[PATCH v6 0/4] Fix bugs in kona pwm driver and pwm core

[PATCH v6 0/4] Fix bugs in kona pwm driver and pwm core

[Jonathan Richardson]

This patchset fixes a number of bugs in the Broadcom Kona pwm driver. It also
fixes a bug in the pwm core where the enabled state was incorrect on failed
calls to enable. Also, a new function was added to the pwm core to add pwm chips
with inversed polarity for chips that have a different default polarity than the
core. The prevents incorrect polarity being reported.

These changes are required for the Kona pwm driver to work on Cygnus and the
same pwm IP is being used.

Changes from v5:
  - Address Dmitry's comment on code cleanup of pwm_enable() in pwm core.
  - Including all patches from different contributors in this patchset. Some
	were left out in v4.

Changes from v4:
  - Rebased to Tim Kryger's patch that adds support in pwm core to add driver
    with inversed polarity.
  - Removed patch 2 that resolved difference between hardware default polarity
    and pwm framework default polarity. The default polarity is set properly now
    when the pwm driver is registered with the pwm framework.

Arun Ramamurthy (1):
  drivers: pwm: bcm-kona: Dont set polarity in probe

Jonathan Richardson (2):
  pwm: kona: Fix incorrect config, disable, and polarity procedures
  pwm: core: Set enable state properly on failed call to enable

Tim Kryger (1):
  drivers: pwm: core: Add pwmchip_add_inversed

 drivers/pwm/core.c         |   52 +++++++++++++++++++++------
 drivers/pwm/pwm-bcm-kona.c |   84 +++++++++++++++++++++++++++++++++-----------
 include/linux/pwm.h        |    6 ++++
 3 files changed, 110 insertions(+), 32 deletions(-)

-- 
1.7.9.5

[PATCH v6 1/4] drivers: pwm: core: Add pwmchip_add_inversed

[Jonathan Richardson]

From: Tim Kryger <tim.kryger@gmail.com>

Add a new function to register a PWM chip with channels that have their
initial polarity as inversed.  This benefits drivers of controllers that
by default operate with inversed polarity by removing the need to modify
the polarity during initialization.

Signed-off-by: Tim Kryger <tim.kryger@gmail.com>
Signed-off-by: Jonathan Richardson <jonathar@broadcom.com>
---
 drivers/pwm/core.c  |   36 ++++++++++++++++++++++++++++--------
 include/linux/pwm.h |    6 ++++++
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 810aef3..c0a550b 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -222,14 +222,8 @@ void *pwm_get_chip_data(struct pwm_device *pwm)
 }
 EXPORT_SYMBOL_GPL(pwm_get_chip_data);
 
-/**
- * pwmchip_add() - register a new PWM chip
- * @chip: the PWM chip to add
- *
- * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
- * will be used.
- */
-int pwmchip_add(struct pwm_chip *chip)
+static int pwmchip_add_with_polarity(struct pwm_chip *chip,
+				     enum pwm_polarity polarity)
 {
 	struct pwm_device *pwm;
 	unsigned int i;
@@ -259,6 +253,7 @@ int pwmchip_add(struct pwm_chip *chip)
 		pwm->chip = chip;
 		pwm->pwm = chip->base + i;
 		pwm->hwpwm = i;
+		pwm->polarity = polarity;
 
 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
 	}
@@ -279,9 +274,34 @@ out:
 	mutex_unlock(&pwm_lock);
 	return ret;
 }
+
+/**
+ * pwmchip_add() - register a new PWM chip
+ * @chip: the PWM chip to add
+ *
+ * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
+ * will be used.  The initial polarity for all channels is normal.
+ */
+int pwmchip_add(struct pwm_chip *chip)
+{
+	return pwmchip_add_with_polarity(chip, PWM_POLARITY_NORMAL);
+}
 EXPORT_SYMBOL_GPL(pwmchip_add);
 
