[PATCH v10 00/17] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API

[PATCH v10 00/17] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API

[Hans de Goede]

Hi All,

Here is hopefully the last version of this series, as everything seems
to be ready for merging this now.

The only difference from v9 is correcting some mistakes in the commit-msg of:
[PATCH v10 06/17] pwm: lpss: Make pwm_lpss_apply() not rely on hardware state

I plan is to push the entire series to drm-intel-next-queued
(because of interdependencies) once the series has passed CI.

This series has been tested (and re-tested after adding various bug-fixes)
extensively. It has been tested on the following devices:

-Asus T100TA  BYT + CRC-PMIC PWM
-Toshiba WT8-A  BYT + CRC-PMIC PWM
-Thundersoft TS178  BYT + CRC-PMIC PWM, inverse PWM
-Asus T100HA  CHT + CRC-PMIC PWM
-Terra Pad 1061  BYT + LPSS PWM
-Trekstor Twin 10.1  BYT + LPSS PWM
-Asus T101HA  CHT + LPSS PWM
-GPD Pocket  CHT + LPSS PWM
-Acer One S1003  CHT + LPSS PWM

Regards,

Hans


Changelog:

Changes in v10:
- Fixup the commit msg of:
  [PATCH v10 06/17] pwm: lpss: Make pwm_lpss_apply() not rely on hardware state

Changes in v9:
- Replace:
  [PATCH v8 06/17] pwm: lpss: Use pwm_lpss_restore() when restoring state on resume
  [PATCH v8 07/17] pwm: lpss: Always update state and set update bit
  with:
  [PATCH v9 06/17] pwm: lpss: Make pwm_lpss_apply() not rely on hardware state
  [PATCH v9 07/17] pwm: lpss: Remove suspend/resume handlers

Changes in v8:
- Add a new patch dealing with the ACPI/DSDT GFX0._PS3 code poking the PWM controller
  in unexpected ways on some Cherry Trail devices

Changes in v7:
- Fix a u64 divide leading to undefined reference to `__udivdi3' errors on 32 bit
  platforms by casting the divisor to an unsigned long

Changes in v6:
- Rebase on v5.9-rc1
- Adjust pwm-crc patches for pwm_state.period and .duty_cycle now being u64

Changes in v5:
- Dropped the "pwm: lpss: Correct get_state result for base_unit == 0"
  patch. The base_unit == 0 condition should never happen and sofar it is
  unclear what the proper behavior / correct values to store in the
  pwm_state should be when this does happen.  Since this patch was added as
  an extra pwm-lpss fix in v4 of this patch-set and otherwise is orthogonal
  to the of this patch-set just drop it (again).
- "[PATCH 04/16] pwm: lpss: Add range limit check for the base_unit register value"
  - Use clamp_val(... instead of clam_t(unsigned long long, ...
- "[PATCH 05/16] pwm: lpss: Add pwm_lpss_prepare_enable() helper"
  - This is a new patch in v5 of this patchset
- [PATCH 06/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume
  - Use the new pwm_lpss_prepare_enable() helper

Changes in v4:
- "[PATCH v4 06/16] pwm: lpss: Correct get_state result for base_unit == 0"
  - This is a new patch in v4 of this patchset
- "[PATCH v4 12/16] pwm: crc: Implement get_state() method"
  - Use DIV_ROUND_UP when calculating the period and duty_cycle values
- "[PATCH v4 16/16] drm/i915: panel: Use atomic PWM API for devs with an external PWM controller"
  - Add a note to the commit message about the changes in pwm_disable_backlight()
  - Use the pwm_set/get_relative_duty_cycle() helpers

Changes in v3:
- "[PATCH v3 04/15] pwm: lpss: Add range limit check for the base_unit register value"
  - Use base_unit_range - 1 as maximum value for the clamp()
- "[PATCH v3 05/15] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume"
  - This replaces the "pwm: lpss: Set SW_UPDATE bit when enabling the PWM"
    patch from previous versions of this patch-set, which really was a hack
    working around the resume issue which this patch fixes properly.
- PATCH v3 6 - 11 pwm-crc changes:
  - Various small changes resulting from the reviews by Andy and Uwe,
    including some refactoring of the patches to reduce the amount of churn
    in the patch-set

Changes in v2:
- Fix coverletter subject
- Drop accidentally included debugging patch
- "[PATCH v3 02/15] ACPI / LPSS: Save Cherry Trail PWM ctx registers only once (
  - Move #define LPSS_SAVE_CTX_ONCE define to group it with LPSS_SAVE_CTX

[PATCH v10 01/17] ACPI / LPSS: Resume Cherry Trail PWM controller in no-irq phase

[Hans de Goede]

The DSDTs on most Cherry Trail devices have an ugly clutch where the PWM
controller gets poked from the _PS0 method of the graphics-card device:

	Local0 = PSAT /* \_SB_.PCI0.GFX0.PSAT */
	If (((Local0 & 0x03) == 0x03))
	{
	    PSAT &= 0xFFFFFFFC
	    Local1 = PSAT /* \_SB_.PCI0.GFX0.PSAT */
	    RSTA = Zero
	    RSTF = Zero
	    RSTA = One
	    RSTF = One
	    PWMB |= 0xC0000000
	    PWMC = PWMB /* \_SB_.PCI0.GFX0.PWMB */
	}

Where PSAT is the power-status register of the PWM controller, so if it
is in D3 when the GFX0 device's PS0 method runs then it will turn it on
and restore the PWM ctrl register value it saved from its PS3 handler.
Note not only does it restore it, it ors it with 0xC0000000 turning it
on at a time where we may not want it to get turned on at all.

The pwm_get call which the i915 driver does to get a reference to the
PWM controller, already adds a device-link making the GFX0 device a
consumer of the PWM device. So it should already have been resumed when
the above AML runs and the AML should thus not do its undesirable poking
of the PWM controller register.

But the PCI core powers on PCI devices in the no-irq resume phase and
thus calls the troublesome PS0 method in the no-irq resume phase.
Where as LPSS devices by default are resumed in the early resume phase.

This commit sets the resume_from_noirq flag in the bsw_pwm_dev_desc
struct, so that Cherry Trail PWM controllers will be resumed in the
no-irq phase. Together with the device-link added by the pwm-get this
ensures that the PWM controller will be on when the troublesome PS0
method runs, which stops it from poking the PWM controller.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/acpi/acpi_lpss.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
index 5e2bfbcf526f..67892fc0b822 100644
--- a/drivers/acpi/acpi_lpss.c
+++ b/drivers/acpi/acpi_lpss.c
@@ -257,6 +257,7 @@ static const struct lpss_device_desc bsw_pwm_dev_desc = {
 	.flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
 	.prv_offset = 0x800,
 	.setup = bsw_pwm_setup,
+	.resume_from_noirq = true,
 };
 
 static const struct lpss_device_desc byt_uart_dev_desc = {
-- 
2.28.0

[PATCH v10 02/17] ACPI / LPSS: Save Cherry Trail PWM ctx registers only once (at activation)

[Hans de Goede]

The DSDTs on most Cherry Trail devices have an ugly clutch where the PWM
controller gets turned off from the _PS3 method of the graphics-card dev:

            Method (_PS3, 0, Serialized)  // _PS3: Power State 3
            {
                ...
                            PWMB = PWMC /* \_SB_.PCI0.GFX0.PWMC */
                            PSAT |= 0x03
                            Local0 = PSAT /* \_SB_.PCI0.GFX0.PSAT */
                ...
            }

Where PSAT is the power-status register of the PWM controller.

Since the i915 driver will do a pwm_get on the pwm device as it uses it to
control the LCD panel backlight, there is a device-link marking the i915
device as a consumer of the pwm device. So that the PWM controller will
always be suspended after the i915 driver suspends (which is the right
thing to do). This causes the above GFX0 PS3 AML code to run before
acpi_lpss.c calls acpi_lpss_save_ctx().

So on these devices the PWM controller will already be off when
acpi_lpss_save_ctx() runs. This causes it to read/save all 1-s (0xffffffff)
as ctx register values.

When these bogus values get restored on resume the PWM controller actually
keeps working, since most bits are reserved, but this does set bit 3 of
the LPSS General purpose register, which for the PWM controller has the
following function: "This bit is re-used to support 32kHz slow mode.
Default is 19.2MHz as PWM source clock".

This causes the clock of the PWM controller to switch from 19.2MHz to
32KHz, which is a slow-down of a factor 600. Surprisingly enough so far
there have been few bug reports about this. This is likely because the
i915 driver was hardcoding the PWM frequency to 46 KHz, which divided
by 600 would result in a PWM frequency of approx. 78 Hz, which mostly
still works fine. There are some bug reports about the LCD backlight
flickering after suspend/resume which are likely caused by this issue.

