Re: [PATCH v2] iio: trigger: stm32-timer: enable clock when in master mode
From: Fabrice Gasnier
Date: Fri Feb 14 2020 - 11:20:12 EST
On 2/14/20 4:14 PM, Jonathan Cameron wrote:
> On Fri, 14 Feb 2020 15:50:57 +0100
> Fabrice Gasnier <fabrice.gasnier@xxxxxx> wrote:
>
>> On 2/14/20 3:20 PM, Jonathan Cameron wrote:
>>> On Fri, 7 Feb 2020 17:30:31 +0100
>>> Fabrice Gasnier <fabrice.gasnier@xxxxxx> wrote:
>>>
>>>> Clock should be enabled as soon as using master modes, even before
>>>> enabling timer. Or, this may provoke bad behavior on the other end
>>>> (slave timer). Then, introduce 'clk_enabled' flag, instead of relying
>>>> on CR1 EN bit, to keep track of clock being enabled (balanced refcount).
>>>> Propagate this anywhere else in the driver.
>>>>
>>>> Also add 'remove' routine to stop timer and disable clock in case it
>>>> has been left enabled. Enforce the user interface has been unregistered
>>>> in the remove routine, before disabling the hardware to avoid possible
>>>> race. So, remove use of devm_ variant to register triggers and unregister
>>>> them before the hardware gets disabled [1].
>>>> [1] https://patchwork.kernel.org/patch/9956247/
>>>>
>>>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
>>> Patch looks fine. So is this a fix for a known issue or a theoretical one?
>>> Just a question of whether to line it up for an rc, or wait for next
>>> merge window. Ideally please give me a fixes tag as well if this
>>> fixes a problem that is being seen in the wild.
>>
>> Hi Jonathan,
>>
>> I got no complain for now. So I think this is fine to wait for the next
>> merge window.
> Hi Fabrice,
>
> Great. Unfortunately this has crossed with other changes on the driver.
> Would you mind doing a rebase on my testing branch? It looked fairly
> simple but I wasn't totally confident to do it without being able
> to test!
Yes, I'll do this shortly ;-)
Thanks,
Fabrice
>
> Thanks,
>
> Jonathan
>
>>
>> Thanks,
>> Fabrice
>>
>>>
>>> Thanks,
>>>
>>> Jonathan
>>>
>>>> ---
>>>> Changes in v2:
>>>> - enforce the user interface has been unregistered in the remove routine,
>>>> before disabling the hardware to avoid possible race.
>>>> ---
>>>> drivers/iio/trigger/stm32-timer-trigger.c | 98 ++++++++++++++++++++++++-------
>>>> 1 file changed, 76 insertions(+), 22 deletions(-)
>>>>
>>>> diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
>>>> index a5dfe65..473853e 100644
>>>> --- a/drivers/iio/trigger/stm32-timer-trigger.c
>>>> +++ b/drivers/iio/trigger/stm32-timer-trigger.c
>>>> @@ -79,10 +79,13 @@ struct stm32_timer_trigger {
>>>> struct device *dev;
>>>> struct regmap *regmap;
>>>> struct clk *clk;
>>>> + bool clk_enabled;
>>>> u32 max_arr;
>>>> const void *triggers;
>>>> const void *valids;
>>>> bool has_trgo2;
>>>> + struct mutex lock; /* concurrent sysfs configuration */
>>>> + struct list_head tr_list;
>>>> };
>>>>
>>>> struct stm32_timer_trigger_cfg {
>>>> @@ -106,7 +109,7 @@ static int stm32_timer_start(struct stm32_timer_trigger *priv,
>>>> {
>>>> unsigned long long prd, div;
>>>> int prescaler = 0;
>>>> - u32 ccer, cr1;
>>>> + u32 ccer;
>>>>
>>>> /* Period and prescaler values depends of clock rate */
>>>> div = (unsigned long long)clk_get_rate(priv->clk);
>>>> @@ -136,9 +139,11 @@ static int stm32_timer_start(struct stm32_timer_trigger *priv,
>>>> if (ccer & TIM_CCER_CCXE)
>>>> return -EBUSY;
>>>>
>>>> - regmap_read(priv->regmap, TIM_CR1, &cr1);
>>>> - if (!(cr1 & TIM_CR1_CEN))
