[Buildroot] [PATCH 0/3] Buildroot support for Chromebook Elm

[Buildroot] [PATCH 0/3] Buildroot support for Chromebook Elm

[Bilal Wasim]

This patch series adds supports for generating Buildroot kernel + rootfs
images for the Arm Elm Chromebook
(https://www.acer.com/ac/en/US/content/series/acerchromebookr13).

A board is added under boards/chromebook which provides infrastructure
necessary to generate images. For example, the kernel.its file helps to
generate FIT image while the kernel.args file lists all the necessary
kernel command line params. Both of these files are used to generate a
signed kernel image by the sign.sh file. This folder also contains a
patch which must be applied to the linux kernel to get the HDMI working.
This patch is lying in "drm-misc-next" and should make it to the mainline
by 5.10, at which point it should be removed from buildroot and kernel
up-reved to 5.10 assuming nothing else fails. We also add a configuration
necessary to build the kernel.

In addition, a defconfig for Elm chromebook is added to make life easy for
the user. To generate kernel+rootfs, the user only needs to do
  make chromebook_elm_defconfig
  make menuconfig # If changes are required
  make -j ${nproc}

All of this is briefly mentioned in the readme file under the elm board file.

Bilal Wasim (3):
  configs: Add default configuration for Chromebook Elm.
  boards: chromebook: Move "mksd.sh" out of chromebook snow folder.
  boards: chromebook: Add support of Chromebook Elm

 board/chromebook/elm/kernel.args              |   1 +
 board/chromebook/elm/kernel.its               |  38 ++
 board/chromebook/elm/linux-5.9-elm-hdmi.patch | 404 ++++++++++++++++
 board/chromebook/elm/linux.config             | 453 ++++++++++++++++++
 board/chromebook/elm/readme.txt               |  56 +++
 board/chromebook/elm/sign.sh                  |  41 ++
 board/chromebook/{snow => }/mksd.sh           |   0
 configs/chromebook_elm_defconfig              |  35 ++
 configs/chromebook_snow_defconfig             |   2 +-
 9 files changed, 1029 insertions(+), 1 deletion(-)
 create mode 100644 board/chromebook/elm/kernel.args
 create mode 100644 board/chromebook/elm/kernel.its
 create mode 100644 board/chromebook/elm/linux-5.9-elm-hdmi.patch
 create mode 100644 board/chromebook/elm/linux.config
 create mode 100644 board/chromebook/elm/readme.txt
 create mode 100644 board/chromebook/elm/sign.sh
 rename board/chromebook/{snow => }/mksd.sh (100%)
 create mode 100644 configs/chromebook_elm_defconfig

-- 
2.25.1

[Buildroot] [PATCH 1/3] configs: Add default configuration for Chromebook Elm.

[Bilal Wasim]

The architecture of the MT8173 SoC is armv8-a in a big-little config.
This SoC is supported by the Chrome-OS linux kernel, but the mainline
support is reasonably good as well (benchmarks / conformance run fine)
and so that is used. For now, the kernel is 5.9-rc5 which will be uprevd
to 5.9 once its released.

The defconfig also lists all the tools (parted, vboot) that are necessary
to create a bootable image.

Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>
---
 configs/chromebook_elm_defconfig | 35 ++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 configs/chromebook_elm_defconfig

diff --git a/configs/chromebook_elm_defconfig b/configs/chromebook_elm_defconfig
new file mode 100644
index 0000000000..9b467ec6a8
--- /dev/null
+++ b/configs/chromebook_elm_defconfig
@@ -0,0 +1,35 @@
+# Architecture
+BR2_aarch64=y
+BR2_cortex_a72_a53=y
+
+# Filesystem
+BR2_TARGET_ROOTFS_EXT2=y
+BR2_TARGET_ROOTFS_EXT2_4=y
+
+# Kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.9-rc5"
+BR2_LINUX_KERNEL_PATCH="board/chromebook/elm/linux-5.9-elm-hdmi.patch"
+
+# Build Kernel with a Custom config.
+BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
+BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/chromebook/elm/linux.config"
+
+# DTS support
+BR2_LINUX_KERNEL_DTS_SUPPORT=y
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="mediatek/mt8173-elm"
+
+# Package Firmware for WiFi chip.
+BR2_PACKAGE_LINUX_FIRMWARE=y
+BR2_PACKAGE_LINUX_FIRMWARE_MWIFIEX_SD8797=y
+
+# Scripts to generate final images.
+BR2_ROOTFS_POST_BUILD_SCRIPT="board/chromebook/elm/sign.sh"
+BR2_ROOTFS_POST_IMAGE_SCRIPT="board/chromebook/mksd.sh"
+
+# Supporting host tools to build / sign FIT Image.
+BR2_PACKAGE_HOST_PARTED=y
+BR2_PACKAGE_HOST_UBOOT_TOOLS=y
+BR2_PACKAGE_HOST_UBOOT_TOOLS_FIT_SUPPORT=y
+BR2_PACKAGE_HOST_VBOOT_UTILS=y
-- 
2.25.1

[Buildroot] [PATCH 2/3] boards: chromebook: Move "mksd.sh" out of chromebook snow folder.

[Bilal Wasim]

The same script is used by Chromebook Elm to generate a bootable
SD / USB image. Therefore, move the script out of the snow folder
to one level above (boards/chromebook/snow -> boards/chromebook).

Update the Chrome snow defconfig to reflect the new location of the
script.

Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>
---
 board/chromebook/{snow => }/mksd.sh | 0
 configs/chromebook_snow_defconfig   | 2 +-
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename board/chromebook/{snow => }/mksd.sh (100%)

diff --git a/board/chromebook/snow/mksd.sh b/board/chromebook/mksd.sh
similarity index 100%
rename from board/chromebook/snow/mksd.sh
rename to board/chromebook/mksd.sh
diff --git a/configs/chromebook_snow_defconfig b/configs/chromebook_snow_defconfig
index 5558c101d6..bcb94b716b 100644
--- a/configs/chromebook_snow_defconfig
+++ b/configs/chromebook_snow_defconfig
@@ -4,7 +4,7 @@ BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_15=y
 BR2_TARGET_GENERIC_GETTY_PORT="tty1"
 BR2_TARGET_GENERIC_GETTY_TERM="linux"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/chromebook/snow/sign.sh"
-BR2_ROOTFS_POST_IMAGE_SCRIPT="board/chromebook/snow/mksd.sh"
+BR2_ROOTFS_POST_IMAGE_SCRIPT="board/chromebook/mksd.sh"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.15"
-- 
2.25.1

[Buildroot] [PATCH 3/3] boards: chromebook: Add support of Chromebook Elm

[Bilal Wasim]

This commit adds supports for building buildroot kernel + rootfs
for MT8173 Elm board, also known as Chromebook Elm
(https://www.acer.com/ac/en/US/content/series/acerchromebookr13).