But with the upcoming patch-series to finally switch the i915 drivers
code for external PWM controllers to use the atomic API and to honor
the PWM frequency specified in the video BIOS (VBT), this becomes a much
bigger problem. On most cases the VBT specifies either 200 Hz or 20
KHz as PWM frequency, which with the mentioned issue ends up being either
1/3 Hz, where the backlight actually visible blinks on and off every 3s,
or in 33 Hz and horrible flickering of the backlight.

There are a number of possible solutions to this problem:

1. Make acpi_lpss_save_ctx() run before GFX0._PS3
 Pro: Clean solution from pov of not medling with save/restore ctx code
 Con: As mentioned the current ordering is the right thing to do
 Con: Requires assymmetry in at what suspend/resume phase we do the save vs
      restore, requiring more suspend/resume ordering hacks in already
      convoluted acpi_lpss.c suspend/resume code.
2. Do some sort of save once mode for the LPSS ctx
 Pro: Reasonably clean
 Con: Needs a new LPSS flag + code changes to handle the flag
3. Detect we have failed to save the ctx registers and do not restore them
 Pro: Not PWM specific, might help with issues on other LPSS devices too
 Con: If we can get away with not restoring the ctx why bother with it at
      all?
4. Do not save the ctx for CHT PWM controllers
 Pro: Clean, as simple as dropping a flag?
 Con: Not so simple as dropping a flag, needs a new flag to ensure that
      we still do lpss_deassert_reset() on device activation.
5. Make the pwm-lpss code fixup the LPSS-context registers
 Pro: Keeps acpi_lpss.c code clean
 Con: Moves knowledge of LPSS-context into the pwm-lpss.c code

1 and 5 both do not seem to be a desirable way forward.

3 and 4 seem ok, but they both assume that restoring the LPSS-context
registers is not necessary. I have done a couple of test and those do
show that restoring the LPSS-context indeed does not seem to be necessary
on devices using s2idle suspend (and successfully reaching S0i3). But I
have no hardware to test deep / S3 suspend. So I'm not sure that not
restoring the context is safe.

That leaves solution 2, which is about as simple / clean as 3 and 4,
so this commit fixes the described problem by implementing a new
LPSS_SAVE_CTX_ONCE flag and setting that for the CHT PWM controllers.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
- Move #define LPSS_SAVE_CTX_ONCE define to group it with LPSS_SAVE_CTX
---
 drivers/acpi/acpi_lpss.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
index 67892fc0b822..a8d7d83ac761 100644
--- a/drivers/acpi/acpi_lpss.c
+++ b/drivers/acpi/acpi_lpss.c
@@ -67,7 +67,15 @@ ACPI_MODULE_NAME("acpi_lpss");
 #define LPSS_CLK_DIVIDER		BIT(2)
 #define LPSS_LTR			BIT(3)
 #define LPSS_SAVE_CTX			BIT(4)
-#define LPSS_NO_D3_DELAY		BIT(5)
+/*
+ * For some devices the DSDT AML code for another device turns off the device
+ * before our suspend handler runs, causing us to read/save all 1-s (0xffffffff)
+ * as ctx register values.
+ * Luckily these devices always use the same ctx register values, so we can
+ * work around this by saving the ctx registers once on activation.
+ */
+#define LPSS_SAVE_CTX_ONCE		BIT(5)
+#define LPSS_NO_D3_DELAY		BIT(6)
 
 struct lpss_private_data;
 
@@ -254,7 +262,7 @@ static const struct lpss_device_desc byt_pwm_dev_desc = {
 };
 
 static const struct lpss_device_desc bsw_pwm_dev_desc = {
-	.flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
+	.flags = LPSS_SAVE_CTX_ONCE | LPSS_NO_D3_DELAY,
 	.prv_offset = 0x800,
 	.setup = bsw_pwm_setup,
 	.resume_from_noirq = true,
@@ -885,9 +893,14 @@ static int acpi_lpss_activate(struct device *dev)
 	 * we have to deassert reset line to be sure that ->probe() will
 	 * recognize the device.
 	 */
-	if (pdata->dev_desc->flags & LPSS_SAVE_CTX)
+	if (pdata->dev_desc->flags & (LPSS_SAVE_CTX | LPSS_SAVE_CTX_ONCE))
 		lpss_deassert_reset(pdata);
 
+#ifdef CONFIG_PM
+	if (pdata->dev_desc->flags & LPSS_SAVE_CTX_ONCE)
+		acpi_lpss_save_ctx(dev, pdata);
+#endif
+
 	return 0;
 }
 
@@ -1031,7 +1044,7 @@ static int acpi_lpss_resume(struct device *dev)
 
 	acpi_lpss_d3_to_d0_delay(pdata);
 
-	if (pdata->dev_desc->flags & LPSS_SAVE_CTX)
+	if (pdata->dev_desc->flags & (LPSS_SAVE_CTX | LPSS_SAVE_CTX_ONCE))
 		acpi_lpss_restore_ctx(dev, pdata);
 
 	return 0;
-- 
2.28.0

[PATCH v10 03/17] pwm: lpss: Fix off by one error in base_unit math in pwm_lpss_prepare()

[Hans de Goede]

According to the data-sheet the way the PWM controller works is that
each input clock-cycle the base_unit gets added to a N bit counter and
that counter overflowing determines the PWM output frequency.

So assuming e.g. a 16 bit counter this means that if base_unit is set to 1,
after 65535 input clock-cycles the counter has been increased from 0 to
65535 and it will overflow on the next cycle, so it will overflow after
every 65536 clock cycles and thus the calculations done in
pwm_lpss_prepare() should use 65536 and not 65535.

This commit fixes this. Note this also aligns the calculations in
pwm_lpss_prepare() with those in pwm_lpss_get_state().

Note this effectively reverts commit 684309e5043e ("pwm: lpss: Avoid
potential overflow of base_unit"). The next patch in this series really
fixes the potential overflow of the base_unit value.

Fixes: 684309e5043e ("pwm: lpss: Avoid potential overflow of base_unit")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v3:
- Add Fixes tag
- Add Reviewed-by: Andy Shevchenko tag
---
 drivers/pwm/pwm-lpss.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 9d965ffe66d1..43b1fc634af1 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -93,7 +93,7 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
 	 * The equation is:
 	 * base_unit = round(base_unit_range * freq / c)
 	 */
-	base_unit_range = BIT(lpwm->info->base_unit_bits) - 1;
+	base_unit_range = BIT(lpwm->info->base_unit_bits);
 	freq *= base_unit_range;
 
 	base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
@@ -104,8 +104,8 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
 
 	orig_ctrl = ctrl = pwm_lpss_read(pwm);
 	ctrl &= ~PWM_ON_TIME_DIV_MASK;
-	ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT);
-	base_unit &= base_unit_range;
+	ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
+	base_unit &= (base_unit_range - 1);
 	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
 	ctrl |= on_time_div;
 
-- 
2.28.0

[PATCH v10 04/17] pwm: lpss: Add range limit check for the base_unit register value

[Hans de Goede]

When the user requests a high enough period ns value, then the
calculations in pwm_lpss_prepare() might result in a base_unit value of 0.

But according to the data-sheet the way the PWM controller works is that
each input clock-cycle the base_unit gets added to a N bit counter and
that counter overflowing determines the PWM output frequency. Adding 0
to the counter is a no-op. The data-sheet even explicitly states that
writing 0 to the base_unit bits will result in the PWM outputting a
continuous 0 signal.

When the user requestes a low enough period ns value, then the
calculations in pwm_lpss_prepare() might result in a base_unit value
which is bigger then base_unit_range - 1. Currently the codes for this
deals with this by applying a mask:

	base_unit &= (base_unit_range - 1);

But this means that we let the value overflow the range, we throw away the
higher bits and store whatever value is left in the lower bits into the
register leading to a random output frequency, rather then clamping the
output frequency to the highest frequency which the hardware can do.

This commit fixes both issues by clamping the base_unit value to be
between 1 and (base_unit_range - 1).

Fixes: 684309e5043e ("pwm: lpss: Avoid potential overflow of base_unit")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v5:
- Use clamp_val(... instead of clam_t(unsigned long long, ...

Changes in v3:
- Change upper limit of clamp to (base_unit_range - 1)
- Add Fixes tag
---
 drivers/pwm/pwm-lpss.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 43b1fc634af1..da9bc3d10104 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -97,6 +97,8 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
 	freq *= base_unit_range;
 
 	base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
+	/* base_unit must not be 0 and we also want to avoid overflowing it */
+	base_unit = clamp_val(base_unit, 1, base_unit_range - 1);
 
 	on_time_div = 255ULL * duty_ns;
 	do_div(on_time_div, period_ns);
@@ -105,7 +107,6 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
 	orig_ctrl = ctrl = pwm_lpss_read(pwm);
 	ctrl &= ~PWM_ON_TIME_DIV_MASK;
 	ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
-	base_unit &= (base_unit_range - 1);
 	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
 	ctrl |= on_time_div;
 
-- 
2.28.0

[PATCH v10 05/17] pwm: lpss: Add pwm_lpss_prepare_enable() helper

[Hans de Goede]

In the not-enabled -> enabled path pwm_lpss_apply() needs to get a
runtime-pm reference; and then on any errors it needs to release it
again.