 /**
+ * pwmchip_add_inversed() - register a new PWM chip
+ * @chip: the PWM chip to add
+ *
+ * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
+ * will be used.  The initial polarity for all channels is inversed.
+ */
+int pwmchip_add_inversed(struct pwm_chip *chip)
+{
+	return pwmchip_add_with_polarity(chip, PWM_POLARITY_INVERSED);
+}
+EXPORT_SYMBOL_GPL(pwmchip_add_inversed);
+
+/**
  * pwmchip_remove() - remove a PWM chip
  * @chip: the PWM chip to remove
  *
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index e90628c..358547f 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -183,6 +183,7 @@ int pwm_set_chip_data(struct pwm_device *pwm, void *data);
 void *pwm_get_chip_data(struct pwm_device *pwm);
 
 int pwmchip_add(struct pwm_chip *chip);
+int pwmchip_add_inversed(struct pwm_chip *chip);
 int pwmchip_remove(struct pwm_chip *chip);
 struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
 					 unsigned int index,
@@ -217,6 +218,11 @@ static inline int pwmchip_add(struct pwm_chip *chip)
 	return -EINVAL;
 }
 
+static inline int pwmchip_add_inversed(struct pwm_chip *chip)
+{
+	return -EINVAL;
+}
+
 static inline int pwmchip_remove(struct pwm_chip *chip)
 {
 	return -EINVAL;
-- 
1.7.9.5

[PATCH v6 2/4] drivers: pwm: bcm-kona: Dont set polarity in probe

[Jonathan Richardson]

From: Arun Ramamurthy <arunrama@broadcom.com>

Omit setting the polarity to normal during probe and instead use the
new pwmchip_add_inversed function to register a PWM chip with default
polarity of inversed for all channels as this is the actual hardware
default.

Signed-off-by: Arun Ramamurthy <arunrama@broadcom.com>
Reviewed-by: Ray Jui <rjui@broadcom.com>
Signed-off-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Tim Kryger <tim.kryger@gmail.com>
Signed-off-by: Jonathan Richardson <jonathar@broadcom.com>
---
 drivers/pwm/pwm-bcm-kona.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
index 02bc048..32b3ec6 100644
--- a/drivers/pwm/pwm-bcm-kona.c
+++ b/drivers/pwm/pwm-bcm-kona.c
@@ -266,18 +266,15 @@ static int kona_pwmc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	/* Set smooth mode, push/pull, and normal polarity for all channels */
-	for (chan = 0; chan < kp->chip.npwm; chan++) {
-		value |= (1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
+	/* Set push/pull for all channels */
+	for (chan = 0; chan < kp->chip.npwm; chan++)
 		value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan));
-		value |= (1 << PWM_CONTROL_POLARITY_SHIFT(chan));
-	}
 
 	writel(value, kp->base + PWM_CONTROL_OFFSET);
 
 	clk_disable_unprepare(kp->clk);
 
-	ret = pwmchip_add(&kp->chip);
+	ret = pwmchip_add_inversed(&kp->chip);
 	if (ret < 0)
 		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
 
-- 
1.7.9.5

[PATCH v6 3/4] pwm: kona: Fix incorrect config, disable, and polarity procedures

[Jonathan Richardson]

The config procedure didn't follow the spec which periodically resulted
in failing to enable the output signal. This happened one in ten or
twenty attempts. Following the spec and adding a 400ns delay in the
appropriate locations resolves this problem.

The disable procedure now also follows the spec. The old disable
procedure would result in no change in signal when called.

The polarity procedure no longer applies the settings to change the
output signal because it can't be called when the pwm is enabled anyway.
The polarity is only updated in the control register. The correct
polarity will be applied on enable. The old method of applying changes
would result in no signal when the polarity was changed. The new
apply_settings function would fix this problem but it isn't required
anyway.

Reviewed-by: Arun Ramamurthy <arunrama@broadcom.com>
Reviewed-by: Scott Branden <sbranden@broadcom.com>
Tested-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Jonathan Richardson <jonathar@broadcom.com>
---
 drivers/pwm/pwm-bcm-kona.c |   75 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 60 insertions(+), 15 deletions(-)

diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
index 32b3ec6..8a1dfba 100644
--- a/drivers/pwm/pwm-bcm-kona.c
+++ b/drivers/pwm/pwm-bcm-kona.c
@@ -80,15 +80,19 @@ static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
 {
 	unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
 
-	/* Clear trigger bit but set smooth bit to maintain old output */
-	value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
-	value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
-	writel(value, kp->base + PWM_CONTROL_OFFSET);
+	/*
+	 * There must be a min 400ns delay between clearing enable and setting
+	 * it. Failing to do this may result in no PWM signal.
+	 */
+	ndelay(400);
 