Though Chrome-OS is officially supproted on this board, the
mainline kernel works as well (benchmarks + conformance), and so
the 5.9 kernel is used. As the 5.9 kernel isn't yet released, we
use the 5.9-rc5 for now, which will be up-revd to 5.9 once its
released.

Using the mainline kernel means that we have to apply certain
patches to get the HDMI screen working. These patches are lying
in the "drm-misc-next" list and will make it to the kernel after
5.9. At that time, we will remove the patches and point buildroot
to use the latest kernel (hopefully, 5.10).

This commit also adds an ITS file(for creating FIT images), an ARGS
file(for providing kernel args) and a "sign.sh" script to generate
signed kernel images.

Additionally a readme is added to help the user get started.

Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>
---
 board/chromebook/elm/kernel.args              |   1 +
 board/chromebook/elm/kernel.its               |  38 ++
 board/chromebook/elm/linux-5.9-elm-hdmi.patch | 404 ++++++++++++++++
 board/chromebook/elm/linux.config             | 453 ++++++++++++++++++
 board/chromebook/elm/readme.txt               |  56 +++
 board/chromebook/elm/sign.sh                  |  41 ++
 6 files changed, 993 insertions(+)
 create mode 100644 board/chromebook/elm/kernel.args
 create mode 100644 board/chromebook/elm/kernel.its
 create mode 100644 board/chromebook/elm/linux-5.9-elm-hdmi.patch
 create mode 100644 board/chromebook/elm/linux.config
 create mode 100644 board/chromebook/elm/readme.txt
 create mode 100644 board/chromebook/elm/sign.sh