This leads to somewhat hard to read code. This commit introduces a new
pwm_lpss_prepare_enable() helper and moves all the steps necessary for
the not-enabled -> enabled transition there, so that we can error check
the entire transition in a single place and only have one pm_runtime_put()
on failure call site.

While working on this I noticed that the enabled -> enabled (update
settings) path was quite similar, so I've added an enable parameter to
the new pwm_lpss_prepare_enable() helper, which allows using it in that
path too.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/pwm/pwm-lpss.c | 45 ++++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index da9bc3d10104..8a136ba2a583 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -122,41 +122,48 @@ static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
 		pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
 }
 
+static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
+				   struct pwm_device *pwm,
+				   const struct pwm_state *state,
+				   bool enable)
+{
+	int ret;
+
+	ret = pwm_lpss_is_updating(pwm);
+	if (ret)
+		return ret;
+
+	pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
+	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == false);
+	ret = pwm_lpss_wait_for_update(pwm);
+	if (ret)
+		return ret;
+
+	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == true);
+	return 0;
+}
+
 static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			  const struct pwm_state *state)
 {
 	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
-	int ret;
+	int ret = 0;
 
 	if (state->enabled) {
 		if (!pwm_is_enabled(pwm)) {
 			pm_runtime_get_sync(chip->dev);
-			ret = pwm_lpss_is_updating(pwm);
-			if (ret) {
-				pm_runtime_put(chip->dev);
-				return ret;
-			}
-			pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
-			pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
-			ret = pwm_lpss_wait_for_update(pwm);
-			if (ret) {
+			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true);
+			if (ret)
 				pm_runtime_put(chip->dev);
-				return ret;
-			}
-			pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
 		} else {
-			ret = pwm_lpss_is_updating(pwm);
-			if (ret)
-				return ret;
-			pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
-			return pwm_lpss_wait_for_update(pwm);
+			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, false);
 		}
 	} else if (pwm_is_enabled(pwm)) {
 		pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
 		pm_runtime_put(chip->dev);
 	}
 
-	return 0;
+	return ret;
 }
 
 static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
-- 
2.28.0

[PATCH v10 06/17] pwm: lpss: Make pwm_lpss_apply() not rely on existing hardware state

[Hans de Goede]

Before this commit pwm_lpss_apply() was assuming 2 pre-conditions
were met by the existing hardware state:

1. That the base-unit and on-time-div read back from the
control register are those actually in use, so that it
can skip setting the update bit if the read-back value
matches the desired values.

2. That the controller is enabled when the cached
pwm_state.enabled says that the controller is enabled.

As the long history of fixes for subtle (often suspend/resume)
lpss-pwm issues shows, these assumptions are not necessary
always true.

1. Specifically is not true on some (*) Cherry Trail devices
with a nasty GFX0._PS3 method which: a. saves the ctrl reg value.
b. sets the base-unit to 0 and writes the update bit to apply/commit
c. restores the original ctrl value without setting the update bit,
so that the 0 base-unit value is still in use.

2. Assumption 2. currently is true, but only because of the code which
saves/restores the state on suspend/resume. By convention restoring the
PWM state should be done by the PWM consumer and the presence of this
code in the pmw-lpss driver is a bug. Therefor the save/restore code will
be dropped in the next patch in this series, after which this assumption
also is no longer true.

This commit changes the pwm_lpss_apply() to not make any assumptions about
the state the hardware is in. Instead it makes pwm_lpss_apply() always
fully program the PWM controller, making it much less fragile.

*) Seen on the Acer One 10 S1003, Lenovo Ideapad Miix 310 and 320 models
and various Medion models.

Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v10:
- Fixup some wording / mistakes in the commit message

Changes in v9:
- This is a new patch in v9 of this series
---
 drivers/pwm/pwm-lpss.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 8a136ba2a583..9c5c7217c9b6 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -85,7 +85,7 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
 	unsigned long long on_time_div;
 	unsigned long c = lpwm->info->clk_rate, base_unit_range;
 	unsigned long long base_unit, freq = NSEC_PER_SEC;
-	u32 orig_ctrl, ctrl;
+	u32 ctrl;
 
 	do_div(freq, period_ns);
 
@@ -104,16 +104,14 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
 	do_div(on_time_div, period_ns);
 	on_time_div = 255ULL - on_time_div;
 
-	orig_ctrl = ctrl = pwm_lpss_read(pwm);
+	ctrl = pwm_lpss_read(pwm);
 	ctrl &= ~PWM_ON_TIME_DIV_MASK;
 	ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
 	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
 	ctrl |= on_time_div;
 
-	if (orig_ctrl != ctrl) {
-		pwm_lpss_write(pwm, ctrl);
-		pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE);
-	}
+	pwm_lpss_write(pwm, ctrl);
+	pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE);
 }
 
 static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
@@ -124,8 +122,7 @@ static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
 
 static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
 				   struct pwm_device *pwm,
-				   const struct pwm_state *state,
-				   bool enable)
+				   const struct pwm_state *state)
 {
 	int ret;
 
@@ -134,12 +131,12 @@ static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
 		return ret;
 
 	pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
-	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == false);
+	pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
 	ret = pwm_lpss_wait_for_update(pwm);
 	if (ret)
 		return ret;
 
-	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == true);
+	pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
 	return 0;
 }
 
@@ -152,11 +149,11 @@ static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (state->enabled) {
 		if (!pwm_is_enabled(pwm)) {
 			pm_runtime_get_sync(chip->dev);
-			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true);
+			ret = pwm_lpss_prepare_enable(lpwm, pwm, state);
 			if (ret)
 				pm_runtime_put(chip->dev);
 		} else {
-			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, false);
+			ret = pwm_lpss_prepare_enable(lpwm, pwm, state);
 		}
 	} else if (pwm_is_enabled(pwm)) {
 		pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
-- 
2.28.0

Re: [PATCH v10 06/17] pwm: lpss: Make pwm_lpss_apply() not rely on existing hardware state

[Andy Shevchenko]

On Thu, Sep 03, 2020 at 01:23:26PM +0200, Hans de Goede wrote:
> Before this commit pwm_lpss_apply() was assuming 2 pre-conditions
> were met by the existing hardware state:
> 
> 1. That the base-unit and on-time-div read back from the
> control register are those actually in use, so that it
> can skip setting the update bit if the read-back value
> matches the desired values.
> 
> 2. That the controller is enabled when the cached
> pwm_state.enabled says that the controller is enabled.
> 
> As the long history of fixes for subtle (often suspend/resume)
> lpss-pwm issues shows, these assumptions are not necessary
> always true.
> 
> 1. Specifically is not true on some (*) Cherry Trail devices
> with a nasty GFX0._PS3 method which: a. saves the ctrl reg value.
> b. sets the base-unit to 0 and writes the update bit to apply/commit
> c. restores the original ctrl value without setting the update bit,
> so that the 0 base-unit value is still in use.
> 
> 2. Assumption 2. currently is true, but only because of the code which
> saves/restores the state on suspend/resume. By convention restoring the
> PWM state should be done by the PWM consumer and the presence of this
> code in the pmw-lpss driver is a bug. Therefor the save/restore code will
> be dropped in the next patch in this series, after which this assumption
> also is no longer true.
> 
> This commit changes the pwm_lpss_apply() to not make any assumptions about
> the state the hardware is in. Instead it makes pwm_lpss_apply() always
> fully program the PWM controller, making it much less fragile.
> 
> *) Seen on the Acer One 10 S1003, Lenovo Ideapad Miix 310 and 320 models
> and various Medion models.

Good one!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v10:
> - Fixup some wording / mistakes in the commit message
> 
> Changes in v9:
> - This is a new patch in v9 of this series
> ---
>  drivers/pwm/pwm-lpss.c | 21 +++++++++------------
>  1 file changed, 9 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
> index 8a136ba2a583..9c5c7217c9b6 100644
> --- a/drivers/pwm/pwm-lpss.c
> +++ b/drivers/pwm/pwm-lpss.c
> @@ -85,7 +85,7 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
>  	unsigned long long on_time_div;
>  	unsigned long c = lpwm->info->clk_rate, base_unit_range;
>  	unsigned long long base_unit, freq = NSEC_PER_SEC;
> -	u32 orig_ctrl, ctrl;
> +	u32 ctrl;
>  
>  	do_div(freq, period_ns);
>  
> @@ -104,16 +104,14 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
>  	do_div(on_time_div, period_ns);
>  	on_time_div = 255ULL - on_time_div;
>  
> -	orig_ctrl = ctrl = pwm_lpss_read(pwm);
> +	ctrl = pwm_lpss_read(pwm);
>  	ctrl &= ~PWM_ON_TIME_DIV_MASK;
>  	ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
>  	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
>  	ctrl |= on_time_div;
>  
> -	if (orig_ctrl != ctrl) {
> -		pwm_lpss_write(pwm, ctrl);
> -		pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE);
> -	}
> +	pwm_lpss_write(pwm, ctrl);
> +	pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE);
>  }
>  
>  static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
> @@ -124,8 +122,7 @@ static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
>  
>  static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
>  				   struct pwm_device *pwm,
> -				   const struct pwm_state *state,
> -				   bool enable)
> +				   const struct pwm_state *state)
>  {
>  	int ret;
>  
> @@ -134,12 +131,12 @@ static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
>  		return ret;
>  
>  	pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
> -	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == false);
> +	pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
>  	ret = pwm_lpss_wait_for_update(pwm);
>  	if (ret)
>  		return ret;
>  
> -	pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == true);
> +	pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
>  	return 0;
>  }
>  
> @@ -152,11 +149,11 @@ static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  	if (state->enabled) {
>  		if (!pwm_is_enabled(pwm)) {
>  			pm_runtime_get_sync(chip->dev);
> -			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true);
> +			ret = pwm_lpss_prepare_enable(lpwm, pwm, state);
>  			if (ret)
>  				pm_runtime_put(chip->dev);
>  		} else {
> -			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, false);
> +			ret = pwm_lpss_prepare_enable(lpwm, pwm, state);
>  		}
>  	} else if (pwm_is_enabled(pwm)) {
>  		pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
> -- 
> 2.28.0
> 

