Date:   Fri, 10 Dec 2021 12:11:44 -0800
In-Reply-To: <20211210201144.1975655-1-rajatja@google.com>
Message-Id: <20211210201144.1975655-2-rajatja@google.com>
Mime-Version: 1.0
References: <20211210201144.1975655-1-rajatja@google.com>
Subject: [PATCH 2/2] platform/chrome: Add driver for ChromeOS privacy-screen
From:   Rajat Jain <rajatja@google.com>
To:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Hans de Goede <hdegoede@redhat.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Benson Leung <bleung@chromium.org>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        gwendal@google.com, seanpaul@google.com, marcheau@google.com,
        intel-gfx <intel-gfx@lists.freedesktop.org>
Cc:     Rajat Jain <rajatja@google.com>, rajatxjain@gmail.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

This adds the ACPI driver for the ChromeOS privacy screen that is
present on some chromeos devices.

Note that I found that ACPI drivers are bound to their devices AFTER
the drm probe. So on chromebooks with privacy-screen, this causes a
probe deferral for i915 driver, which results in a delay of about 250ms
in my experiments. However, per my personal experience, it did not
result in any user perceived delay of splash screen
(https://hansdegoede.livejournal.com/25948.html)

In future if this probe deferral turns out to be an issue, we can
consider turning this ACPI driver into something that is probed earlier
than the drm drivers.

Signed-off-by: Rajat Jain <rajatja@google.com>
---
This patch is rebased on top of linux-next/master

 drivers/platform/chrome/Kconfig              |  10 ++
 drivers/platform/chrome/Makefile             |   1 +
 drivers/platform/chrome/chromeos_priv_scrn.c | 133 +++++++++++++++++++
 3 files changed, 144 insertions(+)
 create mode 100644 drivers/platform/chrome/chromeos_priv_scrn.c

diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
index ccc23d8686e8..3f874bbd3d03 100644
--- a/drivers/platform/chrome/Kconfig
+++ b/drivers/platform/chrome/Kconfig
@@ -243,6 +243,16 @@ config CROS_USBPD_NOTIFY
 	  To compile this driver as a module, choose M here: the
 	  module will be called cros_usbpd_notify.
 
+config CHROMEOS_PRIVACY_SCREEN
+	bool "ChromeOS Privacy Screen support"
+	depends on ACPI
+	depends on DRM
+	default n
+	select DRM_PRIVACY_SCREEN
+	help
+	  This driver provides the support needed for the in-built electronic
+	  privacy screen that is present on some ChromeOS devices.
+
 source "drivers/platform/chrome/wilco_ec/Kconfig"
 
 endif # CHROMEOS_PLATFORMS
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index f901d2e43166..cfa0bb4e9e34 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -4,6 +4,7 @@
 CFLAGS_cros_ec_trace.o:=		-I$(src)
 