diff --git a/board/chromebook/elm/kernel.args b/board/chromebook/elm/kernel.args
new file mode 100644
index 0000000000..848e179d68
--- /dev/null
+++ b/board/chromebook/elm/kernel.args
@@ -0,0 +1 @@
+root=PARTUUID=%U/PARTNROFF=1 rootwait rw noinitrd kern_guid=%U console=tty0
diff --git a/board/chromebook/elm/kernel.its b/board/chromebook/elm/kernel.its
new file mode 100644
index 0000000000..b92f8adb1f
--- /dev/null
+++ b/board/chromebook/elm/kernel.its
@@ -0,0 +1,38 @@
+/dts-v1/;
+  
+/ {
+	description = "Chrome OS kernel image with FDT";
+	#address-cells = <1>;
+
+	images {
+		kernel-1 {
+			data = /incbin/("Image");
+			type = "kernel_noload";
+			arch = "arm64";
+			os = "linux";
+			compression = "none";
+			load = <0>;
+			entry = <0>;
+		};
+
+		fdt-1 {
+			description = "mt8173-elm.dtb";
+			data = /incbin/("mt8173-elm.dtb");
+			type = "flat_dt";
+			arch = "arm64";
+			compression = "none";
+
+			hash-1 {
+				algo = "sha1";
+			};
+		};
+	};
+
+	configurations {
+		default = "conf-1";
+		conf-1 {
+			kernel = "kernel-1";
+			fdt = "fdt-1";
+		};
+	};
+};
diff --git a/board/chromebook/elm/linux-5.9-elm-hdmi.patch b/board/chromebook/elm/linux-5.9-elm-hdmi.patch
new file mode 100644
index 0000000000..7f549dcc6d
--- /dev/null
+++ b/board/chromebook/elm/linux-5.9-elm-hdmi.patch
@@ -0,0 +1,404 @@
+From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+To: linux-kernel at vger.kernel.org
+Cc: Collabora Kernel ML <kernel@collabora.com>, matthias.bgg at gmail.com,
+        drinkcat at chromium.org, hsinyi at chromium.org,
+        laurent.pinchart at ideasonboard.com, sam at ravnborg.org,
+        Daniel Vetter <daniel@ffwll.ch>,
+        David Airlie <airlied@linux.ie>,
+        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
+        Maxime Ripard <mripard@kernel.org>,
+        Thomas Zimmermann <tzimmermann@suse.de>,
+        dri-devel at lists.freedesktop.org
+Subject: [PATCH v2 1/5] drm/bridge_connector: Set default status connected for
+ eDP connectors
+Date: Wed, 26 Aug 2020 10:15:22 +0200
+
+In an eDP application, HPD is not required and on most bridge chips
+useless. If HPD is not used, we need to set initial status as connected,
+otherwise the connector created by the drm_bridge_connector API remains
+in an unknown state.
+
+Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+Acked-by: Sam Ravnborg <sam@ravnborg.org>
+Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+Reviewed-by: Bilal Wasim <bwasim.lkml@gmail.com>
+Tested-by: Bilal Wasim <bwasim.lkml@gmail.com>
+---
+
+Changes in v2:
+- Included the patch `drm/bridge_connector: Set default status connected for eDP connectors`
+
+ drivers/gpu/drm/drm_bridge_connector.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/drivers/gpu/drm/drm_bridge_connector.c b/drivers/gpu/drm/drm_bridge_connector.c
+index c6994fe673f3..a58cbde59c34 100644
+--- a/drivers/gpu/drm/drm_bridge_connector.c
++++ b/drivers/gpu/drm/drm_bridge_connector.c
+@@ -187,6 +187,7 @@ drm_bridge_connector_detect(struct drm_connector *connector, bool force)
+ 		case DRM_MODE_CONNECTOR_DPI:
+ 		case DRM_MODE_CONNECTOR_LVDS:
+ 		case DRM_MODE_CONNECTOR_DSI:
++		case DRM_MODE_CONNECTOR_eDP:
+ 			status = connector_status_connected;
+ 			break;
+ 		default:
+
+From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+To: linux-kernel at vger.kernel.org
+Cc: Collabora Kernel ML <kernel@collabora.com>, matthias.bgg at gmail.com,
+        drinkcat at chromium.org, hsinyi at chromium.org,
+        laurent.pinchart at ideasonboard.com, sam at ravnborg.org,
+        Andrzej Hajda <a.hajda@samsung.com>,
+        Daniel Vetter <daniel@ffwll.ch>,
+        David Airlie <airlied@linux.ie>,
+        Jernej Skrabec <jernej.skrabec@siol.net>,
+        Jonas Karlman <jonas@kwiboo.se>,
+        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
+        Neil Armstrong <narmstrong@baylibre.com>,
+        dri-devel at lists.freedesktop.org
+Subject: [PATCH v2 2/5] drm/bridge: ps8640: Get the EDID from eDP control
+Date: Wed, 26 Aug 2020 10:15:23 +0200
+
+The PS8640 DSI-to-eDP bridge can retrieve the EDID, so implement the
+.get_edid callback and set the flag to indicate the core to use it.
+
+Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+Acked-by: Sam Ravnborg <sam@ravnborg.org>
+Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+---
+
+Changes in v2:
+- Included the patch `drm/bridge: ps8640: Get the EDID from eDP control`
+
+ drivers/gpu/drm/bridge/parade-ps8640.c | 12 ++++++++++++
