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Date:   Mon, 11 Mar 2019 12:24:04 +0000
From:   Jonathan Cameron <jonathan.cameron@huawei.com>
To:     Patrick Havelange <patrick.havelange@essensium.com>
CC:     William Breathitt Gray <vilhelm.gray@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Thierry Reding" <thierry.reding@gmail.com>,
        Esben Haabendal <esben@haabendal.dk>,
        <linux-iio@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-pwm@vger.kernel.org>, <linuxppc-dev@lists.ozlabs.org>,
        "Jonathan Cameron" <jic23@kernel.org>
Subject: Re: [PATCH v2 5/7] counter: add FlexTimer Module Quadrature decoder
 counter driver
Message-ID: <20190311122404.0000546f@huawei.com>
In-Reply-To: <20190306111208.7454-6-patrick.havelange@essensium.com>
References: <20190306111208.7454-1-patrick.havelange@essensium.com>
        <20190306111208.7454-6-patrick.havelange@essensium.com>
Organization: Huawei
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On Wed, 6 Mar 2019 12:12:06 +0100
Patrick Havelange <patrick.havelange@essensium.com> wrote:

> This driver exposes the counter for the quadrature decoder of the
> FlexTimer Module, present in the LS1021A soc.
> 
> Signed-off-by: Patrick Havelange <patrick.havelange@essensium.com>
A few really trivial bits inline to add to William's feedback.

Otherwise I'm happy enough,

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> Changes v2
>  - Rebased on new counter subsystem
>  - Cleaned up included headers
>  - Use devm_ioremap()
>  - Correct order of devm_ and unmanaged resources
> ---
>  drivers/counter/Kconfig       |   9 +
>  drivers/counter/Makefile      |   1 +
>  drivers/counter/ftm-quaddec.c | 356 ++++++++++++++++++++++++++++++++++
>  3 files changed, 366 insertions(+)
>  create mode 100644 drivers/counter/ftm-quaddec.c
> 
> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> index 87c491a19c63..233ac305d878 100644
> --- a/drivers/counter/Kconfig
> +++ b/drivers/counter/Kconfig
> @@ -48,4 +48,13 @@ 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.
> +
>  endif # COUNTER
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> index 5589976d37f8..0c9e622a6bea 100644
> --- a/drivers/counter/Makefile
> +++ b/drivers/counter/Makefile
> @@ -7,3 +7,4 @@ obj-$(CONFIG_COUNTER) += counter.o
>  obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
>  obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
>  obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
> +obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
> diff --git a/drivers/counter/ftm-quaddec.c b/drivers/counter/ftm-quaddec.c
> new file mode 100644
> index 000000000000..1bc9e075a386
> --- /dev/null
> +++ b/drivers/counter/ftm-quaddec.c
> @@ -0,0 +1,356 @@
> +// 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/fsl/ftm.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/io.h>
> +#include <linux/mutex.h>
> +#include <linux/counter.h>
> +
> +struct ftm_quaddec {
> +	struct counter_device counter;
> +	struct platform_device *pdev;
> +	void __iomem *ftm_base;
> +	bool big_endian;
> +	struct mutex ftm_quaddec_mutex;
> +};
> +
> +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);
> +	ftm_write(ftm, FTM_CNTIN, 0x0000);
> +	ftm_write(ftm, FTM_MOD, 0xffff);
> +	ftm_write(ftm, FTM_CNT, 0x0);
> +	ftm_write(ftm, FTM_SC, FTM_SC_PS_1);
> +
> +	/* Select quad mode */
> +	ftm_write(ftm, FTM_QDCTRL, FTM_QDCTRL_QUADEN);
> +
> +	/* Unused features and reset to default section */
> +	ftm_write(ftm, FTM_POL, 0x0);
> +	ftm_write(ftm, FTM_FLTCTRL, 0x0);
> +	ftm_write(ftm, FTM_SYNCONF, 0x0);
> +	ftm_write(ftm, FTM_SYNC, 0xffff);
> +
> +	/* Lock the FTM */
> +	ftm_set_write_protection(ftm);
> +}
> +
> +static void ftm_quaddec_disable(struct ftm_quaddec *ftm)
> +{
> +	ftm_write(ftm, FTM_MODE, 0);
> +}
> +
> +static int ftm_quaddec_get_prescaler(struct counter_device *counter,
> +				     struct counter_count *count,
> +				     size_t *cnt_mode)
> +{
> +	struct ftm_quaddec *ftm = counter->priv;
> +	uint32_t scflags;
> +
> +	ftm_read(ftm, FTM_SC, &scflags);
> +
> +	*cnt_mode = scflags & FTM_SC_PS_MASK;

FIELD_GET and FIELD_PREP are a tidy way of doing these sorts of
accesses. Helpfully they also save a reviewer having to sanity
check that the offset is 0 as it is here.