-- 
With Best Regards,
Andy Shevchenko

[PATCH v10 07/17] pwm: lpss: Remove suspend/resume handlers

[Hans de Goede]

PWM controller drivers should not restore the PWM state on resume. The
convention is that PWM consumers do this by calling pwm_apply_state(),
so that it can be done at the exact moment when the consumer needs
the state to be stored, avoiding e.g. backlight flickering.

The only in kernel consumers of the pwm-lpss code, the i915 driver
and the pwm-class sysfs interface code both correctly restore the
state on resume, so there is no need to do this in the pwm-lpss code.

More-over the removed resume handler is buggy, since it blindly
restores the ctrl-register contents without setting the update
bit, which is necessary to get the controller to actually use/apply
the restored base-unit and on-time-div values.

Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v9:
- This is a new patch in v9 of this series
---
 drivers/pwm/pwm-lpss-platform.c |  1 -
 drivers/pwm/pwm-lpss.c          | 24 ------------------------
 drivers/pwm/pwm-lpss.h          |  3 ---
 3 files changed, 28 deletions(-)

diff --git a/drivers/pwm/pwm-lpss-platform.c b/drivers/pwm/pwm-lpss-platform.c
index 48f34d20aecd..c6502cf7a7af 100644
--- a/drivers/pwm/pwm-lpss-platform.c
+++ b/drivers/pwm/pwm-lpss-platform.c
@@ -89,7 +89,6 @@ static int pwm_lpss_prepare(struct device *dev)
 
 static const struct dev_pm_ops pwm_lpss_platform_pm_ops = {
 	.prepare = pwm_lpss_prepare,
-	SET_SYSTEM_SLEEP_PM_OPS(pwm_lpss_suspend, pwm_lpss_resume)
 };
 
 static const struct acpi_device_id pwm_lpss_acpi_match[] = {
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 9c5c7217c9b6..3444c56b4bed 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -260,30 +260,6 @@ int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
 }
 EXPORT_SYMBOL_GPL(pwm_lpss_remove);
 
-int pwm_lpss_suspend(struct device *dev)
-{
-	struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
-	int i;
-
-	for (i = 0; i < lpwm->info->npwm; i++)
-		lpwm->saved_ctrl[i] = readl(lpwm->regs + i * PWM_SIZE + PWM);
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(pwm_lpss_suspend);
-
-int pwm_lpss_resume(struct device *dev)
-{
-	struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
-	int i;
-
-	for (i = 0; i < lpwm->info->npwm; i++)
-		writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM);
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(pwm_lpss_resume);
-
 MODULE_DESCRIPTION("PWM driver for Intel LPSS");
 MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/pwm/pwm-lpss.h b/drivers/pwm/pwm-lpss.h
index 7909fa12fca2..70db7e389d66 100644
--- a/drivers/pwm/pwm-lpss.h
+++ b/drivers/pwm/pwm-lpss.h
@@ -19,7 +19,6 @@ struct pwm_lpss_chip {
 	struct pwm_chip chip;
 	void __iomem *regs;
 	const struct pwm_lpss_boardinfo *info;
-	u32 saved_ctrl[MAX_PWMS];
 };
 
 struct pwm_lpss_boardinfo {
@@ -37,7 +36,5 @@ struct pwm_lpss_boardinfo {
 struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
 				     const struct pwm_lpss_boardinfo *info);
 int pwm_lpss_remove(struct pwm_lpss_chip *lpwm);
-int pwm_lpss_suspend(struct device *dev);
-int pwm_lpss_resume(struct device *dev);
 
 #endif	/* __PWM_LPSS_H */
-- 
2.28.0

Re: [PATCH v10 07/17] pwm: lpss: Remove suspend/resume handlers

[Andy Shevchenko]

On Thu, Sep 03, 2020 at 01:23:27PM +0200, Hans de Goede wrote:
> PWM controller drivers should not restore the PWM state on resume. The
> convention is that PWM consumers do this by calling pwm_apply_state(),
> so that it can be done at the exact moment when the consumer needs
> the state to be stored, avoiding e.g. backlight flickering.
> 
> The only in kernel consumers of the pwm-lpss code, the i915 driver
> and the pwm-class sysfs interface code both correctly restore the
> state on resume, so there is no need to do this in the pwm-lpss code.
> 
> More-over the removed resume handler is buggy, since it blindly
> restores the ctrl-register contents without setting the update
> bit, which is necessary to get the controller to actually use/apply
> the restored base-unit and on-time-div values.

While this is okay

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

the question is do we need to have similar in acpi_lpss.c?
For example,
	static const struct lpss_device_desc byt_pwm_dev_desc = {
		.flags = LPSS_SAVE_CTX,
		^^^^^^^^^^^^^^
		.prv_offset = 0x800,
		.setup = byt_pwm_setup,
	};

	static const struct lpss_device_desc bsw_pwm_dev_desc = {
		.flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
		^^^^^^^^^^^^^^
		.prv_offset = 0x800,
		.setup = bsw_pwm_setup,
	};


> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v9:
> - This is a new patch in v9 of this series
> ---
>  drivers/pwm/pwm-lpss-platform.c |  1 -
>  drivers/pwm/pwm-lpss.c          | 24 ------------------------
>  drivers/pwm/pwm-lpss.h          |  3 ---
>  3 files changed, 28 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-lpss-platform.c b/drivers/pwm/pwm-lpss-platform.c
> index 48f34d20aecd..c6502cf7a7af 100644
> --- a/drivers/pwm/pwm-lpss-platform.c
> +++ b/drivers/pwm/pwm-lpss-platform.c
> @@ -89,7 +89,6 @@ static int pwm_lpss_prepare(struct device *dev)
>  
>  static const struct dev_pm_ops pwm_lpss_platform_pm_ops = {
>  	.prepare = pwm_lpss_prepare,
> -	SET_SYSTEM_SLEEP_PM_OPS(pwm_lpss_suspend, pwm_lpss_resume)
>  };
>  
>  static const struct acpi_device_id pwm_lpss_acpi_match[] = {
> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
> index 9c5c7217c9b6..3444c56b4bed 100644
> --- a/drivers/pwm/pwm-lpss.c
> +++ b/drivers/pwm/pwm-lpss.c
> @@ -260,30 +260,6 @@ int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
>  }
>  EXPORT_SYMBOL_GPL(pwm_lpss_remove);
>  
> -int pwm_lpss_suspend(struct device *dev)
> -{
> -	struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
> -	int i;
> -
> -	for (i = 0; i < lpwm->info->npwm; i++)
> -		lpwm->saved_ctrl[i] = readl(lpwm->regs + i * PWM_SIZE + PWM);
> -
> -	return 0;
> -}
> -EXPORT_SYMBOL_GPL(pwm_lpss_suspend);
> -
> -int pwm_lpss_resume(struct device *dev)
> -{
> -	struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
> -	int i;
> -
> -	for (i = 0; i < lpwm->info->npwm; i++)
> -		writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM);
> -
> -	return 0;
> -}
> -EXPORT_SYMBOL_GPL(pwm_lpss_resume);
> -
>  MODULE_DESCRIPTION("PWM driver for Intel LPSS");
>  MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
>  MODULE_LICENSE("GPL v2");
> diff --git a/drivers/pwm/pwm-lpss.h b/drivers/pwm/pwm-lpss.h
> index 7909fa12fca2..70db7e389d66 100644
> --- a/drivers/pwm/pwm-lpss.h
> +++ b/drivers/pwm/pwm-lpss.h
> @@ -19,7 +19,6 @@ struct pwm_lpss_chip {
>  	struct pwm_chip chip;
>  	void __iomem *regs;
>  	const struct pwm_lpss_boardinfo *info;
> -	u32 saved_ctrl[MAX_PWMS];
>  };
>  
>  struct pwm_lpss_boardinfo {
> @@ -37,7 +36,5 @@ struct pwm_lpss_boardinfo {
>  struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
>  				     const struct pwm_lpss_boardinfo *info);
>  int pwm_lpss_remove(struct pwm_lpss_chip *lpwm);
> -int pwm_lpss_suspend(struct device *dev);
> -int pwm_lpss_resume(struct device *dev);
>  
>  #endif	/* __PWM_LPSS_H */
> -- 
> 2.28.0
> 