+ 1 file changed, 12 insertions(+)
+
+diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
+index 4b099196afeb..13755d278db6 100644
+--- a/drivers/gpu/drm/bridge/parade-ps8640.c
++++ b/drivers/gpu/drm/bridge/parade-ps8640.c
+@@ -242,8 +242,18 @@ static int ps8640_bridge_attach(struct drm_bridge *bridge,
+ 	return ret;
+ }
+ 
++static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
++					   struct drm_connector *connector)
++{
++	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
++
++	return drm_get_edid(connector,
++			    ps_bridge->page[PAGE0_DP_CNTL]->adapter);
++}
++
+ static const struct drm_bridge_funcs ps8640_bridge_funcs = {
+ 	.attach = ps8640_bridge_attach,
++	.get_edid = ps8640_bridge_get_edid,
+ 	.post_disable = ps8640_post_disable,
+ 	.pre_enable = ps8640_pre_enable,
+ };
+@@ -294,6 +304,8 @@ static int ps8640_probe(struct i2c_client *client)
+ 
+ 	ps_bridge->bridge.funcs = &ps8640_bridge_funcs;
+ 	ps_bridge->bridge.of_node = dev->of_node;
++	ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID;
++	ps_bridge->bridge.type = DRM_MODE_CONNECTOR_eDP;
+ 
+ 	ps_bridge->page[PAGE0_DP_CNTL] = client;
+ 
+From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+To: linux-kernel at vger.kernel.org
+Cc: Collabora Kernel ML <kernel@collabora.com>, matthias.bgg at gmail.com,
+        drinkcat at chromium.org, hsinyi at chromium.org,
+        laurent.pinchart at ideasonboard.com, sam at ravnborg.org,
+        Andrzej Hajda <a.hajda@samsung.com>,
+        Daniel Vetter <daniel@ffwll.ch>,
+        David Airlie <airlied@linux.ie>,
+        Jernej Skrabec <jernej.skrabec@siol.net>,
+        Jonas Karlman <jonas@kwiboo.se>,
+        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
+        Neil Armstrong <narmstrong@baylibre.com>,
+        dri-devel at lists.freedesktop.org
+Subject: [PATCH v2 3/5] drm/bridge: ps8640: Return an error for incorrect
+ attach flags
+Date: Wed, 26 Aug 2020 10:15:24 +0200
+
+Bridge drivers that implement the new model only shall return an error
+from their attach() handler when the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag
+is not set. So make sure we return an error because only the new
+drm_bridge model is supported.
+
+Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
+Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+Reviewed-by: Bilal Wasim <bwasim.lkml@gmail.com>
+Tested-by: Bilal Wasim <bwasim.lkml@gmail.com>
+---
+
+Changes in v2: None
+
+ drivers/gpu/drm/bridge/parade-ps8640.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
+index 13755d278db6..ce3e8b2da8c9 100644
+--- a/drivers/gpu/drm/bridge/parade-ps8640.c
++++ b/drivers/gpu/drm/bridge/parade-ps8640.c
+@@ -200,6 +200,10 @@ static int ps8640_bridge_attach(struct drm_bridge *bridge,
+ 						   .channel = 0,
+ 						   .node = NULL,
+ 						 };
++
++	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
++		return -EINVAL;
++
+ 	/* port at 0 is ps8640 dsi input port */
+ 	in_ep = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);
+ 	if (!in_ep)
+
+From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+To: linux-kernel at vger.kernel.org
+Cc: Collabora Kernel ML <kernel@collabora.com>, matthias.bgg at gmail.com,
+        drinkcat at chromium.org, hsinyi at chromium.org,
+        laurent.pinchart at ideasonboard.com, sam at ravnborg.org,
+        Andrzej Hajda <a.hajda@samsung.com>,
+        Daniel Vetter <daniel@ffwll.ch>,
+        David Airlie <airlied@linux.ie>,
+        Jernej Skrabec <jernej.skrabec@siol.net>,
+        Jonas Karlman <jonas@kwiboo.se>,
+        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
+        Neil Armstrong <narmstrong@baylibre.com>,
+        dri-devel at lists.freedesktop.org
+Subject: [PATCH v2 4/5] drm/bridge: ps8640: Print an error if VDO control
+ fails
+Date: Wed, 26 Aug 2020 10:15:25 +0200
+
+Print an error message inside ps8640_bridge_vdo_control() function when
+it fails so we can simplify a bit the callers, they will only need to
+check the error code.
+
+Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
+Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+Reviewed-by: Bilal Wasim <bwasim.lkml@gmail.com>
+Tested-by: Bilal Wasim <bwasim.lkml@gmail.com>
+---
+
+Changes in v2: None
+
+ drivers/gpu/drm/bridge/parade-ps8640.c | 13 ++++++-------
+ 1 file changed, 6 insertions(+), 7 deletions(-)
+
+diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
+index ce3e8b2da8c9..9f7b7a9c53c5 100644
+--- a/drivers/gpu/drm/bridge/parade-ps8640.c
