Subject: Re: [PATCH v2 3/3] counter: Add atmel TCB capture counter

From: Jonathan Cameron <[email-masked]>
Date: Sun, 12 Apr 2020 11:44:33 +0100

On Thu,  9 Apr 2020 16:14:01 +0200
Kamel Bouhara <[email-masked]> wrote:

> This drivers allows to use the capture mode of the Timer Counter Block
> hardware block available in Atmel SoCs through the counter subsystem.
> 
> Two functions of the counter are supported for the moment: period
> capture and quadrature decoder. The latter is only supported by the
> SAMA5 series of SoCs.
> 
> For the period capture mode a basic setup has been chosen that will
> reset the counter each time the period is actually reached. Of course
> the device offers much more possibilities.
> 
> For quadrature mode, both channel 0 and 1 must be configured even if we
> only capture the position (no revolution/rotation).
> 
> Signed-off-by: Kamel Bouhara <[email-masked]>
Hi Kamel,

An issue around cleanup inline + a few nitpicks.

Otherwise looks good to me.

Jonathan

> ---
> Changes from v2:
>  - Updated return code to -EINVAL when user is requesting qdec mode on
>    a counter device not supporting it.
>  - Added an error case returning -EINVAL when action edge is performed in
>    qdec mode.
>  - Removed no need to explicity setting ops to NULL from static struct as
>    it is the default value.
>  - Changed confusing code by using snprintf for the sake of clarity.
>  - Changed code to use ARRAY_SIZE so that future reviewers will know
>    that num_counts matches what's in the atmel_tc_count array without
>    having to check so themselves.
> 
>  drivers/counter/Kconfig             |  11 +
>  drivers/counter/Makefile            |   1 +
>  drivers/counter/atmel-tcb-capture.c | 394 ++++++++++++++++++++++++++++
>  3 files changed, 406 insertions(+)
>  create mode 100644 drivers/counter/atmel-tcb-capture.c
> 
> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> index c80fa76bb531..c50d7453ec33 100644
> --- a/drivers/counter/Kconfig
> +++ b/drivers/counter/Kconfig
> @@ -70,4 +70,15 @@ config FTM_QUADDEC
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ftm-quaddec.
> 
> +config ATMEL_TCB_CAPTURE
> +	tristate "Atmel Timer Counter Capture driver"
> +	depends on HAS_IOMEM && OF
> +	select REGMAP_MMIO
> +	help
> +	  Select this option to enable the Atmel Timer Counter Block
> +	  capture driver.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called atmel-tcb-capture.
> +
>  endif # COUNTER
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> index 55142d1f4c43..70c5b8924588 100644
> --- a/drivers/counter/Makefile
> +++ b/drivers/counter/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
>  obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
>  obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
>  obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
> +obj-$(CONFIG_ATMEL_TCB_CAPTURE)	+= atmel-tcb-capture.o
> diff --git a/drivers/counter/atmel-tcb-capture.c b/drivers/counter/atmel-tcb-capture.c
> new file mode 100644
> index 000000000000..4f2b3d60584f
> --- /dev/null
> +++ b/drivers/counter/atmel-tcb-capture.c
> @@ -0,0 +1,394 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/**
> + * Copyright (C) 2020 Atmel
> + *
> + * Author: Kamel Bouhara <[email-masked]>
> + *

Nitpick. Blank line doesn't add anything :)