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v10 07/17] pwm: lpss: Remove suspend/resume handlers

[Andy Shevchenko]

On Thu, Sep 03, 2020 at 03:48:16PM +0300, Andy Shevchenko wrote:
> On Thu, Sep 03, 2020 at 01:23:27PM +0200, Hans de Goede wrote:

> the question is do we need to have similar in acpi_lpss.c?
> For example,
> 	static const struct lpss_device_desc byt_pwm_dev_desc = {
> 		.flags = LPSS_SAVE_CTX,
> 		^^^^^^^^^^^^^^
> 		.prv_offset = 0x800,
> 		.setup = byt_pwm_setup,
> 	};
> 
> 	static const struct lpss_device_desc bsw_pwm_dev_desc = {
> 		.flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
> 		^^^^^^^^^^^^^^
> 		.prv_offset = 0x800,
> 		.setup = bsw_pwm_setup,
> 	};

Okay, it's a private space which has clock and reset gating, so means we still
need to handle it.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v10 07/17] pwm: lpss: Remove suspend/resume handlers

[Hans de Goede]

Hi,

On 9/3/20 2:56 PM, Andy Shevchenko wrote:
> On Thu, Sep 03, 2020 at 03:48:16PM +0300, Andy Shevchenko wrote:
>> On Thu, Sep 03, 2020 at 01:23:27PM +0200, Hans de Goede wrote:
> 
>> the question is do we need to have similar in acpi_lpss.c?
>> For example,
>> 	static const struct lpss_device_desc byt_pwm_dev_desc = {
>> 		.flags = LPSS_SAVE_CTX,
>> 		^^^^^^^^^^^^^^
>> 		.prv_offset = 0x800,
>> 		.setup = byt_pwm_setup,
>> 	};
>>
>> 	static const struct lpss_device_desc bsw_pwm_dev_desc = {
>> 		.flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY,
>> 		^^^^^^^^^^^^^^
>> 		.prv_offset = 0x800,
>> 		.setup = bsw_pwm_setup,
>> 	};
> 
> Okay, it's a private space which has clock and reset gating, so means we still
> need to handle it.

Right I was about to say the same.

As always, thank you for your reviews.

Regards,

Hans

[PATCH v10 08/17] pwm: crc: Fix period / duty_cycle times being off by a factor of 256

[Hans de Goede]

While looking into adding atomic-pwm support to the pwm-crc driver I
noticed something odd, there is a PWM_BASE_CLK define of 6 MHz and
there is a clock-divider which divides this with a value between 1-128,
and there are 256 duty-cycle steps.

The pwm-crc code before this commit assumed that a clock-divider
setting of 1 means that the PWM output is running at 6 MHZ, if that
is true, where do these 256 duty-cycle steps come from?

This would require an internal frequency of 256 * 6 MHz = 1.5 GHz, that
seems unlikely for a PMIC which is using a silicon process optimized for
power-switching transistors. It is way more likely that there is an 8
bit counter for the duty cycle which acts as an extra fixed divider
wrt the PWM output frequency.

The main user of the pwm-crc driver is the i915 GPU driver which uses it
for backlight control. Lets compare the PWM register values set by the
video-BIOS (the GOP), assuming the extra fixed divider is present versus
the PWM frequency specified in the Video-BIOS-Tables:

Device:		PWM Hz set by BIOS	PWM Hz specified in VBT
Asus T100TA 	200			200
Asus T100HA 	200			200
Lenovo Miix 2 8	23437			20000
Toshiba WT8-A	23437			20000

So as we can see if we assume the extra division by 256 then the register
values set by the GOP are an exact match for the VBT values, where as
otherwise the values would be of by a factor of 256.

This commit fixes the period / duty_cycle calculations to take the
extra division by 256 into account.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v3:
- Use NSEC_PER_USEC instead of adding a new (non-sensical) NSEC_PER_MHZ define
---
 drivers/pwm/pwm-crc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index 272eeb071147..c056eb9b858c 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/drivers/pwm/pwm-crc.c
@@ -21,8 +21,8 @@
 
 #define PWM_MAX_LEVEL		0xFF
 
-#define PWM_BASE_CLK		6000000  /* 6 MHz */
-#define PWM_MAX_PERIOD_NS	21333    /* 46.875KHz */
+#define PWM_BASE_CLK_MHZ	6	/* 6 MHz */
+#define PWM_MAX_PERIOD_NS	5461333	/* 183 Hz */
 
 /**
  * struct crystalcove_pwm - Crystal Cove PWM controller
@@ -72,7 +72,7 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,
 
 		/* changing the clk divisor, need to disable fisrt */
 		crc_pwm_disable(c, pwm);
-		clk_div = PWM_BASE_CLK * period_ns / NSEC_PER_SEC;
+		clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC);
 
 		regmap_write(crc_pwm->regmap, PWM0_CLK_DIV,
 					clk_div | PWM_OUTPUT_ENABLE);
-- 
2.28.0

[PATCH v10 09/17] pwm: crc: Fix off-by-one error in the clock-divider calculations

[Hans de Goede]

The CRC PWM controller has a clock-divider which divides the clock with
a value between 1-128. But as can seen from the PWM_DIV_CLK_xxx
defines, this range maps to a register value of 0-127.

So after calculating the clock-divider we must subtract 1 to get the
register value, unless the requested frequency was so high that the
calculation has already resulted in a (rounded) divider value of 0.

Note that before this fix, setting a period of PWM_MAX_PERIOD_NS which
corresponds to the max. divider value of 128 could have resulted in a
bug where the code would use 128 as divider-register value which would
have resulted in an actual divider value of 0 (and the enable bit being
set). A rounding error stopped this bug from actually happen. This
same rounding error means that after the subtraction of 1 it is impossible
to set the divider to 128. Also bump PWM_MAX_PERIOD_NS by 1 ns to allow
setting a divider of 128 (register-value 127).

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v3:
- Introduce crc_pwm_calc_clk_div() here instead of later in the patch-set
  to reduce the amount of churn in the patch-set a bit
---
 drivers/pwm/pwm-crc.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index c056eb9b858c..44ec7d5b63e1 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/drivers/pwm/pwm-crc.c
@@ -22,7 +22,7 @@
 #define PWM_MAX_LEVEL		0xFF
 
 #define PWM_BASE_CLK_MHZ	6	/* 6 MHz */
-#define PWM_MAX_PERIOD_NS	5461333	/* 183 Hz */
+#define PWM_MAX_PERIOD_NS	5461334	/* 183 Hz */
 
 /**
  * struct crystalcove_pwm - Crystal Cove PWM controller
@@ -39,6 +39,18 @@ static inline struct crystalcove_pwm *to_crc_pwm(struct pwm_chip *pc)
 	return container_of(pc, struct crystalcove_pwm, chip);
 }
 
+static int crc_pwm_calc_clk_div(int period_ns)
+{
+	int clk_div;
+
+	clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC);
+	/* clk_div 1 - 128, maps to register values 0-127 */
+	if (clk_div > 0)
+		clk_div--;
+
+	return clk_div;
+}
+
 static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm)
 {
 	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
@@ -68,11 +80,10 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,
 	}
 
 	if (pwm_get_period(pwm) != period_ns) {
-		int clk_div;
+		int clk_div = crc_pwm_calc_clk_div(period_ns);
 
 		/* changing the clk divisor, need to disable fisrt */
 		crc_pwm_disable(c, pwm);
-		clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC);
 
 		regmap_write(crc_pwm->regmap, PWM0_CLK_DIV,
 					clk_div | PWM_OUTPUT_ENABLE);
-- 
2.28.0

[PATCH v10 10/17] pwm: crc: Fix period changes not having any effect

[Hans de Goede]

The pwm-crc code is using 2 different enable bits:
1. bit 7 of the PWM0_CLK_DIV (PWM_OUTPUT_ENABLE)
2. bit 0 of the BACKLIGHT_EN register

The BACKLIGHT_EN register at address 0x51 really controls a separate
output-only GPIO which is earmarked to be used as output connected to the
backlight-enable pin for LCD panels, this GPO is part of the PMIC's
"Display Panel Control Block." . This pin should probably be moved over
to a GPIO provider driver (and consumers modified accordingly), but that
is something for an(other) patch.

Enabling / disabling the actual PWM output is controlled by the
PWM_OUTPUT_ENABLE bit of the PWM0_CLK_DIV register.