++++ b/drivers/gpu/drm/bridge/parade-ps8640.c
+@@ -82,8 +82,11 @@ static int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
+ 	ret = i2c_smbus_write_i2c_block_data(client, PAGE3_SET_ADD,
+ 					     sizeof(vdo_ctrl_buf),
+ 					     vdo_ctrl_buf);
+-	if (ret < 0)
++	if (ret < 0) {
++		DRM_ERROR("failed to %sable VDO: %d\n",
++			  ctrl == ENABLE ? "en" : "dis", ret);
+ 		return ret;
++	}
+ 
+ 	return 0;
+ }
+@@ -150,10 +153,8 @@ static void ps8640_pre_enable(struct drm_bridge *bridge)
+ 	}
+ 
+ 	ret = ps8640_bridge_vdo_control(ps_bridge, ENABLE);
+-	if (ret) {
+-		DRM_ERROR("failed to enable VDO: %d\n", ret);
++	if (ret)
+ 		goto err_regulators_disable;
+-	}
+ 
+ 	/* Switch access edp panel's edid through i2c */
+ 	ret = i2c_smbus_write_byte_data(client, PAGE2_I2C_BYPASS,
+@@ -175,9 +176,7 @@ static void ps8640_post_disable(struct drm_bridge *bridge)
+ 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+ 	int ret;
+ 
+-	ret = ps8640_bridge_vdo_control(ps_bridge, DISABLE);
+-	if (ret < 0)
+-		DRM_ERROR("failed to disable VDO: %d\n", ret);
++	ps8640_bridge_vdo_control(ps_bridge, DISABLE);
+ 
+ 	gpiod_set_value(ps_bridge->gpio_reset, 1);
+ 	gpiod_set_value(ps_bridge->gpio_powerdown, 1);
+
+From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+To: linux-kernel at vger.kernel.org
+Cc: Collabora Kernel ML <kernel@collabora.com>, matthias.bgg at gmail.com,
+        drinkcat at chromium.org, hsinyi at chromium.org,
+        laurent.pinchart at ideasonboard.com, sam at ravnborg.org,
+        Andrzej Hajda <a.hajda@samsung.com>,
+        Daniel Vetter <daniel@ffwll.ch>,
+        David Airlie <airlied@linux.ie>,
+        Jernej Skrabec <jernej.skrabec@siol.net>,
+        Jonas Karlman <jonas@kwiboo.se>,
+        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
+        Neil Armstrong <narmstrong@baylibre.com>,
+        dri-devel at lists.freedesktop.org
+Subject: [PATCH v2 5/5] drm/bridge: ps8640: Rework power state handling
+Date: Wed, 26 Aug 2020 10:15:26 +0200
+
+The get_edid() callback can be triggered anytime by an ioctl, i.e
+
+  drm_mode_getconnector (ioctl)
+    -> drm_helper_probe_single_connector_modes
+       -> drm_bridge_connector_get_modes
+          -> ps8640_bridge_get_edid
+
+Actually if the bridge pre_enable() function was not called before
+get_edid(), the driver will not be able to get the EDID properly and
+display will not work until a second get_edid() call is issued and if
+pre_enable() is called before. The side effect of this, for example, is
+that you see anything when `Frecon` starts, neither the splash screen,
+until the graphical session manager starts.
+
+To fix this we need to make sure that all we need is enabled before
+reading the EDID. This means the following:
+
+1. If get_edid() is called before having the device powered we need to
+   power on the device. In such case, the driver will power off again the
+   device.
+
+2. If get_edid() is called after having the device powered, all should
+   just work. We added a powered flag in order to avoid recurrent calls
+   to ps8640_bridge_poweron() and unneeded delays.
+
+3. This seems to be specific for this device, but we need to make sure
+   the panel is powered on before do a power on cycle on this device.
+   Otherwise the device fails to retrieve the EDID.
+
+Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+---
+
+Changes in v2:
+- Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam Ravnborg)
+
+ drivers/gpu/drm/bridge/parade-ps8640.c | 64 +++++++++++++++++++++++---
+ 1 file changed, 58 insertions(+), 6 deletions(-)
+
+diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
+index 9f7b7a9c53c5..c5d76e209bda 100644
+--- a/drivers/gpu/drm/bridge/parade-ps8640.c
++++ b/drivers/gpu/drm/bridge/parade-ps8640.c
+@@ -65,6 +65,7 @@ struct ps8640 {
+ 	struct regulator_bulk_data supplies[2];
+ 	struct gpio_desc *gpio_reset;
+ 	struct gpio_desc *gpio_powerdown;
++	bool powered;
+ };
+ 
+ static inline struct ps8640 *bridge_to_ps8640(struct drm_bridge *e)
+@@ -91,13 +92,15 @@ static int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
+ 	return 0;
+ }
+ 
+-static void ps8640_pre_enable(struct drm_bridge *bridge)
++static void ps8640_bridge_poweron(struct ps8640 *ps_bridge)
+ {
+-	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+ 	struct i2c_client *client = ps_bridge->page[PAGE2_TOP_CNTL];
+ 	unsigned long timeout;
+ 	int ret, status;
+ 
++	if (ps_bridge->powered)
++		return;
++
+ 	ret = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
