of your branch.

I'm glad the counter subsystem effort is progressing :)


Patrick Havelange.

On Thu, Feb 21, 2019 at 9:27 AM William Breathitt Gray
<[e-mail]> wrote:
>
> On Thu, Feb 21, 2019 at 10:09:54AM +0900, William Breathitt Gray wrote:
> > On Wed, Feb 20, 2019 at 04:41:54PM +0000, Jonathan Cameron wrote:
> > > On Mon, 18 Feb 2019 15:03:18 +0100
> > > Patrick Havelange <[e-mail]> wrote:
> > >
> > > > This driver exposes the counter for the quadrature decoder of the
> > > > FlexTimer Module, present in the LS1021A soc.
> > > >
> > > > Signed-off-by: Patrick Havelange <[e-mail]>
> > > > Reviewed-by: Esben Haabendal <[e-mail]>
> > > Given you cc'd William, I'm guessing you know about the counter
> > > subsystem effort.  I would really rather not take any drivers
> > > into IIO if we have any hope of getting that upstreamed soon
> > > (which I personally think we do and should!).  The reason is
> > > we end up having to maintain old ABI just because someone might be using
> > > it and it makes the drivers very messy.
> > >
> > > I'll review as is though as may be there are some elements that will
> > > cross over.
> > >
> > > Comments inline.  William: Looks like a straight forward conversion if
> > > it makes sense to get this lined up as part of your initial submission?
> > > You have quite a few drivers so I wouldn't have said it needs to be there
> > > at the start, but good to have it soon after.
> > >
> > > Jonathan
> >
> > I agree, we should try to merge this as part of Counter subsystem
> > introduction rather than as another IIO Counter driver. As we determined
> > when adding support for the STM32 timers, the existing IIO Counter API
> > is fundamentally unsuitable for representing counter devices. So
> > regardless of how a new Counter API is merged, the existing IIO Counter
> > API must be deprecated.
> >
> > Patrick, I apologize for the confusion this has caused. Would you be
> > able to convert this driver to use the proposed Counter subsystem API
> > from this patchset that I believe you encountered before:
> > https://marc.info/?l=linux-arm-kernel&m=153229982404051
> >
> > Although it was last updated in October, I believe you should be able to
> > rebase that Counter subsystem introduction patchset cleanly on top of
> > the IIO tree (if there are any merge conflicts send me an email). Take a
> > look at the generic-counter.rst file under the Documentation/driver-api/
> > directory for an overview of the API; the counter drivers under the
> > drivers/counter/ directory also make good references.
> >
> > If you have any difficulties understanding the API, or any other
> > troubles, don't hesitate to ask. Hopefully, I've made the documentation
> > clear enough to make the conversion of this driver quick and easy -- and
> > if not, then it's something I need to fix, so let me know. :-)
> >
> > William Breathitt Gray
>
> Patrick,
>
> It looks like there were some minor conflicts with the v9 patchset, so
> I've rebased it on top of the latest iio tree testing branch and
> resolved the conflicts in my personal repository. Please pull from my
> personal repository at https://gitlab.com/vilhelmgray/iio.git and base
> your patches on top of the generic_counter_v10 branch.
>
> William Breathitt Gray

Patrick Havelange March 4, 2019, 12:36 p.m. UTC | #5

On Wed, Feb 20, 2019 at 5:42 PM Jonathan Cameron <[e-mail]> wrote:
[skipped]
> > +
> > +struct ftm_quaddec {
> > +     struct platform_device *pdev;
> > +     void __iomem *ftm_base;
> > +     bool big_endian;
>
> I'm curious. What is the benefit of running in big endian mode?

It is based on the same behaviour as in drivers/clocksource/timer-fsl-ftm.c
The FlexTimer itself on the board I'm testing it with is working in
big endian mode, so this mode is required.

> > +static ssize_t ftm_write_reset(struct iio_dev *indio_dev,
> > +                             uintptr_t private,
> > +                             struct iio_chan_spec const *chan,
> > +                             const char *buf, size_t len)
> > +{
> > +     struct ftm_quaddec *ftm = iio_priv(indio_dev);
> > +
> > +     /* Only "counter reset" is supported for now */
> > +     if (!sysfs_streq(buf, "0")) {
> > +             dev_warn(&ftm->pdev->dev, "Reset only accepts '0'\n");
> > +             return -EINVAL;
>
> Why not just make the channel attribute itself writeable given we are
> setting it to 0?

Good idea, I'll see if this can be applied in the new subsystem.

[skipped]

All other comments are Acked.