> +
> +	return 0;
> +}
> +
> +static int ftm_quaddec_set_prescaler(struct counter_device *counter,
> +				     struct counter_count *count,
> +				     size_t cnt_mode)
> +{
> +	struct ftm_quaddec *ftm = counter->priv;
> +
> +	uint32_t scflags;
> +
> +	mutex_lock(&ftm->ftm_quaddec_mutex);
> +
> +	ftm_read(ftm, FTM_SC, &scflags);
> +
> +	scflags &= ~FTM_SC_PS_MASK;
> +	cnt_mode &= FTM_SC_PS_MASK; /*just to be 100% sure*/

nitpick: Comment syntax is /* just to be 100% sure */

> +
> +	scflags |= cnt_mode;
> +
> +	/* 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 struct counter_count_enum_ext ftm_quaddec_prescaler_enum = {
> +	.items = ftm_quaddec_prescaler,
> +	.num_items = ARRAY_SIZE(ftm_quaddec_prescaler),
> +	.get = ftm_quaddec_get_prescaler,
> +	.set = ftm_quaddec_set_prescaler
> +};
> +
> +enum ftm_quaddec_synapse_action {
> +	FTM_QUADDEC_SYNAPSE_ACTION_BOTH_EDGES,
> +};
> +
> +static enum counter_synapse_action ftm_quaddec_synapse_actions[] = {
> +	[FTM_QUADDEC_SYNAPSE_ACTION_BOTH_EDGES] =
> +	COUNTER_SYNAPSE_ACTION_BOTH_EDGES
> +};
> +
> +enum ftm_quaddec_count_function {
> +	FTM_QUADDEC_COUNT_ENCODER_MODE_1,
> +};
> +
> +static const enum counter_count_function ftm_quaddec_count_functions[] = {
> +	[FTM_QUADDEC_COUNT_ENCODER_MODE_1] =
> +	COUNTER_COUNT_FUNCTION_QUADRATURE_X4
> +};
> +
> +static int ftm_quaddec_count_read(struct counter_device *counter,
> +				  struct counter_count *count,
> +				  struct counter_count_read_value *val)
> +{
> +	struct ftm_quaddec *const ftm = counter->priv;
> +	uint32_t cntval;
> +
> +	ftm_read(ftm, FTM_CNT, &cntval);
> +
> +	counter_count_read_value_set(val, COUNTER_COUNT_POSITION, &cntval);
> +
> +	return 0;
> +}
> +
> +static int ftm_quaddec_count_write(struct counter_device *counter,
> +				   struct counter_count *count,
> +				   struct counter_count_write_value *val)
> +{
> +	struct ftm_quaddec *const ftm = counter->priv;
> +	u32 cnt;
> +	int err;
> +
> +	err = counter_count_write_value_get(&cnt, COUNTER_COUNT_POSITION, val);
> +	if (err)
> +		return err;
> +
> +	if (cnt != 0) {
> +		dev_warn(&ftm->pdev->dev, "Can only accept '0' as new counter value\n");
> +		return -EINVAL;
> +	}
> +
> +	ftm_reset_counter(ftm);
> +
> +	return 0;
> +}
> +
> +static int ftm_quaddec_count_function_get(struct counter_device *counter,
> +					  struct counter_count *count,
> +					  size_t *function)
> +{
> +	*function = FTM_QUADDEC_COUNT_ENCODER_MODE_1;
> +
> +	return 0;
> +}
> +
> +static int ftm_quaddec_action_get(struct counter_device *counter,
> +				  struct counter_count *count,
> +				  struct counter_synapse *synapse,
> +				  size_t *action)
> +{
> +	*action = FTM_QUADDEC_SYNAPSE_ACTION_BOTH_EDGES;
> +
> +	return 0;
> +}
> +
> +static const struct counter_ops ftm_quaddec_cnt_ops = {
> +	.count_read = ftm_quaddec_count_read,
> +	.count_write = ftm_quaddec_count_write,
> +	.function_get = ftm_quaddec_count_function_get,
> +	.action_get = ftm_quaddec_action_get,
> +};
> +
> +static struct counter_signal ftm_quaddec_signals[] = {
> +	{