As the comment in the old code already indicates we must disable the PWM
before we can change the clock divider. But the crc_pwm_disable() and
crc_pwm_enable() calls the old code make for this only change the
BACKLIGHT_EN register; and the value of that register does not matter for
changing the period / the divider. What does matter is that the
PWM_OUTPUT_ENABLE bit must be cleared before a new value can be written.

This commit modifies crc_pwm_config() to clear PWM_OUTPUT_ENABLE instead
when changing the period, so that period changes actually work.

Note this fix will cause a significant behavior change on some devices
using the CRC PWM output to drive their backlight. Before the PWM would
always run with the output frequency configured by the BIOS at boot, now
the period time specified by the i915 driver will actually be honored.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/pwm/pwm-crc.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index 44ec7d5b63e1..81232da0c767 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/drivers/pwm/pwm-crc.c
@@ -82,14 +82,11 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,
 	if (pwm_get_period(pwm) != period_ns) {
 		int clk_div = crc_pwm_calc_clk_div(period_ns);
 
-		/* changing the clk divisor, need to disable fisrt */
-		crc_pwm_disable(c, pwm);
+		/* changing the clk divisor, clear PWM_OUTPUT_ENABLE first */
+		regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, 0);
 
 		regmap_write(crc_pwm->regmap, PWM0_CLK_DIV,
 					clk_div | PWM_OUTPUT_ENABLE);
-
-		/* enable back */
-		crc_pwm_enable(c, pwm);
 	}
 
 	/* change the pwm duty cycle */
-- 
2.28.0

[PATCH v10 11/17] pwm: crc: Enable/disable PWM output on enable/disable

[Hans de Goede]

The pwm-crc code is using 2 different enable bits:
1. bit 7 of the PWM0_CLK_DIV (PWM_OUTPUT_ENABLE)
2. bit 0 of the BACKLIGHT_EN register

So far we've kept the PWM_OUTPUT_ENABLE bit set when disabling the PWM,
this commit makes crc_pwm_disable() clear it on disable and makes
crc_pwm_enable() set it again on re-enable.

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v3:
- Remove paragraph about tri-stating the output from the commit message,
  we don't have a datasheet so this was just an unfounded guess
---
 drivers/pwm/pwm-crc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index 81232da0c767..b72008c9b072 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/drivers/pwm/pwm-crc.c
@@ -54,7 +54,9 @@ static int crc_pwm_calc_clk_div(int period_ns)
 static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm)
 {
 	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
+	int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));
 
+	regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div | PWM_OUTPUT_ENABLE);
 	regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1);
 
 	return 0;
@@ -63,8 +65,10 @@ static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm)
 static void crc_pwm_disable(struct pwm_chip *c, struct pwm_device *pwm)
 {
 	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
+	int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));
 
 	regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0);
+	regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div);
 }
 
 static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,
-- 
2.28.0

[PATCH v10 12/17] pwm: crc: Implement apply() method to support the new atomic PWM API

[Hans de Goede]

Replace the enable, disable and config pwm_ops with an apply op,
to support the new atomic PWM API.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v6:
- Rebase on 5.9-rc1
- Use do_div when calculating level because pwm_state.period and .duty_cycle are now u64

Changes in v3:
- Keep crc_pwm_calc_clk_div() helper to avoid needless churn
---
 drivers/pwm/pwm-crc.c | 89 ++++++++++++++++++++++++++-----------------
 1 file changed, 54 insertions(+), 35 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index b72008c9b072..27dc30882424 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/drivers/pwm/pwm-crc.c
@@ -51,59 +51,78 @@ static int crc_pwm_calc_clk_div(int period_ns)
 	return clk_div;
 }
 
-static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm)
+static int crc_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			 const struct pwm_state *state)
 {
-	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
-	int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));
+	struct crystalcove_pwm *crc_pwm = to_crc_pwm(chip);
+	struct device *dev = crc_pwm->chip.dev;
+	int err;
 
-	regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div | PWM_OUTPUT_ENABLE);
-	regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1);
+	if (state->period > PWM_MAX_PERIOD_NS) {
+		dev_err(dev, "un-supported period_ns\n");
+		return -EINVAL;
+	}
 
-	return 0;
-}
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EOPNOTSUPP;
 
-static void crc_pwm_disable(struct pwm_chip *c, struct pwm_device *pwm)
-{
-	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
-	int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));
+	if (pwm_is_enabled(pwm) && !state->enabled) {
+		err = regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0);
+		if (err) {
+			dev_err(dev, "Error writing BACKLIGHT_EN %d\n", err);
+			return err;
+		}
+	}
 
-	regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0);
-	regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div);
-}
+	if (pwm_get_duty_cycle(pwm) != state->duty_cycle ||
+	    pwm_get_period(pwm) != state->period) {
+		u64 level = state->duty_cycle * PWM_MAX_LEVEL;
 
-static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,
-			  int duty_ns, int period_ns)
-{
-	struct crystalcove_pwm *crc_pwm = to_crc_pwm(c);
-	struct device *dev = crc_pwm->chip.dev;
-	int level;
+		do_div(level, state->period);
 
-	if (period_ns > PWM_MAX_PERIOD_NS) {
-		dev_err(dev, "un-supported period_ns\n");
-		return -EINVAL;
+		err = regmap_write(crc_pwm->regmap, PWM0_DUTY_CYCLE, level);
+		if (err) {
+			dev_err(dev, "Error writing PWM0_DUTY_CYCLE %d\n", err);
+			return err;
+		}
 	}
 
-	if (pwm_get_period(pwm) != period_ns) {
-		int clk_div = crc_pwm_calc_clk_div(period_ns);
-
+	if (pwm_is_enabled(pwm) && state->enabled &&
+	    pwm_get_period(pwm) != state->period) {
 		/* changing the clk divisor, clear PWM_OUTPUT_ENABLE first */
-		regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, 0);
+		err = regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, 0);
+		if (err) {
+			dev_err(dev, "Error writing PWM0_CLK_DIV %d\n", err);
+			return err;
+		}
+	}
 
-		regmap_write(crc_pwm->regmap, PWM0_CLK_DIV,
-					clk_div | PWM_OUTPUT_ENABLE);
+	if (pwm_get_period(pwm) != state->period ||
+	    pwm_is_enabled(pwm) != state->enabled) {
+		int clk_div = crc_pwm_calc_clk_div(state->period);
+		int pwm_output_enable = state->enabled ? PWM_OUTPUT_ENABLE : 0;
+
+		err = regmap_write(crc_pwm->regmap, PWM0_CLK_DIV,
+				   clk_div | pwm_output_enable);
+		if (err) {
+			dev_err(dev, "Error writing PWM0_CLK_DIV %d\n", err);
+			return err;
+		}
 	}
 
-	/* change the pwm duty cycle */
-	level = duty_ns * PWM_MAX_LEVEL / period_ns;
-	regmap_write(crc_pwm->regmap, PWM0_DUTY_CYCLE, level);
+	if (!pwm_is_enabled(pwm) && state->enabled) {
+		err = regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1);
+		if (err) {
+			dev_err(dev, "Error writing BACKLIGHT_EN %d\n", err);
+			return err;
+		}
+	}
 
 	return 0;
 }
 
 static const struct pwm_ops crc_pwm_ops = {
-	.config = crc_pwm_config,
-	.enable = crc_pwm_enable,
-	.disable = crc_pwm_disable,
+	.apply = crc_pwm_apply,
 };
 
 static int crystalcove_pwm_probe(struct platform_device *pdev)
-- 
2.28.0

[PATCH v10 13/17] pwm: crc: Implement get_state() method

[Hans de Goede]

Implement the pwm_ops.get_state() method to complete the support for the
new atomic PWM API.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v6:
- Rebase on 5.9-rc1
- Use DIV_ROUND_UP_ULL because pwm_state.period and .duty_cycle are now u64

Changes in v5:
- Fix an indentation issue

Changes in v4:
- Use DIV_ROUND_UP when calculating the period and duty_cycle from the
  controller's register values

Changes in v3:
- Add Andy's Reviewed-by tag
- Remove extra whitespace to align some code after assignments (requested by
  Uwe Kleine-König)
---
 drivers/pwm/pwm-crc.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index 27dc30882424..ecfdfac0c2d9 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/drivers/pwm/pwm-crc.c
@@ -121,8 +121,39 @@ static int crc_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	return 0;
 }
 
+static void crc_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			      struct pwm_state *state)
+{
+	struct crystalcove_pwm *crc_pwm = to_crc_pwm(chip);
+	struct device *dev = crc_pwm->chip.dev;
+	unsigned int clk_div, clk_div_reg, duty_cycle_reg;
+	int error;
+
+	error = regmap_read(crc_pwm->regmap, PWM0_CLK_DIV, &clk_div_reg);
+	if (error) {
+		dev_err(dev, "Error reading PWM0_CLK_DIV %d\n", error);
+		return;
+	}
+
+	error = regmap_read(crc_pwm->regmap, PWM0_DUTY_CYCLE, &duty_cycle_reg);
+	if (error) {
+		dev_err(dev, "Error reading PWM0_DUTY_CYCLE %d\n", error);
+		return;
+	}
+
+	clk_div = (clk_div_reg & ~PWM_OUTPUT_ENABLE) + 1;
+
+	state->period =
+		DIV_ROUND_UP(clk_div * NSEC_PER_USEC * 256, PWM_BASE_CLK_MHZ);
+	state->duty_cycle =
+		DIV_ROUND_UP_ULL(duty_cycle_reg * state->period, PWM_MAX_LEVEL);
+	state->polarity = PWM_POLARITY_NORMAL;
+	state->enabled = !!(clk_div_reg & PWM_OUTPUT_ENABLE);
+}
+
 static const struct pwm_ops crc_pwm_ops = {
 	.apply = crc_pwm_apply,
+	.get_state = crc_pwm_get_state,
 };
 
 static int crystalcove_pwm_probe(struct platform_device *pdev)
-- 
2.28.0

[PATCH v10 14/17] drm/i915: panel: Add get_vbt_pwm_freq() helper

[Hans de Goede]

Factor the code which checks and drm_dbg_kms-s the VBT PWM frequency
out of get_backlight_max_vbt().

