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From: Hans de Goede <hdegoede@redhat.com>
To: "Thierry Reding" <thierry.reding@gmail.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	"Len Brown" <lenb@kernel.org>
Cc: Hans de Goede <hdegoede@redhat.com>,
	linux-pwm@vger.kernel.org,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel@lists.freedesktop.org,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	linux-acpi@vger.kernel.org
Subject: [PATCH v5 06/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume
Date: Fri, 17 Jul 2020 15:37:43 +0200
Message-ID: <20200717133753.127282-7-hdegoede@redhat.com> (raw)
In-Reply-To: <20200717133753.127282-1-hdegoede@redhat.com>

Before this commit a suspend + resume of the LPSS PWM controller
would result in the controller being reset to its defaults of
output-freq = clock/256, duty-cycle=100%, until someone changes
to the output-freq and/or duty-cycle are made.

This problem has been masked so far because the main consumer
(the i915 driver) was always making duty-cycle changes on resume.
With the conversion of the i915 driver to the atomic PWM API the
driver now only disables/enables the PWM on suspend/resume leaving
the output-freq and duty as is, triggering this problem.

The LPSS PWM controller has a mechanism where the ctrl register value
and the actual base-unit and on-time-div values used are latched. When
software sets the SW_UPDATE bit then at the end of the current PWM cycle,
the new values from the ctrl-register will be latched into the actual
registers, and the SW_UPDATE bit will be cleared.

The problem is that before this commit our suspend/resume handling
consisted of simply saving the PWM ctrl register on suspend and
restoring it on resume, without setting the PWM_SW_UPDATE bit.
When the controller has lost its state over a suspend/resume and thus
has been reset to the defaults, just restoring the register is not
enough. We must also set the SW_UPDATE bit to tell the controller to
latch the restored values into the actual registers.

Fixing this problem is not as simple as just or-ing in the value which
is being restored with SW_UPDATE. If the PWM was enabled before we must
write the new settings + PWM_SW_UPDATE before setting PWM_ENABLE.
We must also wait for PWM_SW_UPDATE to become 0 again and depending on the
model we must do this either before or after the setting of PWM_ENABLE.

All the necessary logic for doing this is already present inside
pwm_lpss_apply(), so instead of duplicating this inside the resume
handler, this commit makes the resume handler use pwm_lpss_apply() to
restore the settings when necessary. This fixes the output-freq and
duty-cycle being reset to their defaults on resume.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v5:
- The changes to pwm_lpss_apply() are much cleaner now thanks to the new
  pwm_lpss_prepare_enable() helper.

Changes in v3:
- 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.
---
 drivers/pwm/pwm-lpss.c | 56 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 8a136ba2a583..cf4eaf7ef2a2 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -143,29 +143,39 @@ static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm,
 	return 0;
 }
 
-static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			  const struct pwm_state *state)
+static int __pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state, bool from_resume)
 {
 	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
 	int ret = 0;
 
 	if (state->enabled) {
 		if (!pwm_is_enabled(pwm)) {
-			pm_runtime_get_sync(chip->dev);
+			if (!from_resume)
+				pm_runtime_get_sync(chip->dev);
+
 			ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true);
-			if (ret)
+			if (ret && !from_resume)
 				pm_runtime_put(chip->dev);
 		} else {
 			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);
+
+		if (!from_resume)
+			pm_runtime_put(chip->dev);
 	}
 
 	return ret;
 }
 
+static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			  const struct pwm_state *state)
+{
+	return __pwm_lpss_apply(chip, pwm, state, false);
+}
+
 static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 			       struct pwm_state *state)
 {
@@ -278,10 +288,40 @@ EXPORT_SYMBOL_GPL(pwm_lpss_suspend);
 int pwm_lpss_resume(struct device *dev)
 {
 	struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
-	int i;
+	struct pwm_state saved_state;
+	struct pwm_device *pwm;
+	int i, ret;
+	u32 ctrl;
 