> + */
> +#include <linux/clk.h>
> +#include <linux/counter.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <soc/at91/atmel_tcb.h>
> +
> +#define ATMEL_TC_CMR_MASK	(ATMEL_TC_LDRA_RISING | ATMEL_TC_LDRB_FALLING | \
> +				 ATMEL_TC_ETRGEDG_RISING | ATMEL_TC_LDBDIS | \
> +				 ATMEL_TC_LDBSTOP)
> +
> +#define ATMEL_TC_QDEN			BIT(8)
> +#define ATMEL_TC_POSEN			BIT(9)
> +
> +struct atmel_tc_data {
> +	const struct atmel_tcb_config *tc_cfg;
> +	struct counter_device counter;
> +	struct regmap *regmap;
> +	int qdec_mode;
> +	int num_channels;
> +	int channel[2];
> +	bool trig_inverted;
> +};
> +
> +enum atmel_tc_count_function {
> +	ATMEL_TC_FUNCTION_INCREASE,
> +	ATMEL_TC_FUNCTION_QUADRATURE,
> +};
> +
> +static enum counter_count_function atmel_tc_count_functions[] = {
> +	[ATMEL_TC_FUNCTION_INCREASE] = COUNTER_COUNT_FUNCTION_INCREASE,
> +	[ATMEL_TC_FUNCTION_QUADRATURE] = COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
> +};
> +
> +enum atmel_tc_synapse_action {
> +	ATMEL_TC_SYNAPSE_ACTION_NONE = 0,
> +	ATMEL_TC_SYNAPSE_ACTION_RISING_EDGE,
> +	ATMEL_TC_SYNAPSE_ACTION_FALLING_EDGE,
> +	ATMEL_TC_SYNAPSE_ACTION_BOTH_EDGE
> +};
> +
> +static enum counter_synapse_action atmel_tc_synapse_actions[] = {
> +	[ATMEL_TC_SYNAPSE_ACTION_NONE] = COUNTER_SYNAPSE_ACTION_NONE,
> +	[ATMEL_TC_SYNAPSE_ACTION_RISING_EDGE] = COUNTER_SYNAPSE_ACTION_RISING_EDGE,
> +	[ATMEL_TC_SYNAPSE_ACTION_FALLING_EDGE] = COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
> +	[ATMEL_TC_SYNAPSE_ACTION_BOTH_EDGE] = COUNTER_SYNAPSE_ACTION_BOTH_EDGES,
> +};
> +
> +static struct counter_signal atmel_tc_count_signals[] = {
> +	{
> +		.id = 0,
> +		.name = "Channel A",
> +	},
> +	{
> +		.id = 1,
> +		.name = "Channel B",
> +	}
> +};
> +
> +static struct counter_synapse atmel_tc_count_synapses[] = {
> +	{
> +		.actions_list = atmel_tc_synapse_actions,
> +		.num_actions = ARRAY_SIZE(atmel_tc_synapse_actions),
> +		.signal = &atmel_tc_count_signals[0]
> +	},
> +	{
> +		.actions_list = atmel_tc_synapse_actions,
> +		.num_actions = ARRAY_SIZE(atmel_tc_synapse_actions),
> +		.signal = &atmel_tc_count_signals[1]
> +	}
> +};
> +
> +static int atmel_tc_count_function_get(struct counter_device *counter,
> +				       struct counter_count *count,
> +				       size_t *function)
> +{
> +	struct atmel_tc_data *const priv = counter->priv;
> +
> +	if (priv->qdec_mode)
> +		*function = ATMEL_TC_FUNCTION_QUADRATURE;
> +	else
> +		*function = ATMEL_TC_FUNCTION_INCREASE;
> +
> +	return 0;
> +}
> +
> +static int atmel_tc_count_function_set(struct counter_device *counter,
> +				       struct counter_count *count,
> +				       size_t function)
> +{
> +	struct atmel_tc_data *const priv = counter->priv;
> +	u32 bmr, cmr;
> +
> +	regmap_read(priv->regmap, ATMEL_TC_BMR, &bmr);
> +	regmap_read(priv->regmap, ATMEL_TC_REG(priv->channel[0], CMR), &cmr);
> +
> +	/* Set capture mode */
> +	cmr &= ~ATMEL_TC_WAVE;
> +
> +	switch (function) {
> +	case ATMEL_TC_FUNCTION_INCREASE:
> +		priv->qdec_mode = 0;
> +		/* Set highest rate based on whether soc has gclk or not */
> +		bmr &= ~(ATMEL_TC_QDEN | ATMEL_TC_POSEN);
> +		if (priv->tc_cfg->has_gclk)
> +			cmr |= ATMEL_TC_TIMER_CLOCK2;
> +		else
> +			cmr |= ATMEL_TC_TIMER_CLOCK1;
> +		/* Setup the period capture mode */
> +		cmr |=  ATMEL_TC_CMR_MASK;
> +		cmr &= ~(ATMEL_TC_ABETRG | ATMEL_TC_XC0);
> +		break;
> +	case ATMEL_TC_FUNCTION_QUADRATURE:
