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

Kamel Bouhara
2020-04-15T08:40:59Z

On Sun, Apr 12, 2020 at 11:44:33AM +0100, Jonathan Cameron wrote:
> On Thu, 9 Apr 2020 16:14:01 +0200
> Kamel Bouhara <kamel.bouhara@bootlin.com> 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 <kamel.bouhara@bootlin.com>
> Hi Kamel,
>

Hi Jonathan,

> 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 <kamel.bouhara@bootlin.com>
> > + *
>
> Nitpick. Blank line doesn't add anything :)
>

Fixed, thanks.

> > + */
> > +#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).
>

Alright, thanks for the tip.

> > +
> > + 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
>

Yes it is, thanks.

> > + }
> > +
> > + 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.
>

Fixed.

>
> > + 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 <kamel.bouhara@bootlin.com>");
> > +MODULE_DESCRIPTION("Atmel TCB Capture driver");
> > +MODULE_LICENSE("GPL v2");
> > --
> > 2.25.0
> >
>

--
Kamel Bouhara, Bootlin
Embedded Linux and kernel engineering