From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Hans de Goede <hdegoede@redhat.com>
Cc: "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>,
linux-pwm@vger.kernel.org,
intel-gfx <intel-gfx@lists.freedesktop.org>,
dri-devel@lists.freedesktop.org,
"Mika Westerberg" <mika.westerberg@linux.intel.com>,
linux-acpi@vger.kernel.org
Subject: Re: [PATCH v4 05/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume
Date: Thu, 9 Jul 2020 16:36:09 +0300 [thread overview]
Message-ID: <20200709133609.GY3703480@smile.fi.intel.com> (raw)
In-Reply-To: <20200708211432.28612-6-hdegoede@redhat.com>
On Wed, Jul 08, 2020 at 11:14:21PM +0200, Hans de Goede wrote:
> 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.
...
> +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;
>
> 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_is_updating(pwm);
> if (ret) {
> - pm_runtime_put(chip->dev);
> + if (!from_resume)
> + 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) {
> - pm_runtime_put(chip->dev);
> + if (!from_resume)
> + pm_runtime_put(chip->dev);
> +
> return ret;
> }
> pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
> }
> } 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);
> }
I'm wondering if splitting more will make this look better, like:
...
if (from_resume) {
ret = pwm_lpss_prepare_enable(...); // whatever name you think suits better
} else {
pm_runtime_get_sync(...);
ret = pwm_lpss_prepare_enable(...);
if (ret)
pm_runtime_put(...);
}
...
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2020-07-09 13:36 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-08 21:14 [PATCH v4 00/15] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API Hans de Goede
2020-07-08 21:14 ` [PATCH v4 01/16] ACPI / LPSS: Resume Cherry Trail PWM controller in no-irq phase Hans de Goede
2020-07-08 21:14 ` [PATCH v4 02/16] ACPI / LPSS: Save Cherry Trail PWM ctx registers only once (at activation) Hans de Goede
2020-07-08 21:14 ` [PATCH v4 03/16] pwm: lpss: Fix off by one error in base_unit math in pwm_lpss_prepare() Hans de Goede
2020-07-08 21:14 ` [PATCH v4 04/16] pwm: lpss: Add range limit check for the base_unit register value Hans de Goede
2020-07-09 12:53 ` Andy Shevchenko
2020-07-09 13:23 ` Hans de Goede
2020-07-09 14:21 ` Andy Shevchenko
2020-07-09 14:33 ` Hans de Goede
2020-07-09 14:51 ` Andy Shevchenko
2020-07-08 21:14 ` [PATCH v4 05/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume Hans de Goede
2020-07-09 13:36 ` Andy Shevchenko [this message]
2020-07-09 13:48 ` Hans de Goede
2020-07-08 21:14 ` [PATCH v4 06/16] pwm: lpss: Correct get_state result for base_unit == 0 Hans de Goede
2020-07-09 14:50 ` Andy Shevchenko
2020-07-09 15:47 ` Hans de Goede
2020-07-11 6:11 ` Uwe Kleine-König
2020-07-11 13:58 ` Hans de Goede
2020-07-08 21:14 ` [PATCH v4 07/16] pwm: crc: Fix period / duty_cycle times being off by a factor of 256 Hans de Goede
2020-07-08 21:14 ` [PATCH v4 08/16] pwm: crc: Fix off-by-one error in the clock-divider calculations Hans de Goede
2020-07-08 21:14 ` [PATCH v4 09/16] pwm: crc: Fix period changes not having any effect Hans de Goede
2020-07-08 21:14 ` [PATCH v4 10/16] pwm: crc: Enable/disable PWM output on enable/disable Hans de Goede
2020-07-08 21:14 ` [PATCH v4 11/16] pwm: crc: Implement apply() method to support the new atomic PWM API Hans de Goede
2020-07-08 21:14 ` [PATCH v4 12/16] pwm: crc: Implement get_state() method Hans de Goede
2020-07-08 21:14 ` [PATCH v4 13/16] drm/i915: panel: Add get_vbt_pwm_freq() helper Hans de Goede
2020-07-08 21:14 ` [PATCH v4 14/16] drm/i915: panel: Honor the VBT PWM frequency for devs with an external PWM controller Hans de Goede
2020-07-08 21:14 ` [PATCH v4 15/16] drm/i915: panel: Honor the VBT PWM min setting " Hans de Goede
2020-07-08 21:14 ` [PATCH v4 16/16] drm/i915: panel: Use atomic PWM API " Hans de Goede
2020-07-11 6:32 ` Uwe Kleine-König
2020-07-11 13:51 ` Hans de Goede
2020-07-09 14:14 ` [PATCH v4 00/15] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API Sam Ravnborg
2020-07-09 14:40 ` Hans de Goede
2020-07-09 15:23 ` Sam Ravnborg
2020-07-11 6:19 ` Uwe Kleine-König
2020-07-11 13:46 ` Hans de Goede
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