Linux-ACPI Archive on lore.kernel.org
 help / color / Atom feed
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, Jani Nikula <jani.nikula@intel.com>
Subject: [PATCH v5 14/16] drm/i915: panel: Honor the VBT PWM frequency for devs with an external PWM controller
Date: Fri, 17 Jul 2020 15:37:51 +0200
Message-ID: <20200717133753.127282-15-hdegoede@redhat.com> (raw)
In-Reply-To: <20200717133753.127282-1-hdegoede@redhat.com>

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 2bf3d4cb4ea9..de32f9efb120 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 8efdd9f08a08..14e611c92194 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(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;
-- 
2.26.2


  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 ` [PATCH v5 06/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume Hans de Goede
2020-07-28 18:57   ` 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 ` Hans de Goede [this message]
2020-07-17 13:44 ` [PATCH v5 15/16] drm/i915: panel: Honor the VBT PWM min setting for devs with an external PWM controller 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200717133753.127282-15-hdegoede@redhat.com \
    --to=hdegoede@redhat.com \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=intel-gfx@lists.freedesktop.org \
    --cc=jani.nikula@intel.com \
    --cc=jani.nikula@linux.intel.com \
    --cc=joonas.lahtinen@linux.intel.com \
    --cc=lenb@kernel.org \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-pwm@vger.kernel.org \
    --cc=mika.westerberg@linux.intel.com \
    --cc=rjw@rjwysocki.net \
    --cc=rodrigo.vivi@intel.com \
    --cc=thierry.reding@gmail.com \
    --cc=u.kleine-koenig@pengutronix.de \
    --cc=ville.syrjala@linux.intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-ACPI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-acpi/0 linux-acpi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-acpi linux-acpi/ https://lore.kernel.org/linux-acpi \
		linux-acpi@vger.kernel.org
	public-inbox-index linux-acpi

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-acpi


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git