 obj-$(CONFIG_CHROMEOS_LAPTOP)		+= chromeos_laptop.o
+obj-$(CONFIG_CHROMEOS_PRIVACY_SCREEN)	+= chromeos_priv_scrn.o
 obj-$(CONFIG_CHROMEOS_PSTORE)		+= chromeos_pstore.o
 obj-$(CONFIG_CHROMEOS_TBMC)		+= chromeos_tbmc.o
 obj-$(CONFIG_CROS_EC)			+= cros_ec.o
diff --git a/drivers/platform/chrome/chromeos_priv_scrn.c b/drivers/platform/chrome/chromeos_priv_scrn.c
new file mode 100644
index 000000000000..00536154acd6
--- /dev/null
+++ b/drivers/platform/chrome/chromeos_priv_scrn.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ *  chromeos_priv_scrn.c - ChromeOS Privacy Screen support
+ *
+ * Copyright (C) 2022 The Chromium OS Authors
+ *
+ */
+
+#include <linux/acpi.h>
+#include <drm/drm_privacy_screen_driver.h>
+
+/*
+ * The DSM (Define Specific Method) constants below are the agreed API with
+ * the firmware team, on how to control privacy screen using ACPI methods.
+ */
+#define PRIV_SCRN_DSM_REVID		1	/* DSM version */
+#define PRIV_SCRN_DSM_FN_GET_STATUS	1	/* Get privacy screen status */
+#define PRIV_SCRN_DSM_FN_ENABLE		2	/* Enable privacy screen */
+#define PRIV_SCRN_DSM_FN_DISABLE	3	/* Disable privacy screen */
+
+static const guid_t chromeos_priv_scrn_dsm_guid =
+		    GUID_INIT(0xc7033113, 0x8720, 0x4ceb,
+			      0x90, 0x90, 0x9d, 0x52, 0xb3, 0xe5, 0x2d, 0x73);
+
+static void
+chromeos_priv_scrn_get_hw_state(struct drm_privacy_screen *drm_priv_scrn)
+{
+	union acpi_object *obj;
+	acpi_handle handle;
+	struct device *priv_scrn = drm_priv_scrn->dev.parent;
+
+	if (!priv_scrn)
+		return;
+
+	handle = acpi_device_handle(to_acpi_device(priv_scrn));
+	obj = acpi_evaluate_dsm(handle, &chromeos_priv_scrn_dsm_guid,
+				PRIV_SCRN_DSM_REVID,
+				PRIV_SCRN_DSM_FN_GET_STATUS, NULL);
+	if (!obj) {
+		dev_err(priv_scrn, "_DSM failed to get privacy-screen state\n");
+		return;
+	}
+
+	if (obj->type != ACPI_TYPE_INTEGER)
+		dev_err(priv_scrn, "Bad _DSM to get privacy-screen state\n");
+	else if (obj->integer.value == 1)
+		drm_priv_scrn->hw_state = drm_priv_scrn->sw_state =
+			PRIVACY_SCREEN_ENABLED;
+	else
+		drm_priv_scrn->hw_state = drm_priv_scrn->sw_state =
+			PRIVACY_SCREEN_DISABLED;
+
+	ACPI_FREE(obj);
+}
+
+static int
+chromeos_priv_scrn_set_sw_state(struct drm_privacy_screen *drm_priv_scrn,
+				enum drm_privacy_screen_status state)
+{
+	union acpi_object *obj = NULL;
+	acpi_handle handle;
+	struct device *priv_scrn = drm_priv_scrn->dev.parent;
+
+	if (!priv_scrn)
+		return -ENODEV;
+
+	handle = acpi_device_handle(to_acpi_device(priv_scrn));
+
+	if (state == PRIVACY_SCREEN_DISABLED) {
+		obj = acpi_evaluate_dsm(handle,	&chromeos_priv_scrn_dsm_guid,
+					PRIV_SCRN_DSM_REVID,
+					PRIV_SCRN_DSM_FN_DISABLE, NULL);
+	} else if (state == PRIVACY_SCREEN_ENABLED) {
+		obj = acpi_evaluate_dsm(handle,	&chromeos_priv_scrn_dsm_guid,
+					PRIV_SCRN_DSM_REVID,
+					PRIV_SCRN_DSM_FN_ENABLE, NULL);
+	} else {
+		dev_err(priv_scrn, "Bad attempt to set privacy-screen status\n");
+		return -EINVAL;
+	}
+
+	if (!obj) {
+		dev_err(priv_scrn, "_DSM failed to set privacy-screen state\n");
+		return -EIO;
+	}
+
+	drm_priv_scrn->hw_state = drm_priv_scrn->sw_state = state;
+	ACPI_FREE(obj);
+	return 0;
+}
+
+static const struct drm_privacy_screen_ops chromeos_priv_scrn_ops = {
+	.get_hw_state = chromeos_priv_scrn_get_hw_state,
+	.set_sw_state = chromeos_priv_scrn_set_sw_state,
+};
+
+static int chromeos_priv_scrn_add(struct acpi_device *adev)
+{
+	struct drm_privacy_screen *drm_priv_scrn =
+		drm_privacy_screen_register(&adev->dev, &chromeos_priv_scrn_ops);
+
+	if (IS_ERR(drm_priv_scrn)) {
+		dev_err(&adev->dev, "Error registering privacy-screen\n");
+		return PTR_ERR(drm_priv_scrn);
+	}
+
+	dev_info(&adev->dev, " registered privacy-screen '%s'\n",
+		 dev_name(&drm_priv_scrn->dev));
+
+	return 0;
+}
+
+static const struct acpi_device_id chromeos_priv_scrn_device_ids[] = {
+	{"GOOG0010", 0}, /* Google's electronic privacy screen for eDP-1 */
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, chromeos_priv_scrn_device_ids);
+
+static struct acpi_driver chromeos_priv_scrn_driver = {
+	.name = "chromeos_priv_scrn_drvr",
+	.class = "ChromeOS",
+	.ids = chromeos_priv_scrn_device_ids,
+	.ops = {
+		.add = chromeos_priv_scrn_add,
+	},
+	.owner = THIS_MODULE,
+};
+
+module_acpi_driver(chromeos_priv_scrn_driver);
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ChromeOS ACPI Privacy Screen driver");
+MODULE_AUTHOR("Rajat Jain <rajatja@google.com>");
-- 
2.34.1.173.g76aa8bc2d0-goog