> +		.id = 0,
> +		.name = "Channel 1 Quadrature A"
> +	},
> +	{
> +		.id = 1,
> +		.name = "Channel 1 Quadrature B"
> +	}
> +};
> +
> +static struct counter_synapse ftm_quaddec_count_synapses[] = {
> +	{
> +		.actions_list = ftm_quaddec_synapse_actions,
> +		.num_actions = ARRAY_SIZE(ftm_quaddec_synapse_actions),
> +		.signal = &ftm_quaddec_signals[0]
> +	},
> +	{
> +		.actions_list = ftm_quaddec_synapse_actions,
> +		.num_actions = ARRAY_SIZE(ftm_quaddec_synapse_actions),
> +		.signal = &ftm_quaddec_signals[1]
> +	}
> +};
> +
> +static const struct counter_count_ext ftm_quaddec_count_ext[] = {
> +	COUNTER_COUNT_ENUM("prescaler", &ftm_quaddec_prescaler_enum),
> +	COUNTER_COUNT_ENUM_AVAILABLE("prescaler", &ftm_quaddec_prescaler_enum),
> +};
> +
> +static struct counter_count ftm_quaddec_counts = {
> +	.id = 0,
> +	.name = "Channel 1 Count",
> +	.functions_list = ftm_quaddec_count_functions,
> +	.num_functions = ARRAY_SIZE(ftm_quaddec_count_functions),
> +	.synapses = ftm_quaddec_count_synapses,
> +	.num_synapses = ARRAY_SIZE(ftm_quaddec_count_synapses),
> +	.ext = ftm_quaddec_count_ext,
> +	.num_ext = ARRAY_SIZE(ftm_quaddec_count_ext)
> +};
> +
> +static int ftm_quaddec_probe(struct platform_device *pdev)
> +{
> +	struct ftm_quaddec *ftm;
> +
> +	struct device_node *node = pdev->dev.of_node;
> +	struct resource *io;
> +	int ret;
> +
> +	ftm = devm_kzalloc(&pdev->dev, sizeof(*ftm), GFP_KERNEL);
> +	if (!ftm)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, ftm);
> +
> +	io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!io) {
> +		dev_err(&pdev->dev, "Failed to get memory region\n");
> +		return -ENODEV;
> +	}
> +
> +	ftm->pdev = pdev;
> +	ftm->big_endian = of_property_read_bool(node, "big-endian");
> +	ftm->ftm_base = devm_ioremap(&pdev->dev, io->start, resource_size(io));
> +
> +	if (!ftm->ftm_base) {
> +		dev_err(&pdev->dev, "Failed to map memory region\n");
> +		return -EINVAL;
> +	}
> +	ftm->counter.name = dev_name(&pdev->dev);
> +	ftm->counter.parent = &pdev->dev;
> +	ftm->counter.ops = &ftm_quaddec_cnt_ops;
> +	ftm->counter.counts = &ftm_quaddec_counts;
> +	ftm->counter.num_counts = 1;
> +	ftm->counter.signals = ftm_quaddec_signals;
> +	ftm->counter.num_signals = ARRAY_SIZE(ftm_quaddec_signals);
> +	ftm->counter.priv = ftm;
> +
> +	mutex_init(&ftm->ftm_quaddec_mutex);
> +
> +	ftm_quaddec_init(ftm);
> +
> +	ret = counter_register(&ftm->counter);
> +	if (ret)
> +		ftm_quaddec_disable(ftm);
> +
> +	return ret;
> +}
> +
> +static int ftm_quaddec_remove(struct platform_device *pdev)
> +{
> +	struct ftm_quaddec *ftm = platform_get_drvdata(pdev);
> +
> +	counter_unregister(&ftm->counter);
> +
> +	ftm_quaddec_disable(ftm);
> +
> +	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,
No need to set this, the call to __platform_driver_register
that comes from the module_platform_driver macro below
will deal with this for you.

> +		.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 <kfa@deif.com");
> +MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com");