 	/* Set trigger bit and clear smooth bit to apply new settings */
 	value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
 	value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
 	writel(value, kp->base + PWM_CONTROL_OFFSET);
+
+	/* PWMOUT_ENABLE must be held high for at least 400 ns. */
+	ndelay(400);
 }
 
 static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
@@ -121,20 +125,56 @@ static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
 		dc = div64_u64(val, div);
 
 		/* If duty_ns or period_ns are not achievable then return */
-		if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
+		if (pc < PERIOD_COUNT_MIN) {
+			dev_warn(chip->dev,
+				"%s: pwm[%d]: period=%d is not achievable, pc=%lu, prescale=%lu\n",
+				__func__, chan, period_ns, pc, prescale);
+			return -EINVAL;
+		}
+
+		/* If duty_ns is not achievable then return */
+		if (dc < DUTY_CYCLE_HIGH_MIN) {
+			if (0 != duty_ns) {
+				dev_warn(chip->dev,
+					"%s: pwm[%d]: duty cycle=%d is not achievable, dc=%lu, prescale=%lu\n",
+					__func__, chan, duty_ns, dc, prescale);
+			}
 			return -EINVAL;
+		}
 
 		/* If pc and dc are in bounds, the calculation is done */
 		if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
 			break;
 
 		/* Otherwise, increase prescale and recalculate pc and dc */
-		if (++prescale > PRESCALE_MAX)
+		if (++prescale > PRESCALE_MAX) {
+			dev_warn(chip->dev,
+				"%s: pwm[%d]: Prescale (=%lu) within max (=%d) for period=%d and duty cycle=%d is not achievable\n",
+				__func__, chan, prescale, PRESCALE_MAX,
+				period_ns, duty_ns);
 			return -EINVAL;
+		}
 	}
 
-	/* If the PWM channel is enabled, write the settings to the HW */
+	dev_dbg(chip->dev, "pwm[%d]: period=%lu, duty_high=%lu, prescale=%lu\n",
+		chan, pc, dc, prescale);
+
+	/*
+	 * Don't apply settings if disabled. The period and duty cycle are
+	 * always calculated above to ensure the new values are
+	 * validated immediately instead of on enable.
+	 */
 	if (test_bit(PWMF_ENABLED, &pwm->flags)) {
+		value = readl(kp->base + PWM_CONTROL_OFFSET);
+
+		/*
+		 * Clear trigger bit but set smooth bit to maintain old
+		 * output.
+		 */
+		value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
+		value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
+		writel(value, kp->base + PWM_CONTROL_OFFSET);
+
 		value = readl(kp->base + PRESCALE_OFFSET);
 		value &= ~PRESCALE_MASK(chan);
 		value |= prescale << PRESCALE_SHIFT(chan);
@@ -173,11 +213,6 @@ static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	writel(value, kp->base + PWM_CONTROL_OFFSET);
 
-	kona_pwmc_apply_settings(kp, chan);
-
-	/* Wait for waveform to settle before gating off the clock */
-	ndelay(400);
-
 	clk_disable_unprepare(kp->clk);
 
 	return 0;
@@ -207,13 +242,23 @@ static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct kona_pwmc *kp = to_kona_pwmc(chip);
 	unsigned int chan = pwm->hwpwm;
+	unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
+
+	/* Set smooth type to 1 and disable */
+	value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
+	value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
+	writel(value, kp->base + PWM_CONTROL_OFFSET);
 
 	/* Simulate a disable by configuring for zero duty */
 	writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
-	kona_pwmc_apply_settings(kp, chan);
+	writel(0, kp->base + PERIOD_COUNT_OFFSET(chan));
 
-	/* Wait for waveform to settle before gating off the clock */
-	ndelay(400);
+	/* Set prescale to 0 for this channel */
+	value = readl(kp->base + PRESCALE_OFFSET);
+	value &= ~PRESCALE_MASK(chan);
+	writel(value, kp->base + PRESCALE_OFFSET);
+
+	kona_pwmc_apply_settings(kp, chan);
 
 	clk_disable_unprepare(kp->clk);
 }
-- 
1.7.9.5

Re: [PATCH v6 3/4] pwm: kona: Fix incorrect config, disable, and polarity procedures

[Tim Kryger]

On Fri, Apr 10, 2015 at 11:58 AM, Jonathan Richardson
<jonathar@broadcom.com> wrote:

> The polarity procedure no longer applies the settings to change the
> output signal because it can't be called when the pwm is enabled anyway.
> The polarity is only updated in the control register. The correct
> polarity will be applied on enable. The old method of applying changes
> would result in no signal when the polarity was changed. The new
> apply_settings function would fix this problem but it isn't required
> anyway.