> +		if (!priv->tc_cfg->has_qdec)
> +			return -EINVAL;
> +		/* In QDEC mode settings both channels 0 and 1 are required */
> +		if (priv->num_channels < 2 || priv->channel[0] != 0 ||
> +		    priv->channel[1] != 1) {
> +			pr_err("Invalid channels number or id for quadrature mode\n");
> +			return -EINVAL;
> +		}
> +		priv->qdec_mode = 1;
> +		bmr |= ATMEL_TC_QDEN | ATMEL_TC_POSEN;
> +		cmr |= ATMEL_TC_ETRGEDG_RISING | ATMEL_TC_ABETRG | ATMEL_TC_XC0;
> +		break;
> +	}
> +
> +	regmap_write(priv->regmap, ATMEL_TC_BMR, bmr);
> +	regmap_write(priv->regmap, ATMEL_TC_REG(priv->channel[0], CMR), cmr);
> +
> +	/* Enable clock and trigger counter */
> +	regmap_write(priv->regmap, ATMEL_TC_REG(priv->channel[0], CCR),
> +		     ATMEL_TC_CLKEN | ATMEL_TC_SWTRG);
> +
> +	if (priv->qdec_mode) {
> +		regmap_write(priv->regmap,
> +			     ATMEL_TC_REG(priv->channel[1], CMR), cmr);
> +		regmap_write(priv->regmap,
> +			     ATMEL_TC_REG(priv->channel[1], CCR),
> +			     ATMEL_TC_CLKEN | ATMEL_TC_SWTRG);
> +	}
> +
> +	return 0;
> +}
> +
> +static int atmel_tc_count_signal_read(struct counter_device *counter,
> +				      struct counter_signal *signal,
> +				      enum counter_signal_value *val)
> +{
> +	struct atmel_tc_data *const priv = counter->priv;
> +	bool sigstatus;
> +	u32 sr;
> +
> +	regmap_read(priv->regmap, ATMEL_TC_REG(priv->channel[0], SR), &sr);
> +
> +	if (priv->trig_inverted)
> +		sigstatus = (sr & ATMEL_TC_MTIOB);
> +	else
> +		sigstatus = (sr & ATMEL_TC_MTIOA);
> +
> +	*val = sigstatus ? COUNTER_SIGNAL_HIGH : COUNTER_SIGNAL_LOW;
> +
> +	return 0;
> +}
> +
> +static int atmel_tc_count_action_get(struct counter_device *counter,
> +				     struct counter_count *count,
> +				     struct counter_synapse *synapse,
> +				     size_t *action)
> +{
> +	struct atmel_tc_data *const priv = counter->priv;
> +	u32 cmr;
> +
> +	regmap_read(priv->regmap, ATMEL_TC_REG(priv->channel[0], CMR), &cmr);
> +
> +	*action = ATMEL_TC_SYNAPSE_ACTION_NONE;
> +
> +	if (cmr & ATMEL_TC_ETRGEDG_NONE)
> +		*action = ATMEL_TC_SYNAPSE_ACTION_NONE;
> +	else if (cmr & ATMEL_TC_ETRGEDG_RISING)
> +		*action = ATMEL_TC_SYNAPSE_ACTION_RISING_EDGE;
> +	else if (cmr & ATMEL_TC_ETRGEDG_FALLING)
> +		*action = ATMEL_TC_SYNAPSE_ACTION_FALLING_EDGE;
> +	else if (cmr & ATMEL_TC_ETRGEDG_BOTH)
> +		*action = ATMEL_TC_SYNAPSE_ACTION_BOTH_EDGE;
> +
> +	return 0;
> +}
> +
> +static int atmel_tc_count_action_set(struct counter_device *counter,
> +				     struct counter_count *count,
> +				     struct counter_synapse *synapse,
> +				     size_t action)
> +{
> +	struct atmel_tc_data *const priv = counter->priv;
> +	u32 edge = ATMEL_TC_ETRGEDG_NONE;
> +
> +	/* QDEC mode is rising edge only */
> +	if (priv->qdec_mode)
> +		return -EINVAL;
> +
> +	switch (action) {
> +	case ATMEL_TC_SYNAPSE_ACTION_NONE:
> +		edge = ATMEL_TC_ETRGEDG_NONE;
> +		break;
> +	case ATMEL_TC_SYNAPSE_ACTION_RISING_EDGE:
> +		edge = ATMEL_TC_ETRGEDG_RISING;
> +		break;
> +	case ATMEL_TC_SYNAPSE_ACTION_FALLING_EDGE:
> +		edge = ATMEL_TC_ETRGEDG_FALLING;
> +		break;
> +	case ATMEL_TC_SYNAPSE_ACTION_BOTH_EDGE:
> +		edge = ATMEL_TC_ETRGEDG_BOTH;
> +		break;
> +	}
> +
> +	return regmap_write_bits(priv->regmap,
> +				ATMEL_TC_REG(priv->channel[0], CMR),
> +				ATMEL_TC_ETRGEDG, edge);
> +}
> +
> +static int atmel_tc_count_read(struct counter_device *counter,
> +			       struct counter_count *count,