-	for (i = 0; i < lpwm->info->npwm; i++)
-		writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM);
+	for (i = 0; i < lpwm->info->npwm; i++) {
+		pwm = &lpwm->chip.pwms[i];
+
+		ctrl = pwm_lpss_read(pwm);
+		/* If we did not reach S0i3/S3 the controller keeps its state */
+		if (ctrl == lpwm->saved_ctrl[i])
+			continue;
+
+		/*
+		 * We cannot just blindly restore the old value here. Since we
+		 * are changing the settings we must set SW_UPDATE and if the
+		 * PWM was enabled before we must write the new settings +
+		 * PWM_SW_UPDATE before setting PWM_ENABLE. We must also wait
+		 * for PWM_SW_UPDATE to become 0 again and depending on the
+		 * model we must do this either before or after the setting of
+		 * PWM_ENABLE.
+		 * So instead of reproducing all the code from pwm_apply() here,
+		 * we just reapply the state as stored in pwm->state.
+		 */
+		saved_state = pwm->state;
+		/*
+		 * Update enabled to its actual setting for the
+		 * enabled<->disabled transitions inside apply().
+		 */
+		pwm->state.enabled = !!(ctrl & PWM_ENABLE);
+		ret = __pwm_lpss_apply(&lpwm->chip, pwm, &saved_state, true);
+		if (ret)
+			dev_err(dev, "Error restoring state on resume\n");
+	}
 
 	return 0;
 }
-- 
2.26.2


  parent reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-17 13:37 [PATCH v5 00/16] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API Hans de Goede
2020-07-17 13:37 ` [PATCH v5 01/16] ACPI / LPSS: Resume Cherry Trail PWM controller in no-irq phase Hans de Goede
2020-07-17 13:37 ` [PATCH v5 02/16] ACPI / LPSS: Save Cherry Trail PWM ctx registers only once (at activation) Hans de Goede
2020-07-17 13:37 ` [PATCH v5 03/16] pwm: lpss: Fix off by one error in base_unit math in pwm_lpss_prepare() Hans de Goede
2020-07-17 13:37 ` [PATCH v5 04/16] pwm: lpss: Add range limit check for the base_unit register value Hans de Goede
2020-07-17 13:37 ` [PATCH v5 05/16] pwm: lpss: Add pwm_lpss_prepare_enable() helper Hans de Goede
2020-07-28 18:45   ` Andy Shevchenko
2020-07-28 19:49     ` Hans de Goede
2020-07-17 13:37 ` Hans de Goede [this message]
2020-07-28 18:57   ` [PATCH v5 06/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume Andy Shevchenko
2020-07-28 19:55     ` Hans de Goede
2020-07-29  8:12       ` Andy Shevchenko
2020-08-02 20:51         ` Hans de Goede
2020-08-03  8:41           ` Andy Shevchenko
2020-07-17 13:37 ` [PATCH v5 07/16] pwm: crc: Fix period / duty_cycle times being off by a factor of 256 Hans de Goede
2020-07-28 19:36   ` Andy Shevchenko
2020-07-28 20:00     ` Hans de Goede
2020-07-29  8:13   ` Andy Shevchenko
2020-07-17 13:37 ` [PATCH v5 08/16] pwm: crc: Fix off-by-one error in the clock-divider calculations Hans de Goede
2020-07-29 10:28   ` Andy Shevchenko
2020-07-17 13:37 ` [PATCH v5 09/16] pwm: crc: Fix period changes not having any effect Hans de Goede
2020-07-29 10:30   ` Andy Shevchenko
2020-07-17 13:37 ` [PATCH v5 10/16] pwm: crc: Enable/disable PWM output on enable/disable Hans de Goede
2020-07-29 10:32   ` Andy Shevchenko
2020-07-17 13:37 ` [PATCH v5 11/16] pwm: crc: Implement apply() method to support the new atomic PWM API Hans de Goede
2020-07-29 10:51   ` Andy Shevchenko
2020-07-17 13:37 ` [PATCH v5 12/16] pwm: crc: Implement get_state() method Hans de Goede
2020-07-17 13:37 ` [PATCH v5 13/16] drm/i915: panel: Add get_vbt_pwm_freq() helper Hans de Goede
2020-07-17 13:37 ` [PATCH v5 14/16] drm/i915: panel: Honor the VBT PWM frequency for devs with an external PWM controller Hans de Goede
2020-07-17 13:44 ` [PATCH v5 15/16] drm/i915: panel: Honor the VBT PWM min setting " Hans de Goede
2020-07-17 13:44   ` [PATCH v5 16/16] drm/i915: panel: Use atomic PWM API " Hans de Goede
2020-07-27  7:41 ` [PATCH v5 00/16] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API Thierry Reding
2020-07-29  8:23   ` Andy Shevchenko
2020-07-29  9:32     ` Hans de Goede
2020-07-30  9:26       ` Thierry Reding
2020-08-01 14:33         ` Hans de Goede
2020-07-29 10:54 ` Andy Shevchenko
2020-08-01 14:38   ` Hans de Goede
2020-08-02 11:25     ` Andy Shevchenko
2020-08-02 19:43       ` Hans de Goede

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