Why does this bug fix need to alter when polarity changes take effect?

That is an an unrelated change and I don't really agree with it.

>                 /* If duty_ns or period_ns are not achievable then return */
> -               if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
> +               if (pc < PERIOD_COUNT_MIN) {
> +                       dev_warn(chip->dev,
> +                               "%s: pwm[%d]: period=%d is not achievable, pc=%lu, prescale=%lu\n",
> +                               __func__, chan, period_ns, pc, prescale);
> +                       return -EINVAL;
> +               }
> +
> +               /* If duty_ns is not achievable then return */
> +               if (dc < DUTY_CYCLE_HIGH_MIN) {
> +                       if (0 != duty_ns) {
> +                               dev_warn(chip->dev,
> +                                       "%s: pwm[%d]: duty cycle=%d is not achievable, dc=%lu, prescale=%lu\n",
> +                                       __func__, chan, duty_ns, dc, prescale);
> +                       }
>                         return -EINVAL;
> +               }
>
>                 /* If pc and dc are in bounds, the calculation is done */
>                 if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
>                         break;
>
>                 /* Otherwise, increase prescale and recalculate pc and dc */
> -               if (++prescale > PRESCALE_MAX)
> +               if (++prescale > PRESCALE_MAX) {
> +                       dev_warn(chip->dev,
> +                               "%s: pwm[%d]: Prescale (=%lu) within max (=%d) for period=%d and duty cycle=%d is not achievable\n",
> +                               __func__, chan, prescale, PRESCALE_MAX,
> +                               period_ns, duty_ns);
>                         return -EINVAL;
> +               }
>         }

This extra debug output seems helpful but could you put it in its own
commit and keep this focused on fixing the instability you observed?

> +               /*
> +                * Clear trigger bit but set smooth bit to maintain old
> +                * output.
> +                */
> +               value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
> +               value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
> +               writel(value, kp->base + PWM_CONTROL_OFFSET);
> +

The above lines are duplicated below.  Perhaps a function is in order?

> +       /* Set smooth type to 1 and disable */
> +       value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
> +       value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
> +       writel(value, kp->base + PWM_CONTROL_OFFSET);

It seems like the important parts of the fix could be distilled down
to something like this:

diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
index 02bc048..4ff500c 100644
--- a/drivers/pwm/pwm-bcm-kona.c
+++ b/drivers/pwm/pwm-bcm-kona.c
@@ -76,7 +76,8 @@ static inline struct kona_pwmc *to_kona_pwmc(struct
pwm_chip *_chip)
       return container_of(_chip, struct kona_pwmc, chip);
 }

-static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
+static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp,
+                                 unsigned int chan)
 {
       unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);

@@ -85,10 +86,19 @@ static void kona_pwmc_apply_settings(struct
kona_pwmc *kp, unsigned int chan)
       value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
       writel(value, kp->base + PWM_CONTROL_OFFSET);

+      ndelay(400);
+}
+
+static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
+{
+      unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
+
       /* Set trigger bit and clear smooth bit to apply new settings */
       value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
       value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
       writel(value, kp->base + PWM_CONTROL_OFFSET);
+
+      ndelay(400);
 }

 static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
@@ -135,6 +145,8 @@ static int kona_pwmc_config(struct pwm_chip *chip,
struct pwm_device *pwm,

       /* If the PWM channel is enabled, write the settings to the HW */
       if (test_bit(PWMF_ENABLED, &pwm->flags)) {
+            kona_pwmc_prepare_for_settings(kp, chan);
+
             value = readl(kp->base + PRESCALE_OFFSET);
             value &= ~PRESCALE_MASK(chan);
             value |= prescale << PRESCALE_SHIFT(chan);
@@ -164,6 +176,8 @@ static int kona_pwmc_set_polarity(struct pwm_chip
*chip, struct pwm_device *pwm,
             return ret;
       }

+      kona_pwmc_prepare_for_settings(kp, chan);
+
       value = readl(kp->base + PWM_CONTROL_OFFSET);

       if (polarity == PWM_POLARITY_NORMAL)
@@ -175,9 +189,6 @@ static int kona_pwmc_set_polarity(struct pwm_chip
*chip, struct pwm_device *pwm,

       kona_pwmc_apply_settings(kp, chan);