> +			       unsigned long *val)
> +{
> +	struct atmel_tc_data *const priv = counter->priv;
> +	u32 cnt;
> +
> +	regmap_read(priv->regmap, ATMEL_TC_REG(priv->channel[0], CV), &cnt);
> +	*val = cnt;
> +
> +	return 0;
> +}
> +
> +static struct counter_count atmel_tc_counts[] = {
> +	{
> +		.id = 0,
> +		.name = "Timer Counter",
> +		.functions_list = atmel_tc_count_functions,
> +		.num_functions = ARRAY_SIZE(atmel_tc_count_functions),
> +		.synapses = atmel_tc_count_synapses,
> +		.num_synapses = ARRAY_SIZE(atmel_tc_count_synapses),
> +	},
> +};
> +
> +static struct counter_ops atmel_tc_ops = {
> +	.signal_read  = atmel_tc_count_signal_read,
> +	.count_read   = atmel_tc_count_read,
> +	.function_get = atmel_tc_count_function_get,
> +	.function_set = atmel_tc_count_function_set,
> +	.action_get   = atmel_tc_count_action_get,
> +	.action_set   = atmel_tc_count_action_set
> +};
> +
> +static const struct atmel_tcb_config tcb_rm9200_config = {
> +		.counter_width = 16,
> +};
> +
> +static const struct atmel_tcb_config tcb_sam9x5_config = {
> +		.counter_width = 32,
> +};
> +
> +static const struct atmel_tcb_config tcb_sama5d2_config = {
> +		.counter_width = 32,
> +		.has_gclk = true,
> +		.has_qdec = true,
> +};
> +
> +static const struct atmel_tcb_config tcb_sama5d3_config = {
> +		.counter_width = 32,
> +		.has_qdec = true,
> +};
> +
> +static const struct of_device_id atmel_tc_of_match[] = {
> +	{ .compatible = "atmel,at91rm9200-tcb", .data = &tcb_rm9200_config, },
> +	{ .compatible = "atmel,at91sam9x5-tcb", .data = &tcb_sam9x5_config, },
> +	{ .compatible = "atmel,sama5d2-tcb", .data = &tcb_sama5d2_config, },
> +	{ .compatible = "atmel,sama5d3-tcb", .data = &tcb_sama5d3_config, },
> +	{ /* sentinel */ }
> +};
> +
> +static int atmel_tc_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	const struct atmel_tcb_config *tcb_config;
> +	const struct of_device_id *match;
> +	struct atmel_tc_data *priv;
> +	char clk_name[7];
> +	struct regmap *regmap;
> +	struct clk *clk[3];
> +	int channel;
> +	int ret, i;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	match = of_match_node(atmel_tc_of_match, np->parent);
> +	tcb_config = match->data;
> +	if (!tcb_config) {
> +		dev_err(&pdev->dev, "No matching parent node found\n");
> +		return -ENODEV;
> +	}
> +
> +	regmap = syscon_node_to_regmap(np->parent);
> +	if (IS_ERR(priv->regmap))
> +		return PTR_ERR(priv->regmap);
> +
> +	/* max. channels number is 2 when in QDEC mode */
> +	priv->num_channels = of_property_count_u32_elems(np, "reg");
> +	if (priv->num_channels < 0) {
> +		dev_err(&pdev->dev, "Invalid or missing channel\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Register channels and initialize clocks */
> +	for (i = 0; i < priv->num_channels; i++) {
> +		ret = of_property_read_u32_index(np, "reg", i, &channel);
> +		if (ret < 0 || channel > 2)
> +			return -ENODEV;
> +
> +		priv->channel[i] = channel;
> +
> +		snprintf(clk_name, sizeof(clk_name), "t%d_clk", channel);
> +
> +		clk[i] = of_clk_get_by_name(np->parent, clk_name);
> +		if (IS_ERR(clk[i])) {
> +			/* Fallback to t0_clk */
> +			clk[i] = of_clk_get_by_name(np->parent, "t0_clk");
> +			if (IS_ERR(clk[i]))
> +				return PTR_ERR(clk[i]);
> +		}
> +
> +		ret = clk_prepare_enable(clk[i]);
> +		if (ret)
> +			return ret;
If you see the below, you'll note I mention this not being cleaned up on
remove. 