Patch

diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
index bf1e559ad7cd..4641cb2e752a 100644
--- a/drivers/iio/counter/Kconfig
+++ b/drivers/iio/counter/Kconfig
@@ -31,4 +31,14 @@  config STM32_LPTIMER_CNT
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called stm32-lptimer-cnt.
+
+config FTM_QUADDEC
+	tristate "Flex Timer Module Quadrature decoder driver"
+	help
+	  Select this option to enable the Flex Timer Quadrature decoder
+	  driver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ftm-quaddec.
+
 endmenu
diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
index 1b9a896eb488..757c1f4196af 100644
--- a/drivers/iio/counter/Makefile
+++ b/drivers/iio/counter/Makefile
@@ -6,3 +6,4 @@ 
 
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
+obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
diff --git a/drivers/iio/counter/ftm-quaddec.c b/drivers/iio/counter/ftm-quaddec.c
new file mode 100644
index 000000000000..ca7e55a9ab3f
--- /dev/null
+++ b/drivers/iio/counter/ftm-quaddec.c
@@ -0,0 +1,294 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Flex Timer Module Quadrature decoder
+ *
+ * This module implements a driver for decoding the FTM quadrature
+ * of ex. a LS1021A
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/workqueue.h>
+#include <linux/swait.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/mutex.h>
+#include <linux/fsl/ftm.h>
+
+struct ftm_quaddec {
+	struct platform_device *pdev;
+	void __iomem *ftm_base;
+	bool big_endian;
+	struct mutex ftm_quaddec_mutex;
+};
+
+#define HASFLAGS(flag, bits) ((flag & bits) ? 1 : 0)
+
+#define DEFAULT_POLL_INTERVAL    100 /* in msec */
+
+static void ftm_read(struct ftm_quaddec *ftm, uint32_t offset, uint32_t *data)
+{
+	if (ftm->big_endian)
+		*data = ioread32be(ftm->ftm_base + offset);
+	else
+		*data = ioread32(ftm->ftm_base + offset);
+}
+
+static void ftm_write(struct ftm_quaddec *ftm, uint32_t offset, uint32_t data)
+{
+	if (ftm->big_endian)
+		iowrite32be(data, ftm->ftm_base + offset);
+	else
+		iowrite32(data, ftm->ftm_base + offset);
+}
+
+/* take mutex
+ * call ftm_clear_write_protection
+ * update settings
+ * call ftm_set_write_protection
+ * release mutex
+ */
+static void ftm_clear_write_protection(struct ftm_quaddec *ftm)
+{
+	uint32_t flag;
+
+	/* First see if it is enabled */
+	ftm_read(ftm, FTM_FMS, &flag);
+
+	if (flag & FTM_FMS_WPEN) {
+		ftm_read(ftm, FTM_MODE, &flag);
+		ftm_write(ftm, FTM_MODE, flag | FTM_MODE_WPDIS);
+	}
+}
+
+static void ftm_set_write_protection(struct ftm_quaddec *ftm)
+{
+	ftm_write(ftm, FTM_FMS, FTM_FMS_WPEN);
+}
+
+static void ftm_reset_counter(struct ftm_quaddec *ftm)
+{
+	/* Reset hardware counter to CNTIN */
+	ftm_write(ftm, FTM_CNT, 0x0);
+}
+
+static void ftm_quaddec_init(struct ftm_quaddec *ftm)
+{
+	ftm_clear_write_protection(ftm);
+
+	/* Do not write in the region from the CNTIN register through the
+	 * PWMLOAD register when FTMEN = 0.
+	 */
+	ftm_write(ftm, FTM_MODE, FTM_MODE_FTMEN); /* enable FTM */
+	ftm_write(ftm, FTM_CNTIN, 0x0000);         /* zero init value */
+	ftm_write(ftm, FTM_MOD, 0xffff);        /* max overflow value */
+	ftm_write(ftm, FTM_CNT, 0x0);           /* reset counter value */
+	ftm_write(ftm, FTM_SC, FTM_SC_PS_1);    /* prescale with x1 */
+	/* Select quad mode */
+	ftm_write(ftm, FTM_QDCTRL, FTM_QDCTRL_QUADEN);
+
+	/* Unused features and reset to default section */
+	ftm_write(ftm, FTM_POL, 0x0);     /* polarity is active high */
+	ftm_write(ftm, FTM_FLTCTRL, 0x0); /* all faults disabled */
+	ftm_write(ftm, FTM_SYNCONF, 0x0); /* disable all sync */
+	ftm_write(ftm, FTM_SYNC, 0xffff);
+
+	/* Lock the FTM */
+	ftm_set_write_protection(ftm);
+}
+
+static int ftm_quaddec_read_raw(struct iio_dev *indio_dev,
+				struct iio_chan_spec const *chan,
+				int *val, int *val2, long mask)
+{
+	struct ftm_quaddec *ftm = iio_priv(indio_dev);
+	uint32_t counter;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ftm_read(ftm, FTM_CNT, &counter);
+		*val = counter;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static ssize_t ftm_write_reset(struct iio_dev *indio_dev,