-      /* Wait for waveform to settle before gating off the clock */
-      ndelay(400);
-
       clk_disable_unprepare(kp->clk);

       return 0;
@@ -209,12 +220,10 @@ static void kona_pwmc_disable(struct pwm_chip
*chip, struct pwm_device *pwm)
       unsigned int chan = pwm->hwpwm;

       /* Simulate a disable by configuring for zero duty */
+      kona_pwmc_prepare_for_settings(kp, chan);
       writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
       kona_pwmc_apply_settings(kp, chan);

-      /* Wait for waveform to settle before gating off the clock */
-      ndelay(400);
-
       clk_disable_unprepare(kp->clk);
 }

Re: [PATCH v6 3/4] pwm: kona: Fix incorrect config, disable, and polarity procedures

[Jonathan Richardson]

Tim, just one comment below. All other suggestions will be made for the
next patch set.

On 15-05-06 09:26 PM, Tim Kryger wrote:
> On Fri, Apr 10, 2015 at 11:58 AM, Jonathan Richardson
> <jonathar@broadcom.com> wrote:
> 
>> The polarity procedure no longer applies the settings to change the
>> output signal because it can't be called when the pwm is enabled anyway.
>> The polarity is only updated in the control register. The correct
>> polarity will be applied on enable. The old method of applying changes
>> would result in no signal when the polarity was changed. The new
>> apply_settings function would fix this problem but it isn't required
>> anyway.
> 
> Why does this bug fix need to alter when polarity changes take effect?

The original kona_pwmc_set_polarity() function didn't work on Cygnus
because of the updated kona_pwmc_apply_settings() that we fixed for to
use the updated method received from the chip team. In the process of
fixing it I just took out the apply settings completely because the
polarity can only be changed when the pwm is disabled (from core.c) and
it seemed simpler to just write the polarity to the config register and
let the enable procedure handle the application of polarity when the
signal was actually enabled. I didn't see the point of trying to apply
the polarity when the output signal is disabled. It's the same as
writing the duty cycle and period when the pwm is disabled - the
settings are stored but don't take effect until enabled. I didn't see
any change in signal behaviour by simplifying the polarity function.