This is a preparation patch for honering the VBT PWM frequency for
devices which use an external PWM controller (devices using
pwm_setup_backlight()).

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/gpu/drm/i915/display/intel_panel.c | 27 ++++++++++++++--------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 4072d7062efd..df7472a3b9f8 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -1543,18 +1543,9 @@ static u32 vlv_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
 	return DIV_ROUND_CLOSEST(clock, pwm_freq_hz * mul);
 }
 
-static u32 get_backlight_max_vbt(struct intel_connector *connector)
+static u16 get_vbt_pwm_freq(struct drm_i915_private *dev_priv)
 {
-	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
-	struct intel_panel *panel = &connector->panel;
 	u16 pwm_freq_hz = dev_priv->vbt.backlight.pwm_freq_hz;
-	u32 pwm;
-
-	if (!panel->backlight.hz_to_pwm) {
-		drm_dbg_kms(&dev_priv->drm,
-			    "backlight frequency conversion not supported\n");
-		return 0;
-	}
 
 	if (pwm_freq_hz) {
 		drm_dbg_kms(&dev_priv->drm,
@@ -1567,6 +1558,22 @@ static u32 get_backlight_max_vbt(struct intel_connector *connector)
 			    pwm_freq_hz);
 	}
 
+	return pwm_freq_hz;
+}
+
+static u32 get_backlight_max_vbt(struct intel_connector *connector)
+{
+	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
+	struct intel_panel *panel = &connector->panel;
+	u16 pwm_freq_hz = get_vbt_pwm_freq(dev_priv);
+	u32 pwm;
+
+	if (!panel->backlight.hz_to_pwm) {
+		drm_dbg_kms(&dev_priv->drm,
+			    "backlight frequency conversion not supported\n");
+		return 0;
+	}
+
 	pwm = panel->backlight.hz_to_pwm(connector, pwm_freq_hz);
 	if (!pwm) {
 		drm_dbg_kms(&dev_priv->drm,
-- 
2.28.0

[PATCH v10 15/17] drm/i915: panel: Honor the VBT PWM frequency for devs with an external PWM controller

[Hans de Goede]

So far for devices using an external PWM controller (devices using
pwm_setup_backlight()), we have been hardcoding the period-time passed to
pwm_config() to 21333 ns.

I suspect this was done because many VBTs set the PWM frequency to 200
which corresponds to a period-time of 5000000 ns, which greatly exceeds
the PWM_MAX_PERIOD_NS define in the Crystal Cove PMIC PWM driver, which
used to be 21333.

This PWM_MAX_PERIOD_NS define was actually based on a bug in the PWM
driver where its period and duty-cycle times where off by a factor of 256.

Due to this bug the hardcoded CRC_PMIC_PWM_PERIOD_NS value of 21333 would
result in the PWM driver using its divider of 128, which would result in
a PWM output frequency of 6000000 Hz / 256 / 128 = 183 Hz. So actually
pretty close to the default VBT value of 200 Hz.

Now that this bug in the pwm-crc driver is fixed, we can actually use
the VBT defined frequency.

This is important because:

a) With the pwm-crc driver fixed it will now translate the hardcoded
CRC_PMIC_PWM_PERIOD_NS value of 21333 ns / 46 Khz to a PWM output
frequency of 23 KHz (the max it can do).

b) The pwm-lpss driver used on many models has always honored the
21333 ns / 46 Khz request

Some panels do not like such high output frequencies. E.g. on a Terra
Pad 1061 tablet, using the LPSS PWM controller, the backlight would go
from off to max, when changing the sysfs backlight brightness value from
90-100%, anything under aprox. 90% would turn the backlight fully off.

Honoring the VBT specified PWM frequency will also hopefully fix the
various bug reports which we have received about users perceiving the
backlight to flicker after a suspend/resume cycle.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 .../drm/i915/display/intel_display_types.h    |  1 +
 drivers/gpu/drm/i915/display/intel_panel.c    | 19 +++++++++++--------
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index e8f809161c75..7171e7c8d928 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -223,6 +223,7 @@ struct intel_panel {
 		bool util_pin_active_low;	/* bxt+ */
 		u8 controller;		/* bxt+ only */
 		struct pwm_device *pwm;
+		int pwm_period_ns;
 
 		/* DPCD backlight */
 		u8 pwmgen_bit_count;
diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index df7472a3b9f8..5a13089d2fc0 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -40,8 +40,6 @@
 #include "intel_dsi_dcs_backlight.h"
 #include "intel_panel.h"
 
-#define CRC_PMIC_PWM_PERIOD_NS	21333
-
 void
 intel_fixed_panel_mode(const struct drm_display_mode *fixed_mode,
 		       struct drm_display_mode *adjusted_mode)
@@ -597,7 +595,7 @@ static u32 pwm_get_backlight(struct intel_connector *connector)
 	int duty_ns;
 
 	duty_ns = pwm_get_duty_cycle(panel->backlight.pwm);
-	return DIV_ROUND_UP(duty_ns * 100, CRC_PMIC_PWM_PERIOD_NS);
+	return DIV_ROUND_UP(duty_ns * 100, panel->backlight.pwm_period_ns);
 }
 
 static void lpt_set_backlight(const struct drm_connector_state *conn_state, u32 level)
@@ -671,9 +669,10 @@ static void bxt_set_backlight(const struct drm_connector_state *conn_state, u32
 static void pwm_set_backlight(const struct drm_connector_state *conn_state, u32 level)
 {
 	struct intel_panel *panel = &to_intel_connector(conn_state->connector)->panel;
-	int duty_ns = DIV_ROUND_UP(level * CRC_PMIC_PWM_PERIOD_NS, 100);
+	int duty_ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);
 
-	pwm_config(panel->backlight.pwm, duty_ns, CRC_PMIC_PWM_PERIOD_NS);
+	pwm_config(panel->backlight.pwm, duty_ns,
+		   panel->backlight.pwm_period_ns);
 }
 
 static void
@@ -1917,6 +1916,9 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 		return -ENODEV;
 	}
 
+	panel->backlight.pwm_period_ns = NSEC_PER_SEC /
+					 get_vbt_pwm_freq(dev_priv);
+
 	/*
 	 * FIXME: pwm_apply_args() should be removed when switching to
 	 * the atomic PWM API.
@@ -1926,9 +1928,10 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 	panel->backlight.min = 0; /* 0% */
 	panel->backlight.max = 100; /* 100% */
 	level = intel_panel_compute_brightness(connector, 100);
-	ns = DIV_ROUND_UP(level * CRC_PMIC_PWM_PERIOD_NS, 100);
+	ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);
 
-	retval = pwm_config(panel->backlight.pwm, ns, CRC_PMIC_PWM_PERIOD_NS);
+	retval = pwm_config(panel->backlight.pwm, ns,
+			    panel->backlight.pwm_period_ns);
 	if (retval < 0) {
 		drm_err(&dev_priv->drm, "Failed to configure the pwm chip\n");
 		pwm_put(panel->backlight.pwm);
@@ -1937,7 +1940,7 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 	}
 
 	level = DIV_ROUND_UP_ULL(pwm_get_duty_cycle(panel->backlight.pwm) * 100,
-			     CRC_PMIC_PWM_PERIOD_NS);
+				 panel->backlight.pwm_period_ns);
 	panel->backlight.level =
 		intel_panel_compute_brightness(connector, level);
 	panel->backlight.enabled = panel->backlight.level != 0;
-- 
2.28.0

[PATCH v10 16/17] drm/i915: panel: Honor the VBT PWM min setting for devs with an external PWM controller

[Hans de Goede]

So far for devices using an external PWM controller (devices using
pwm_setup_backlight()), we have been hardcoding the minimum allowed
PWM level to 0. But several of these devices specify a non 0 minimum
setting in their VBT.