+				uintptr_t private,
+				struct iio_chan_spec const *chan,
+				const char *buf, size_t len)
+{
+	struct ftm_quaddec *ftm = iio_priv(indio_dev);
+
+	/* Only "counter reset" is supported for now */
+	if (!sysfs_streq(buf, "0")) {
+		dev_warn(&ftm->pdev->dev, "Reset only accepts '0'\n");
+		return -EINVAL;
+	}
+
+	ftm_reset_counter(ftm);
+
+	return len;
+}
+
+static int ftm_quaddec_get_prescaler(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan)
+{
+	struct ftm_quaddec *ftm = iio_priv(indio_dev);
+	uint32_t scflags;
+
+	ftm_read(ftm, FTM_SC, &scflags);
+
+	return scflags & FTM_SC_PS_MASK;
+}
+
+static int ftm_quaddec_set_prescaler(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan,
+					unsigned int type)
+{
+	struct ftm_quaddec *ftm = iio_priv(indio_dev);
+
+	uint32_t scflags;
+
+	mutex_lock(&ftm->ftm_quaddec_mutex);
+
+	ftm_read(ftm, FTM_SC, &scflags);
+
+	scflags &= ~FTM_SC_PS_MASK;
+	type &= FTM_SC_PS_MASK; /*just to be 100% sure*/
+
+	scflags |= type;
+
+	/* Write */
+	ftm_clear_write_protection(ftm);
+	ftm_write(ftm, FTM_SC, scflags);
+	ftm_set_write_protection(ftm);
+
+	/* Also resets the counter as it is undefined anyway now */
+	ftm_reset_counter(ftm);
+
+	mutex_unlock(&ftm->ftm_quaddec_mutex);
+	return 0;
+}
+
+static const char * const ftm_quaddec_prescaler[] = {
+	"1", "2", "4", "8", "16", "32", "64", "128"
+};
+
+static const struct iio_enum ftm_quaddec_prescaler_en = {
+	.items = ftm_quaddec_prescaler,
+	.num_items = ARRAY_SIZE(ftm_quaddec_prescaler),
+	.get = ftm_quaddec_get_prescaler,
+	.set = ftm_quaddec_set_prescaler,
+};
+
+static const struct iio_chan_spec_ext_info ftm_quaddec_ext_info[] = {
+	{
+		.name = "reset",
+		.shared = IIO_SEPARATE,
+		.write = ftm_write_reset,
+	},
+	IIO_ENUM("prescaler", IIO_SEPARATE, &ftm_quaddec_prescaler_en),
+	IIO_ENUM_AVAILABLE("prescaler", &ftm_quaddec_prescaler_en),
+	{}
+};
+
+static const struct iio_chan_spec ftm_quaddec_channels = {
+	.type = IIO_COUNT,
+	.channel = 0,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+	.ext_info = ftm_quaddec_ext_info,
+	.indexed = 1,
+};
+
+static const struct iio_info ftm_quaddec_iio_info = {
+	.read_raw = ftm_quaddec_read_raw,
+};
+
+static int ftm_quaddec_probe(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev;
+	struct ftm_quaddec *ftm;
+	int ret;
+
+	struct device_node *node = pdev->dev.of_node;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*ftm));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	ftm = iio_priv(indio_dev);
+
+	platform_set_drvdata(pdev, ftm);
+
+	ftm->pdev = pdev;
+	ftm->big_endian = of_property_read_bool(node, "big-endian");
+	ftm->ftm_base = of_iomap(node, 0);
+	if (!ftm->ftm_base)
+		return -EINVAL;
+
+	indio_dev->name = dev_name(&pdev->dev);
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->info = &ftm_quaddec_iio_info;
+	indio_dev->num_channels = 1;
+	indio_dev->channels = &ftm_quaddec_channels;
+
+	ftm_quaddec_init(ftm);
+
+	mutex_init(&ftm->ftm_quaddec_mutex);
+
+	ret = devm_iio_device_register(&pdev->dev, indio_dev);
+	if (ret) {
+		mutex_destroy(&ftm->ftm_quaddec_mutex);
+		iounmap(ftm->ftm_base);
+	}
+	return ret;
+}
+
+static int ftm_quaddec_remove(struct platform_device *pdev)
+{
+	struct ftm_quaddec *ftm;
+	struct iio_dev *indio_dev;
+
+	ftm = (struct ftm_quaddec *)platform_get_drvdata(pdev);
+	indio_dev = iio_priv_to_dev(ftm);
+	/* This is needed to remove sysfs entries */
+	devm_iio_device_unregister(&pdev->dev, indio_dev);
+
+	ftm_write(ftm, FTM_MODE, 0);
+
+	iounmap(ftm->ftm_base);
+	mutex_destroy(&ftm->ftm_quaddec_mutex);
+
+	return 0;
+}
+
+static const struct of_device_id ftm_quaddec_match[] = {
+	{ .compatible = "fsl,ftm-quaddec" },
+	{},
+};
+
+static struct platform_driver ftm_quaddec_driver = {
+	.driver = {
+		.name = "ftm-quaddec",
+		.owner = THIS_MODULE,
+		.of_match_table = ftm_quaddec_match,
+	},
+	.probe = ftm_quaddec_probe,
+	.remove = ftm_quaddec_remove,
+};
+
+module_platform_driver(ftm_quaddec_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Kjeld Flarup <[e-mail]");
+MODULE_AUTHOR("Patrick Havelange <[e-mail]");