>>>> + mutex_lock(&priv->lock);
>>>> + if (!priv->clk_enabled) {
>>>> + priv->clk_enabled = true;
>>>> clk_enable(priv->clk);
>>>> + }
>>>>
>>>> regmap_write(priv->regmap, TIM_PSC, prescaler);
>>>> regmap_write(priv->regmap, TIM_ARR, prd - 1);
>>>> @@ -157,22 +162,20 @@ static int stm32_timer_start(struct stm32_timer_trigger *priv,
>>>>
>>>> /* Enable controller */
>>>> regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, TIM_CR1_CEN);
>>>> + mutex_unlock(&priv->lock);
>>>>
>>>> return 0;
>>>> }
>>>>
>>>> static void stm32_timer_stop(struct stm32_timer_trigger *priv)
>>>> {
>>>> - u32 ccer, cr1;
>>>> + u32 ccer;
>>>>
>>>> regmap_read(priv->regmap, TIM_CCER, &ccer);
>>>> if (ccer & TIM_CCER_CCXE)
>>>> return;
>>>>
>>>> - regmap_read(priv->regmap, TIM_CR1, &cr1);
>>>> - if (cr1 & TIM_CR1_CEN)
>>>> - clk_disable(priv->clk);
>>>> -
>>>> + mutex_lock(&priv->lock);
>>>> /* Stop timer */
>>>> regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
>>>> regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
>>>> @@ -181,6 +184,12 @@ static void stm32_timer_stop(struct stm32_timer_trigger *priv)
>>>>
>>>> /* Make sure that registers are updated */
>>>> regmap_update_bits(priv->regmap, TIM_EGR, TIM_EGR_UG, TIM_EGR_UG);
>>>> +
>>>> + if (priv->clk_enabled) {
>>>> + priv->clk_enabled = false;
>>>> + clk_disable(priv->clk);
>>>> + }
>>>> + mutex_unlock(&priv->lock);
>>>> }
>>>>
>>>> static ssize_t stm32_tt_store_frequency(struct device *dev,
>>>> @@ -295,11 +304,18 @@ static ssize_t stm32_tt_store_master_mode(struct device *dev,
>>>> for (i = 0; i <= master_mode_max; i++) {
>>>> if (!strncmp(master_mode_table[i], buf,
>>>> strlen(master_mode_table[i]))) {
>>>> + mutex_lock(&priv->lock);
>>>> + if (!priv->clk_enabled) {
>>>> + /* Clock should be enabled first */
>>>> + priv->clk_enabled = true;
>>>> + clk_enable(priv->clk);
>>>> + }
>>>> regmap_update_bits(priv->regmap, TIM_CR2, mask,
>>>> i << shift);
>>>> /* Make sure that registers are updated */
>>>> regmap_update_bits(priv->regmap, TIM_EGR,
>>>> TIM_EGR_UG, TIM_EGR_UG);
>>>> + mutex_unlock(&priv->lock);
>>>> return len;
>>>> }
>>>> }
>>>> @@ -357,11 +373,21 @@ static const struct attribute_group *stm32_trigger_attr_groups[] = {
>>>> static const struct iio_trigger_ops timer_trigger_ops = {
>>>> };
>>>>
>>>> -static int stm32_setup_iio_triggers(struct stm32_timer_trigger *priv)
>>>> +static void stm32_unregister_iio_triggers(struct stm32_timer_trigger *priv)
>>>> +{
>>>> + struct iio_trigger *tr;
>>>> +
>>>> + list_for_each_entry(tr, &priv->tr_list, alloc_list)
>>>> + iio_trigger_unregister(tr);
>>>> +}
>>>> +
>>>> +static int stm32_register_iio_triggers(struct stm32_timer_trigger *priv)
>>>> {
>>>> int ret;
>>>> const char * const *cur = priv->triggers;
>>>>
>>>> + INIT_LIST_HEAD(&priv->tr_list);
>>>> +
>>>> while (cur && *cur) {
>>>> struct iio_trigger *trig;
>>>> bool cur_is_trgo = stm32_timer_is_trgo_name(*cur);
>>>> @@ -388,9 +414,13 @@ static int stm32_setup_iio_triggers(struct stm32_timer_trigger *priv)
>>>>
>>>> iio_trigger_set_drvdata(trig, priv);
>>>>
>>>> - ret = devm_iio_trigger_register(priv->dev, trig);
>>>> - if (ret)
>>>> + ret = iio_trigger_register(trig);
>>>> + if (ret) {
>>>> + stm32_unregister_iio_triggers(priv);
>>>> return ret;
>>>> + }
>>>> +
>>>> + list_add_tail(&trig->alloc_list, &priv->tr_list);
>>>> cur++;
>>>> }
>>>>
>>>> @@ -437,7 +467,6 @@ static int stm32_counter_write_raw(struct iio_dev *indio_dev,
>>>> int val, int val2, long mask)