+ 				    ps_bridge->supplies);
+ 	if (ret < 0) {
+@@ -164,6 +167,8 @@ static void ps8640_pre_enable(struct drm_bridge *bridge)
+ 		goto err_regulators_disable;
+ 	}
+ 
++	ps_bridge->powered = true;
++
+ 	return;
+ 
+ err_regulators_disable:
+@@ -171,12 +176,12 @@ static void ps8640_pre_enable(struct drm_bridge *bridge)
+ 			       ps_bridge->supplies);
+ }
+ 
+-static void ps8640_post_disable(struct drm_bridge *bridge)
++static void ps8640_bridge_poweroff(struct ps8640 *ps_bridge)
+ {
+-	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+ 	int ret;
+ 
+-	ps8640_bridge_vdo_control(ps_bridge, DISABLE);
++	if (!ps_bridge->powered)
++		return;
+ 
+ 	gpiod_set_value(ps_bridge->gpio_reset, 1);
+ 	gpiod_set_value(ps_bridge->gpio_powerdown, 1);
+@@ -184,6 +189,28 @@ static void ps8640_post_disable(struct drm_bridge *bridge)
+ 				     ps_bridge->supplies);
+ 	if (ret < 0)
+ 		DRM_ERROR("cannot disable regulators %d\n", ret);
++
++	ps_bridge->powered = false;
++}
++
++static void ps8640_pre_enable(struct drm_bridge *bridge)
++{
++	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
++	int ret;
++
++	ps8640_bridge_poweron(ps_bridge);
++
++	ret = ps8640_bridge_vdo_control(ps_bridge, DISABLE);
++	if (ret < 0)
++		ps8640_bridge_poweroff(ps_bridge);
++}
++
++static void ps8640_post_disable(struct drm_bridge *bridge)
++{
++	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
++
++	ps8640_bridge_vdo_control(ps_bridge, DISABLE);
++	ps8640_bridge_poweroff(ps_bridge);
+ }
+ 
+ static int ps8640_bridge_attach(struct drm_bridge *bridge,
+@@ -249,9 +276,34 @@ static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
+ 					   struct drm_connector *connector)
+ {
+ 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
++	bool poweroff = !ps_bridge->powered;
++	struct edid *edid;
++
++	/*
++	 * When we end calling get_edid() triggered by an ioctl, i.e
++	 *
++	 *   drm_mode_getconnector (ioctl)
++	 *     -> drm_helper_probe_single_connector_modes
++	 *        -> drm_bridge_connector_get_modes
++	 *           -> ps8640_bridge_get_edid
++	 *
++	 * We need to make sure that what we need is enabled before reading
++	 * EDID, for this chip, we need to do a full poweron, otherwise it will
++	 * fail.
++	 */
++	drm_bridge_chain_pre_enable(bridge);
+ 
+-	return drm_get_edid(connector,
++	edid = drm_get_edid(connector,
+ 			    ps_bridge->page[PAGE0_DP_CNTL]->adapter);
++
++	/*
++	 * If we call the get_edid() function without having enabled the chip
++	 * before, return the chip to its original power state.
++	 */
++	if (poweroff)
++		drm_bridge_chain_post_disable(bridge);
++
++	return edid;
+ }
+ 
+ static const struct drm_bridge_funcs ps8640_bridge_funcs = {
diff --git a/board/chromebook/elm/linux.config b/board/chromebook/elm/linux.config
new file mode 100644
index 0000000000..50402eae8a
--- /dev/null
+++ b/board/chromebook/elm/linux.config
@@ -0,0 +1,453 @@
+CONFIG_SYSVIPC=y
+CONFIG_NO_HZ_IDLE=y
+CONFIG_HIGH_RES_TIMERS=y
+CONFIG_PREEMPT=y
+CONFIG_IRQ_TIME_ACCOUNTING=y
+CONFIG_BSD_PROCESS_ACCT=y
+CONFIG_BSD_PROCESS_ACCT_V3=y
+CONFIG_IKCONFIG=y
+CONFIG_IKCONFIG_PROC=y
+CONFIG_NUMA_BALANCING=y
+CONFIG_MEMCG=y
+CONFIG_BLK_CGROUP=y
+CONFIG_CGROUP_PIDS=y
+CONFIG_CGROUP_HUGETLB=y
+CONFIG_CPUSETS=y
+CONFIG_CGROUP_DEVICE=y
+CONFIG_CGROUP_CPUACCT=y
+CONFIG_CGROUP_PERF=y
+CONFIG_USER_NS=y
+CONFIG_SCHED_AUTOGROUP=y
+CONFIG_RELAY=y
+CONFIG_BLK_DEV_INITRD=y
+CONFIG_KALLSYMS_ALL=y
+# CONFIG_COMPAT_BRK is not set
+CONFIG_SLAB=y
+CONFIG_PROFILING=y
+CONFIG_ARCH_MEDIATEK=y
+CONFIG_ARM64_VA_BITS_48=y
+CONFIG_SCHED_MC=y
+CONFIG_SCHED_SMT=y
+CONFIG_NR_CPUS=4
+CONFIG_NUMA=y
+CONFIG_SECCOMP=y
+CONFIG_PARAVIRT=y
+CONFIG_CRASH_DUMP=y
+CONFIG_COMPAT=y
+CONFIG_RANDOMIZE_BASE=y
+# CONFIG_EFI is not set
+# CONFIG_SUSPEND is not set
+CONFIG_PM=y
+CONFIG_PM_DEBUG=y
+CONFIG_PM_ADVANCED_DEBUG=y
+CONFIG_CPU_IDLE=y
+CONFIG_CPU_IDLE_GOV_LADDER=y
+CONFIG_ARM_CPUIDLE=y
+CONFIG_ARM_PSCI_CPUIDLE=y
+CONFIG_CPU_FREQ=y
+CONFIG_CPU_FREQ_STAT=y
+CONFIG_CPU_FREQ_GOV_POWERSAVE=y
+CONFIG_CPU_FREQ_GOV_USERSPACE=y
+CONFIG_CPU_FREQ_GOV_ONDEMAND=y
+CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
+CONFIG_CPU_FREQ_GOV_SCHEDUTIL=y
+CONFIG_CPUFREQ_DT=y
+CONFIG_ARM_SCPI_CPUFREQ=y
+CONFIG_ARM_MEDIATEK_CPUFREQ=y
+CONFIG_ARM_SCPI_PROTOCOL=y
+CONFIG_JUMP_LABEL=y
+CONFIG_MODULES=y
+CONFIG_MODULE_UNLOAD=y
+# CONFIG_BLK_DEBUG_FS is not set
+# CONFIG_MQ_IOSCHED_KYBER is not set
+# CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is not set
+CONFIG_KSM=y
+CONFIG_MEMORY_FAILURE=y