Change pwm_setup_backlight() to use get_backlight_min_vbt() to get
the minimum level.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/gpu/drm/i915/display/intel_panel.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 5a13089d2fc0..2b27f9b07403 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -1925,8 +1925,8 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 	 */
 	pwm_apply_args(panel->backlight.pwm);
 
-	panel->backlight.min = 0; /* 0% */
 	panel->backlight.max = 100; /* 100% */
+	panel->backlight.min = get_backlight_min_vbt(connector);
 	level = intel_panel_compute_brightness(connector, 100);
 	ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);
 
@@ -1941,8 +1941,9 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 
 	level = DIV_ROUND_UP_ULL(pwm_get_duty_cycle(panel->backlight.pwm) * 100,
 				 panel->backlight.pwm_period_ns);
-	panel->backlight.level =
-		intel_panel_compute_brightness(connector, level);
+	level = intel_panel_compute_brightness(connector, level);
+	panel->backlight.level = clamp(level, panel->backlight.min,
+				       panel->backlight.max);
 	panel->backlight.enabled = panel->backlight.level != 0;
 
 	drm_info(&dev_priv->drm, "Using %s PWM for LCD backlight control\n",
-- 
2.28.0

[PATCH v10 17/17] drm/i915: panel: Use atomic PWM API for devs with an external PWM controller

[Hans de Goede]

Now that the PWM drivers which we use have been converted to the atomic
PWM API, we can move the i915 panel code over to using the atomic PWM API.

The removes a long standing FIXME and this removes a flicker where
the backlight brightness would jump to 100% when i915 loads even if
using the fastset path.

Note that this commit also simplifies pwm_disable_backlight(), by dropping
the intel_panel_actually_set_backlight(..., 0) call. This call sets the
PWM to 0% duty-cycle. I believe that this call was only present as a
workaround for a bug in the pwm-crc.c driver where it failed to clear the
PWM_OUTPUT_ENABLE bit. This is fixed by an earlier patch in this series.

After the dropping of this workaround, the usleep call, which seems
unnecessary to begin with, has no useful effect anymore, so drop that too.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v7:
- Fix a u64 divide leading to undefined reference to `__udivdi3' errors on 32 bit
  platforms by casting the divisor to an unsigned long

Changes in v6:
- Drop the pwm_get_period() check in pwm_setup(), it is now longer needed
  now that we use pwm_get_relative_duty_cycle()

Changes in v4:
- Add a note to the commit message about the dropping of the
  intel_panel_actually_set_backlight() and usleep() calls from
  pwm_disable_backlight()
- Use the pwm_set/get_relative_duty_cycle() helpers instead of using DIY code
  for this
---
 .../drm/i915/display/intel_display_types.h    |  3 +-
 drivers/gpu/drm/i915/display/intel_panel.c    | 70 ++++++++-----------
 2 files changed, 33 insertions(+), 40 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 7171e7c8d928..e3ebe7c313ba 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -28,6 +28,7 @@
 
 #include <linux/async.h>
 #include <linux/i2c.h>
+#include <linux/pwm.h>
 #include <linux/sched/clock.h>
 
 #include <drm/drm_atomic.h>
@@ -223,7 +224,7 @@ struct intel_panel {
 		bool util_pin_active_low;	/* bxt+ */
 		u8 controller;		/* bxt+ only */
 		struct pwm_device *pwm;
-		int pwm_period_ns;
+		struct pwm_state pwm_state;
 
 		/* DPCD backlight */
 		u8 pwmgen_bit_count;
diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 2b27f9b07403..2eb1a3a93df1 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -592,10 +592,10 @@ static u32 bxt_get_backlight(struct intel_connector *connector)
 static u32 pwm_get_backlight(struct intel_connector *connector)
 {
 	struct intel_panel *panel = &connector->panel;
-	int duty_ns;
+	struct pwm_state state;
 
-	duty_ns = pwm_get_duty_cycle(panel->backlight.pwm);
-	return DIV_ROUND_UP(duty_ns * 100, panel->backlight.pwm_period_ns);
+	pwm_get_state(panel->backlight.pwm, &state);
+	return pwm_get_relative_duty_cycle(&state, 100);
 }
 
 static void lpt_set_backlight(const struct drm_connector_state *conn_state, u32 level)
@@ -669,10 +669,9 @@ static void bxt_set_backlight(const struct drm_connector_state *conn_state, u32
 static void pwm_set_backlight(const struct drm_connector_state *conn_state, u32 level)
 {
 	struct intel_panel *panel = &to_intel_connector(conn_state->connector)->panel;
-	int duty_ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);
 
-	pwm_config(panel->backlight.pwm, duty_ns,
-		   panel->backlight.pwm_period_ns);
+	pwm_set_relative_duty_cycle(&panel->backlight.pwm_state, level, 100);
+	pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
 }
 
 static void
@@ -841,10 +840,8 @@ static void pwm_disable_backlight(const struct drm_connector_state *old_conn_sta
 	struct intel_connector *connector = to_intel_connector(old_conn_state->connector);
 	struct intel_panel *panel = &connector->panel;
 
-	/* Disable the backlight */
-	intel_panel_actually_set_backlight(old_conn_state, 0);
-	usleep_range(2000, 3000);
-	pwm_disable(panel->backlight.pwm);
+	panel->backlight.pwm_state.enabled = false;
+	pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
 }
 
 void intel_panel_disable_backlight(const struct drm_connector_state *old_conn_state)
@@ -1176,9 +1173,12 @@ static void pwm_enable_backlight(const struct intel_crtc_state *crtc_state,
 {
 	struct intel_connector *connector = to_intel_connector(conn_state->connector);
 	struct intel_panel *panel = &connector->panel;
+	int level = panel->backlight.level;
 
-	pwm_enable(panel->backlight.pwm);
-	intel_panel_actually_set_backlight(conn_state, panel->backlight.level);
+	level = intel_panel_compute_brightness(connector, level);
+	pwm_set_relative_duty_cycle(&panel->backlight.pwm_state, level, 100);
+	panel->backlight.pwm_state.enabled = true;
+	pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
 }
 
 static void __intel_panel_enable_backlight(const struct intel_crtc_state *crtc_state,
@@ -1897,8 +1897,7 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_panel *panel = &connector->panel;
 	const char *desc;
-	u32 level, ns;
-	int retval;
+	u32 level;
 
 	/* Get the right PWM chip for DSI backlight according to VBT */
 	if (dev_priv->vbt.dsi.config->pwm_blc == PPS_BLC_PMIC) {
@@ -1916,35 +1915,28 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 		return -ENODEV;
 	}
 
-	panel->backlight.pwm_period_ns = NSEC_PER_SEC /
-					 get_vbt_pwm_freq(dev_priv);
-
-	/*
-	 * FIXME: pwm_apply_args() should be removed when switching to
-	 * the atomic PWM API.
-	 */
-	pwm_apply_args(panel->backlight.pwm);
-
 	panel->backlight.max = 100; /* 100% */
 	panel->backlight.min = get_backlight_min_vbt(connector);
-	level = intel_panel_compute_brightness(connector, 100);
-	ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);
 
-	retval = pwm_config(panel->backlight.pwm, ns,
-			    panel->backlight.pwm_period_ns);
-	if (retval < 0) {
-		drm_err(&dev_priv->drm, "Failed to configure the pwm chip\n");
-		pwm_put(panel->backlight.pwm);
-		panel->backlight.pwm = NULL;
-		return retval;
-	}
+	if (pwm_is_enabled(panel->backlight.pwm)) {
+		/* PWM is already enabled, use existing settings */
+		pwm_get_state(panel->backlight.pwm, &panel->backlight.pwm_state);
 
-	level = DIV_ROUND_UP_ULL(pwm_get_duty_cycle(panel->backlight.pwm) * 100,
-				 panel->backlight.pwm_period_ns);
-	level = intel_panel_compute_brightness(connector, level);
-	panel->backlight.level = clamp(level, panel->backlight.min,
-				       panel->backlight.max);
-	panel->backlight.enabled = panel->backlight.level != 0;
+		level = pwm_get_relative_duty_cycle(&panel->backlight.pwm_state,
+						    100);
+		level = intel_panel_compute_brightness(connector, level);
+		panel->backlight.level = clamp(level, panel->backlight.min,
+					       panel->backlight.max);
+		panel->backlight.enabled = true;
+
+		drm_dbg_kms(&dev_priv->drm, "PWM already enabled at freq %ld, VBT freq %d, level %d\n",
+			    NSEC_PER_SEC / (unsigned long)panel->backlight.pwm_state.period,
+			    get_vbt_pwm_freq(dev_priv), level);
+	} else {
+		/* Set period from VBT frequency, leave other settings at 0. */
+		panel->backlight.pwm_state.period =
+			NSEC_PER_SEC / get_vbt_pwm_freq(dev_priv);
+	}
 
 	drm_info(&dev_priv->drm, "Using %s PWM for LCD backlight control\n",
 		 desc);
-- 
2.28.0