>>>> {
>>>> struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> - u32 dat;
>>>>
>>>> switch (mask) {
>>>> case IIO_CHAN_INFO_RAW:
>>>> @@ -448,19 +477,23 @@ static int stm32_counter_write_raw(struct iio_dev *indio_dev,
>>>> return -EINVAL;
>>>>
>>>> case IIO_CHAN_INFO_ENABLE:
>>>> + mutex_lock(&priv->lock);
>>>> if (val) {
>>>> - regmap_read(priv->regmap, TIM_CR1, &dat);
>>>> - if (!(dat & TIM_CR1_CEN))
>>>> + if (!priv->clk_enabled) {
>>>> + priv->clk_enabled = true;
>>>> clk_enable(priv->clk);
>>>> + }
>>>> regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN,
>>>> TIM_CR1_CEN);
>>>> } else {
>>>> - regmap_read(priv->regmap, TIM_CR1, &dat);
>>>> regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN,
>>>> 0);
>>>> - if (dat & TIM_CR1_CEN)
>>>> + if (priv->clk_enabled) {
>>>> + priv->clk_enabled = false;
>>>> clk_disable(priv->clk);
>>>> + }
>>>> }
>>>> + mutex_unlock(&priv->lock);
>>>> return 0;
>>>> }
>>>>
>>>> @@ -556,7 +589,6 @@ static int stm32_set_enable_mode(struct iio_dev *indio_dev,
>>>> {
>>>> struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> int sms = stm32_enable_mode2sms(mode);
>>>> - u32 val;
>>>>
>>>> if (sms < 0)
>>>> return sms;
>>>> @@ -564,11 +596,12 @@ static int stm32_set_enable_mode(struct iio_dev *indio_dev,
>>>> * Triggered mode sets CEN bit automatically by hardware. So, first
>>>> * enable counter clock, so it can use it. Keeps it in sync with CEN.
>>>> */
>>>> - if (sms == 6) {
>>>> - regmap_read(priv->regmap, TIM_CR1, &val);
>>>> - if (!(val & TIM_CR1_CEN))
>>>> - clk_enable(priv->clk);
>>>> + mutex_lock(&priv->lock);
>>>> + if (sms == 6 && !priv->clk_enabled) {
>>>> + clk_enable(priv->clk);
>>>> + priv->clk_enabled = true;
>>>> }
>>>> + mutex_unlock(&priv->lock);
>>>>
>>>> regmap_update_bits(priv->regmap, TIM_SMCR, TIM_SMCR_SMS, sms);
>>>>
>>>> @@ -752,8 +785,9 @@ static int stm32_timer_trigger_probe(struct platform_device *pdev)
>>>> priv->triggers = triggers_table[index];
>>>> priv->valids = cfg->valids_table[index];
>>>> stm32_timer_detect_trgo2(priv);
>>>> + mutex_init(&priv->lock);
>>>>
>>>> - ret = stm32_setup_iio_triggers(priv);
>>>> + ret = stm32_register_iio_triggers(priv);
>>>> if (ret)
>>>> return ret;
>>>>
>>>> @@ -762,6 +796,25 @@ static int stm32_timer_trigger_probe(struct platform_device *pdev)
>>>> return 0;
>>>> }
>>>>
>>>> +static int stm32_timer_trigger_remove(struct platform_device *pdev)
>>>> +{
>>>> + struct stm32_timer_trigger *priv = platform_get_drvdata(pdev);
>>>> + u32 val;
>>>> +
>>>> + /* Unregister triggers before everything can be safely turned off */
>>>> + stm32_unregister_iio_triggers(priv);
>>>> +
>>>> + /* Check if nobody else use the timer, then disable it */
>>>> + regmap_read(priv->regmap, TIM_CCER, &val);
>>>> + if (!(val & TIM_CCER_CCXE))
>>>> + regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
>>>> +
>>>> + if (priv->clk_enabled)
>>>> + clk_disable(priv->clk);
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> static const struct stm32_timer_trigger_cfg stm32_timer_trg_cfg = {
>>>> .valids_table = valids_table,
>>>> .num_valids_table = ARRAY_SIZE(valids_table),
>>>> @@ -786,6 +839,7 @@ MODULE_DEVICE_TABLE(of, stm32_trig_of_match);
>>>>
>>>> static struct platform_driver stm32_timer_trigger_driver = {
>>>> .probe = stm32_timer_trigger_probe,
>>>> + .remove = stm32_timer_trigger_remove,
>>>> .driver = {
>>>> .name = "stm32-timer-trigger",
>>>> .of_match_table = stm32_trig_of_match,
>>>
>