+CONFIG_TRANSPARENT_HUGEPAGE=y
+CONFIG_CMA=y
+CONFIG_NET=y
+CONFIG_PACKET=y
+CONFIG_UNIX=y
+CONFIG_UNIX_DIAG=y
+CONFIG_INET=y
+CONFIG_IP_MULTICAST=y
+CONFIG_INET_UDP_DIAG=y
+# CONFIG_IPV6 is not set
+CONFIG_CFG80211=y
+# CONFIG_CFG80211_DEFAULT_PS is not set
+CONFIG_MAC80211=y
+CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
+CONFIG_FW_LOADER_USER_HELPER=y
+CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
+CONFIG_BRCMSTB_GISB_ARB=y
+CONFIG_VEXPRESS_CONFIG=y
+CONFIG_MTD=y
+CONFIG_MTD_BLOCK=y
+CONFIG_MTD_CFI=y
+CONFIG_MTD_CFI_ADV_OPTIONS=y
+CONFIG_MTD_CFI_INTELEXT=y
+CONFIG_MTD_CFI_AMDSTD=y
+CONFIG_MTD_CFI_STAA=y
+CONFIG_MTD_PHYSMAP=y
+CONFIG_MTD_PHYSMAP_OF=y
+CONFIG_MTD_DATAFLASH=y
+CONFIG_MTD_SST25L=y
+CONFIG_MTD_RAW_NAND=y
+CONFIG_MTD_NAND_DENALI_DT=y
+CONFIG_MTD_SPI_NOR=y
+CONFIG_SPI_CADENCE_QUADSPI=y
+CONFIG_OF_OVERLAY=y
+# CONFIG_BLK_DEV is not set
+CONFIG_SRAM=y
+CONFIG_EEPROM_AT24=m
+CONFIG_EEPROM_AT25=m
+CONFIG_RAID_ATTRS=m
+CONFIG_SCSI=y
+# CONFIG_SCSI_PROC_FS is not set
+CONFIG_BLK_DEV_SD=y
+CONFIG_SCSI_SAS_LIBSAS=y
+CONFIG_SCSI_UFSHCD=y
+CONFIG_SCSI_UFSHCD_PLATFORM=y
+CONFIG_MD=y
+CONFIG_BLK_DEV_MD=m
+CONFIG_BLK_DEV_DM=m
+CONFIG_DM_MIRROR=m
+CONFIG_DM_ZERO=m
+CONFIG_NETDEVICES=y
+# CONFIG_ETHERNET is not set
+CONFIG_USB_RTL8152=y
+CONFIG_USB_USBNET=y
+# CONFIG_USB_NET_AX88179_178A is not set
+# CONFIG_USB_NET_NET1080 is not set
+# CONFIG_USB_NET_CDC_SUBSET is not set
+# CONFIG_USB_NET_ZAURUS is not set
+# CONFIG_WLAN_VENDOR_ADMTEK is not set
+# CONFIG_WLAN_VENDOR_ATH is not set
+# CONFIG_WLAN_VENDOR_ATMEL is not set
+# CONFIG_WLAN_VENDOR_BROADCOM is not set
+# CONFIG_WLAN_VENDOR_CISCO is not set
+# CONFIG_WLAN_VENDOR_INTEL is not set
+# CONFIG_WLAN_VENDOR_INTERSIL is not set
+CONFIG_MWIFIEX=m
+CONFIG_MWIFIEX_SDIO=m
+# CONFIG_WLAN_VENDOR_MEDIATEK is not set
+# CONFIG_WLAN_VENDOR_RALINK is not set
+# CONFIG_WLAN_VENDOR_REALTEK is not set
+# CONFIG_WLAN_VENDOR_RSI is not set
+# CONFIG_WLAN_VENDOR_ST is not set
+# CONFIG_WLAN_VENDOR_TI is not set
+# CONFIG_WLAN_VENDOR_ZYDAS is not set
+# CONFIG_WLAN_VENDOR_QUANTENNA is not set
+CONFIG_INPUT_POLLDEV=m
+CONFIG_INPUT_EVDEV=y
+CONFIG_KEYBOARD_ADC=m
+CONFIG_KEYBOARD_GPIO=y
+CONFIG_KEYBOARD_CROS_EC=y
+CONFIG_MOUSE_ELAN_I2C=y
+CONFIG_INPUT_TOUCHSCREEN=y
+CONFIG_TOUCHSCREEN_ATMEL_MXT=m
+CONFIG_TOUCHSCREEN_ELAN=y
+CONFIG_INPUT_MISC=y
+# CONFIG_SERIO_SERPORT is not set
+CONFIG_SERIO_AMBAKMI=y
+CONFIG_LEGACY_PTY_COUNT=16
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_8250_EXTENDED=y
+CONFIG_SERIAL_8250_SHARE_IRQ=y
+CONFIG_SERIAL_8250_DW=y
+CONFIG_SERIAL_8250_MT6577=y
+CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_SERIAL_AMBA_PL011=y
+CONFIG_SERIAL_AMBA_PL011_CONSOLE=y
+CONFIG_SERIAL_XILINX_PS_UART=y
+CONFIG_SERIAL_XILINX_PS_UART_CONSOLE=y
+CONFIG_SERIAL_FSL_LPUART=y
+CONFIG_SERIAL_FSL_LPUART_CONSOLE=y
+CONFIG_SERIAL_FSL_LINFLEXUART=y
+CONFIG_SERIAL_FSL_LINFLEXUART_CONSOLE=y
+CONFIG_SERIAL_DEV_BUS=y
+CONFIG_VIRTIO_CONSOLE=y
+CONFIG_IPMI_HANDLER=m
+CONFIG_IPMI_DEVICE_INTERFACE=m
+CONFIG_IPMI_SI=m
+CONFIG_TCG_TPM=y
+CONFIG_TCG_TIS_I2C_INFINEON=y
+CONFIG_I2C_CHARDEV=y
+CONFIG_I2C_MUX_PCA954x=y
+CONFIG_I2C_DESIGNWARE_PLATFORM=y
+CONFIG_I2C_GPIO=m
+CONFIG_I2C_MT65XX=y
+CONFIG_I2C_RK3X=y
+CONFIG_I2C_CROS_EC_TUNNEL=y
+CONFIG_I2C_SLAVE=y
+CONFIG_SPI=y
+CONFIG_SPI_NXP_FLEXSPI=y
+CONFIG_SPI_GPIO=y
+CONFIG_SPI_MT65XX=y
+CONFIG_SPI_PL022=y
+CONFIG_SPI_ROCKCHIP=y
+CONFIG_SPI_SPIDEV=y
+CONFIG_PINCTRL_SINGLE=y
+CONFIG_PINCTRL_MAX77620=y
+CONFIG_GPIO_ALTERA=m
+CONFIG_GPIO_DWAPB=y
+CONFIG_GPIO_MB86S7X=y
+CONFIG_GPIO_PL061=y
+CONFIG_GPIO_XGENE=y
+CONFIG_GPIO_MAX732X=y
+CONFIG_GPIO_PCA953X=y
+CONFIG_GPIO_PCA953X_IRQ=y
+CONFIG_GPIO_BD9571MWV=m
+CONFIG_GPIO_MAX77620=y
+CONFIG_POWER_AVS=y
+CONFIG_POWER_RESET_BRCMSTB=y
+CONFIG_POWER_RESET_XGENE=y
+CONFIG_POWER_RESET_SYSCON=y
+CONFIG_SYSCON_REBOOT_MODE=y
+CONFIG_BATTERY_SBS=m
+CONFIG_BATTERY_BQ27XXX=y
+CONFIG_SENSORS_ARM_SCPI=y
+CONFIG_SENSORS_LM90=m
+CONFIG_SENSORS_PWM_FAN=m
+CONFIG_SENSORS_INA2XX=m
+CONFIG_SENSORS_INA3221=m
+CONFIG_THERMAL=y
+CONFIG_CPU_THERMAL=y
+CONFIG_DEVFREQ_THERMAL=y
+CONFIG_THERMAL_EMULATION=y
+CONFIG_WATCHDOG=y
+CONFIG_MEDIATEK_WATCHDOG=y
+CONFIG_MFD_BD9571MWV=y
+CONFIG_MFD_AXP20X_I2C=y
+CONFIG_MFD_HI6421_PMIC=y
+CONFIG_MFD_MAX77620=y
+CONFIG_MFD_MT6397=y
+CONFIG_MFD_RK808=y
+CONFIG_MFD_SEC_CORE=y
+CONFIG_MFD_ROHM_BD718XX=y
+CONFIG_REGULATOR_DEBUG=y
+CONFIG_REGULATOR_FIXED_VOLTAGE=y
+CONFIG_REGULATOR_AXP20X=y
+CONFIG_REGULATOR_BD718XX=y
+CONFIG_REGULATOR_BD9571MWV=y
+CONFIG_REGULATOR_DA9211=y