> 
> That is an an unrelated change and I don't really agree with it.
> 
>>                 /* If duty_ns or period_ns are not achievable then return */
>> -               if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
>> +               if (pc < PERIOD_COUNT_MIN) {
>> +                       dev_warn(chip->dev,
>> +                               "%s: pwm[%d]: period=%d is not achievable, pc=%lu, prescale=%lu\n",
>> +                               __func__, chan, period_ns, pc, prescale);
>> +                       return -EINVAL;
>> +               }
>> +
>> +               /* If duty_ns is not achievable then return */
>> +               if (dc < DUTY_CYCLE_HIGH_MIN) {
>> +                       if (0 != duty_ns) {
>> +                               dev_warn(chip->dev,
>> +                                       "%s: pwm[%d]: duty cycle=%d is not achievable, dc=%lu, prescale=%lu\n",
>> +                                       __func__, chan, duty_ns, dc, prescale);
>> +                       }
>>                         return -EINVAL;
>> +               }
>>
>>                 /* If pc and dc are in bounds, the calculation is done */
>>                 if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
>>                         break;
>>
>>                 /* Otherwise, increase prescale and recalculate pc and dc */
>> -               if (++prescale > PRESCALE_MAX)
>> +               if (++prescale > PRESCALE_MAX) {
>> +                       dev_warn(chip->dev,
>> +                               "%s: pwm[%d]: Prescale (=%lu) within max (=%d) for period=%d and duty cycle=%d is not achievable\n",
>> +                               __func__, chan, prescale, PRESCALE_MAX,
>> +                               period_ns, duty_ns);
>>                         return -EINVAL;
>> +               }
>>         }
> 
> This extra debug output seems helpful but could you put it in its own
> commit and keep this focused on fixing the instability you observed?
> 
>> +               /*
>> +                * Clear trigger bit but set smooth bit to maintain old
>> +                * output.
>> +                */
>> +               value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
>> +               value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
>> +               writel(value, kp->base + PWM_CONTROL_OFFSET);
>> +
> 
> The above lines are duplicated below.  Perhaps a function is in order?
> 
>> +       /* Set smooth type to 1 and disable */
>> +       value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
>> +       value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
>> +       writel(value, kp->base + PWM_CONTROL_OFFSET);
> 
> It seems like the important parts of the fix could be distilled down
> to something like this:
> 
> diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
> index 02bc048..4ff500c 100644
> --- a/drivers/pwm/pwm-bcm-kona.c
> +++ b/drivers/pwm/pwm-bcm-kona.c
> @@ -76,7 +76,8 @@ static inline struct kona_pwmc *to_kona_pwmc(struct
> pwm_chip *_chip)
>        return container_of(_chip, struct kona_pwmc, chip);
>  }
> 
> -static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
> +static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp,
> +                                 unsigned int chan)
>  {
>        unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
> 
> @@ -85,10 +86,19 @@ static void kona_pwmc_apply_settings(struct
> kona_pwmc *kp, unsigned int chan)
>        value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
>        writel(value, kp->base + PWM_CONTROL_OFFSET);
> 
> +      ndelay(400);
> +}
> +
> +static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
> +{
> +      unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
> +
>        /* Set trigger bit and clear smooth bit to apply new settings */
>        value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
>        value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
>        writel(value, kp->base + PWM_CONTROL_OFFSET);
> +
> +      ndelay(400);
>  }
> 
>  static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
> @@ -135,6 +145,8 @@ static int kona_pwmc_config(struct pwm_chip *chip,
> struct pwm_device *pwm,
> 
>        /* If the PWM channel is enabled, write the settings to the HW */
>        if (test_bit(PWMF_ENABLED, &pwm->flags)) {
> +            kona_pwmc_prepare_for_settings(kp, chan);
> +
>              value = readl(kp->base + PRESCALE_OFFSET);
>              value &= ~PRESCALE_MASK(chan);
>              value |= prescale << PRESCALE_SHIFT(chan);
> @@ -164,6 +176,8 @@ static int kona_pwmc_set_polarity(struct pwm_chip
> *chip, struct pwm_device *pwm,
>              return ret;
>        }
> 
> +      kona_pwmc_prepare_for_settings(kp, chan);
> +
>        value = readl(kp->base + PWM_CONTROL_OFFSET);
> 
>        if (polarity == PWM_POLARITY_NORMAL)
> @@ -175,9 +189,6 @@ static int kona_pwmc_set_polarity(struct pwm_chip
> *chip, struct pwm_device *pwm,
> 
>        kona_pwmc_apply_settings(kp, chan);
> 
> -      /* Wait for waveform to settle before gating off the clock */
> -      ndelay(400);
> -
>        clk_disable_unprepare(kp->clk);
> 
>        return 0;
> @@ -209,12 +220,10 @@ static void kona_pwmc_disable(struct pwm_chip
> *chip, struct pwm_device *pwm)
>        unsigned int chan = pwm->hwpwm;
> 
>        /* Simulate a disable by configuring for zero duty */
> +      kona_pwmc_prepare_for_settings(kp, chan);
>        writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
>        kona_pwmc_apply_settings(kp, chan);
> 
> -      /* Wait for waveform to settle before gating off the clock */
> -      ndelay(400);
> -
>        clk_disable_unprepare(kp->clk);
>  }
> 

[PATCH v6 4/4] pwm: core: Set enable state properly on failed call to enable

[Jonathan Richardson]

The pwm_enable function didn't clear the enabled bit if a call to a
clients enable function returned an error. The result was that the state
of the pwm core was wrong. Clearing the bit when enable returns an error
ensures the state is properly set.

Tested-by: Jonathan Richardson <jonathar@broadcom.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jonathan Richardson <jonathar@broadcom.com>
---
 drivers/pwm/core.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index c0a550b..793add5 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -477,10 +477,20 @@ EXPORT_SYMBOL_GPL(pwm_set_polarity);
  */
 int pwm_enable(struct pwm_device *pwm)
 {
-	if (pwm && !test_and_set_bit(PWMF_ENABLED, &pwm->flags))
-		return pwm->chip->ops->enable(pwm->chip, pwm);
+	int err;
+
+	if (!pwm)
+		return -EINVAL;
+
+	if (!test_and_set_bit(PWMF_ENABLED, &pwm->flags)) {
+		err = pwm->chip->ops->enable(pwm->chip, pwm);
+		if (err) {
+			clear_bit(PWMF_ENABLED, &pwm->flags);
+			return err;
+		}
+	}
 