I would suggest using devm_add_action_or_reset to automate the cleanup
(and let you get rid of the error path below).

> +
> +		dev_info(&pdev->dev,
> +			 "Initialized capture mode on channel %d\n",
> +			 channel);

Isn't this apparent from the resulting counter being created?  I'd argue
that it is therefore noise in the kernel log and demote it to dev_dbg

> +	}
> +
> +	priv->tc_cfg = tcb_config;
> +	priv->regmap = regmap;
> +	priv->counter.name = dev_name(&pdev->dev);
> +	priv->counter.parent = &pdev->dev;
> +	priv->counter.ops = &atmel_tc_ops;
> +	priv->counter.num_counts = ARRAY_SIZE(atmel_tc_counts);
> +	priv->counter.counts = atmel_tc_counts;
> +	priv->counter.num_signals = ARRAY_SIZE(atmel_tc_count_signals);
> +	priv->counter.signals = atmel_tc_count_signals;
> +	priv->counter.priv = priv;
> +
> +	ret = devm_counter_register(&pdev->dev, &priv->counter);

> +	if (ret < 0) {
> +		for (i = 0; i < priv->num_channels; i++)
> +			clk_disable_unprepare(clk[i]);

What does this in the remove path?

I initially thought you'll have a race here because of mixing managed
and unmanaged cleanup (which will be an issue if you do add this to remove
path) but then noticed there was no remove.

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id atmel_tc_dt_ids[] = {
> +	{ .compatible = "atmel,tcb-capture", },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, atmel_tc_dt_ids);
> +
> +static struct platform_driver atmel_tc_driver = {
> +	.probe = atmel_tc_probe,
> +	.driver = {
> +		.name = "atmel-tcb-capture",
> +		.of_match_table = atmel_tc_dt_ids,
> +	},
> +};
> +module_platform_driver(atmel_tc_driver);
> +
> +MODULE_AUTHOR("Kamel Bouhara <[email-masked]>");
> +MODULE_DESCRIPTION("Atmel TCB Capture driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.25.0
> 

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