-	return pwm ? 0 : -EINVAL;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(pwm_enable);
 
-- 
1.7.9.5

Re: [PATCH v6 0/4] Fix bugs in kona pwm driver and pwm core

[Scott Branden]

Hi Jonathan,

Patcheset looks good.
Acked-by: Scott Branden <sbranden@broadcom.com>


On 15-04-10 11:58 AM, Jonathan Richardson wrote:
> This patchset fixes a number of bugs in the Broadcom Kona pwm driver. It also
> fixes a bug in the pwm core where the enabled state was incorrect on failed
> calls to enable. Also, a new function was added to the pwm core to add pwm chips
> with inversed polarity for chips that have a different default polarity than the
> core. The prevents incorrect polarity being reported.
>
> These changes are required for the Kona pwm driver to work on Cygnus and the
> same pwm IP is being used.
>
> Changes from v5:
>    - Address Dmitry's comment on code cleanup of pwm_enable() in pwm core.
>    - Including all patches from different contributors in this patchset. Some
> 	were left out in v4.
>
> Changes from v4:
>    - Rebased to Tim Kryger's patch that adds support in pwm core to add driver
>      with inversed polarity.
>    - Removed patch 2 that resolved difference between hardware default polarity
>      and pwm framework default polarity. The default polarity is set properly now
>      when the pwm driver is registered with the pwm framework.
>
> Arun Ramamurthy (1):
>    drivers: pwm: bcm-kona: Dont set polarity in probe
>
> Jonathan Richardson (2):
>    pwm: kona: Fix incorrect config, disable, and polarity procedures
>    pwm: core: Set enable state properly on failed call to enable
>
> Tim Kryger (1):
>    drivers: pwm: core: Add pwmchip_add_inversed
>
>   drivers/pwm/core.c         |   52 +++++++++++++++++++++------
>   drivers/pwm/pwm-bcm-kona.c |   84 +++++++++++++++++++++++++++++++++-----------
>   include/linux/pwm.h        |    6 ++++
>   3 files changed, 110 insertions(+), 32 deletions(-)
>

Re: [PATCH v6 0/4] Fix bugs in kona pwm driver and pwm core

[Jonathan Richardson]

Pinging maintainer and others. Could you please let me know when you can
provide feedback on this patchset.

Tim, were you ok with these changes now or do you still have concerns
about changing the driver? I didn't hear back from after our last
conversation. If there are still concerns we could possibly make a new
cygnus pwm driver, though it would be mostly the same as the existing
kona driver. Or add a DT version to the existing driver that has the new
modified behaviour - though I think this would be messy.

Thanks.

On 15-04-10 11:58 AM, Jonathan Richardson wrote:
> This patchset fixes a number of bugs in the Broadcom Kona pwm driver. It also
> fixes a bug in the pwm core where the enabled state was incorrect on failed
> calls to enable. Also, a new function was added to the pwm core to add pwm chips
> with inversed polarity for chips that have a different default polarity than the
> core. The prevents incorrect polarity being reported.
> 
> These changes are required for the Kona pwm driver to work on Cygnus and the
> same pwm IP is being used.
> 
> Changes from v5:
>   - Address Dmitry's comment on code cleanup of pwm_enable() in pwm core.
>   - Including all patches from different contributors in this patchset. Some
> 	were left out in v4.
> 
> Changes from v4:
>   - Rebased to Tim Kryger's patch that adds support in pwm core to add driver
>     with inversed polarity.
>   - Removed patch 2 that resolved difference between hardware default polarity
>     and pwm framework default polarity. The default polarity is set properly now
>     when the pwm driver is registered with the pwm framework.
> 
> Arun Ramamurthy (1):
>   drivers: pwm: bcm-kona: Dont set polarity in probe
> 
> Jonathan Richardson (2):
>   pwm: kona: Fix incorrect config, disable, and polarity procedures
>   pwm: core: Set enable state properly on failed call to enable
> 
> Tim Kryger (1):
>   drivers: pwm: core: Add pwmchip_add_inversed
> 
>  drivers/pwm/core.c         |   52 +++++++++++++++++++++------
>  drivers/pwm/pwm-bcm-kona.c |   84 +++++++++++++++++++++++++++++++++-----------
>  include/linux/pwm.h        |    6 ++++
>  3 files changed, 110 insertions(+), 32 deletions(-)
>