+CONFIG_REGULATOR_FAN53555=y
+CONFIG_REGULATOR_GPIO=y
+CONFIG_REGULATOR_HI6421V530=y
+CONFIG_REGULATOR_MAX77620=y
+CONFIG_REGULATOR_MAX8973=y
+CONFIG_REGULATOR_MT6397=y
+CONFIG_REGULATOR_PFUZE100=y
+CONFIG_REGULATOR_PWM=y
+CONFIG_REGULATOR_RK808=y
+CONFIG_REGULATOR_S2MPS11=y
+CONFIG_REGULATOR_VCTRL=m
+CONFIG_MEDIA_SUPPORT=y
+CONFIG_MEDIA_CAMERA_SUPPORT=y
+CONFIG_MEDIA_ANALOG_TV_SUPPORT=y
+CONFIG_MEDIA_DIGITAL_TV_SUPPORT=y
+CONFIG_MEDIA_SDR_SUPPORT=y
+CONFIG_VIDEO_V4L2_SUBDEV_API=y
+CONFIG_MEDIA_USB_SUPPORT=y
+CONFIG_USB_VIDEO_CLASS=m
+CONFIG_DRM=y
+CONFIG_DRM_I2C_CH7006=m
+CONFIG_DRM_I2C_SIL164=m
+CONFIG_DRM_I2C_NXP_TDA998X=m
+CONFIG_DRM_MALI_DISPLAY=m
+CONFIG_DRM_PANEL_LVDS=m
+CONFIG_DRM_PANEL_SIMPLE=y
+CONFIG_DRM_PANEL_TRULY_NT35597_WQXGA=m
+CONFIG_DRM_DISPLAY_CONNECTOR=y
+CONFIG_DRM_PARADE_PS8640=y
+CONFIG_DRM_SII902X=m
+CONFIG_DRM_THINE_THC63LVD1024=m
+CONFIG_DRM_TI_SN65DSI86=m
+CONFIG_DRM_ANALOGIX_ANX78XX=y
+CONFIG_DRM_I2C_ADV7511=m
+CONFIG_DRM_MEDIATEK=y
+CONFIG_DRM_MEDIATEK_HDMI=y
+CONFIG_FB_MODE_HELPERS=y
+CONFIG_FB_SIMPLE=y
+CONFIG_BACKLIGHT_CLASS_DEVICE=y
+CONFIG_BACKLIGHT_PWM=y
+CONFIG_BACKLIGHT_LP855X=y
+CONFIG_SOUND=y
+CONFIG_SND=y
+CONFIG_SND_SOC=y
+CONFIG_SND_SOC_MT8173=y
+CONFIG_SND_SOC_MT8173_RT5650_RT5676=y
+CONFIG_I2C_HID=m
+CONFIG_USB_CONN_GPIO=y
+CONFIG_USB=y
+CONFIG_USB_XHCI_HCD=y
+CONFIG_USB_EHCI_HCD=y
+CONFIG_USB_EHCI_HCD_PLATFORM=y
+CONFIG_USB_OHCI_HCD=y
+CONFIG_USB_OHCI_HCD_PLATFORM=y
+CONFIG_USB_STORAGE=y
+CONFIG_USB_MTU3=y
+CONFIG_USB_MUSB_HDRC=y
+CONFIG_USB_DWC3=y
+CONFIG_USB_DWC2=y
+CONFIG_USB_CHIPIDEA=y
+CONFIG_USB_CHIPIDEA_UDC=y
+CONFIG_USB_CHIPIDEA_HOST=y
+CONFIG_USB_ISP1760=y
+CONFIG_USB_SERIAL=y
+CONFIG_USB_SERIAL_CONSOLE=y
+CONFIG_USB_SERIAL_PL2303=y
+CONFIG_USB_HSIC_USB3503=y
+CONFIG_NOP_USB_XCEIV=y
+CONFIG_USB_ULPI=y
+CONFIG_USB_GADGET=y
+CONFIG_USB_SNP_UDC_PLAT=y
+CONFIG_USB_BDC_UDC=y
+CONFIG_USB_ETH=m
+CONFIG_USB_ETH_EEM=y
+CONFIG_TYPEC=m
+CONFIG_TYPEC_TCPM=m
+CONFIG_TYPEC_FUSB302=m
+CONFIG_MMC=y
+CONFIG_MMC_BLOCK_MINORS=32
+CONFIG_MMC_ARMMMCI=y
+CONFIG_MMC_SDHCI=y
+CONFIG_MMC_SDHCI_PLTFM=y
+CONFIG_MMC_SDHCI_OF_ARASAN=y
+CONFIG_MMC_SDHCI_CADENCE=y
+CONFIG_MMC_SDHCI_F_SDH30=y
+CONFIG_MMC_SPI=y
+CONFIG_MMC_DW=y
+CONFIG_MMC_DW_EXYNOS=y
+CONFIG_MMC_DW_HI3798CV200=y
+CONFIG_MMC_DW_K3=y
+CONFIG_MMC_MTK=y
+CONFIG_MMC_SDHCI_XENON=y
+CONFIG_NEW_LEDS=y
+CONFIG_LEDS_CLASS=y
+CONFIG_LEDS_GPIO=y
+CONFIG_LEDS_PWM=y
+CONFIG_LEDS_SYSCON=y
+CONFIG_LEDS_TRIGGERS=y
+CONFIG_LEDS_TRIGGER_TIMER=y
+CONFIG_LEDS_TRIGGER_HEARTBEAT=y
+CONFIG_LEDS_TRIGGER_CPU=y
+CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
+CONFIG_LEDS_TRIGGER_PANIC=y
+CONFIG_RTC_CLASS=y
+CONFIG_RTC_DRV_DS1307=m
+CONFIG_RTC_DRV_MAX77686=y
+CONFIG_RTC_DRV_RK808=m
+CONFIG_RTC_DRV_PCF85363=m
+CONFIG_RTC_DRV_RX8581=m
+CONFIG_RTC_DRV_S5M=y
+CONFIG_RTC_DRV_DS3232=y
+CONFIG_RTC_DRV_PCF2127=m
+CONFIG_RTC_DRV_CROS_EC=y
+CONFIG_RTC_DRV_PL031=y
+CONFIG_DMADEVICES=y
+CONFIG_FSL_EDMA=y
+CONFIG_MV_XOR_V2=y
+CONFIG_PL330_DMA=y
+CONFIG_MTK_CQDMA=y
+CONFIG_QCOM_HIDMA_MGMT=y
+CONFIG_QCOM_HIDMA=y
+# CONFIG_VIRTIO_MENU is not set
+CONFIG_MFD_CROS_EC=y
+CONFIG_CROS_EC_I2C=y
+CONFIG_CROS_EC_SPI=y
+CONFIG_COMMON_CLK_RK808=y
+CONFIG_COMMON_CLK_SCPI=y
+CONFIG_COMMON_CLK_CS2000_CP=y
+CONFIG_COMMON_CLK_S2MPS11=y
+CONFIG_CLK_QORIQ=y
+CONFIG_COMMON_CLK_XGENE=y
+CONFIG_COMMON_CLK_PWM=y
+CONFIG_COMMON_CLK_VC5=y
+CONFIG_COMMON_CLK_MT6797_MMSYS=y
+CONFIG_COMMON_CLK_MT6797_IMGSYS=y
+CONFIG_COMMON_CLK_MT6797_VDECSYS=y
+CONFIG_COMMON_CLK_MT6797_VENCSYS=y
+CONFIG_HWSPINLOCK=y
+CONFIG_ARM_MHU=y
+CONFIG_PLATFORM_MHU=y
+CONFIG_ARM_SMMU=y
+CONFIG_ARM_SMMU_V3=y
+CONFIG_MTK_IOMMU=y
+CONFIG_REMOTEPROC=y
+CONFIG_MTK_CMDQ=y
+CONFIG_MTK_PMIC_WRAP=y
+CONFIG_EXTCON_USB_GPIO=y
+CONFIG_EXTCON_USBC_CROS_EC=y
+CONFIG_IIO=y
+CONFIG_MAX9611=m
+CONFIG_IIO_CROS_EC_SENSORS_CORE=m
+CONFIG_IIO_CROS_EC_SENSORS=m
+CONFIG_IIO_CROS_EC_LIGHT_PROX=m
+CONFIG_SENSORS_ISL29018=m
+CONFIG_IIO_CROS_EC_BARO=m
+CONFIG_MPL3115=m
+CONFIG_PWM=y
+CONFIG_PWM_CROS_EC=m
+CONFIG_PWM_MTK_DISP=y
+CONFIG_PWM_MEDIATEK=y
+CONFIG_PHY_XGENE=y
+CONFIG_PHY_FSL_IMX8MQ_USB=y
+CONFIG_PHY_MTK_TPHY=y
+CONFIG_PHY_QCOM_USB_HS=y
+CONFIG_PHY_SAMSUNG_USB2=y
+CONFIG_EXT2_FS=y
+CONFIG_EXT3_FS=y
+CONFIG_EXT4_FS_POSIX_ACL=y
+CONFIG_FANOTIFY=y
+CONFIG_FANOTIFY_ACCESS_PERMISSIONS=y
+CONFIG_QUOTA=y
+CONFIG_AUTOFS4_FS=y
+CONFIG_FUSE_FS=m
+CONFIG_CUSE=m
+CONFIG_OVERLAY_FS=y
+CONFIG_OVERLAY_FS_INDEX=y
+CONFIG_OVERLAY_FS_XINO_AUTO=y
+CONFIG_OVERLAY_FS_METACOPY=y
+CONFIG_VFAT_FS=y
+CONFIG_TMPFS=y
+CONFIG_TMPFS_POSIX_ACL=y
+CONFIG_HUGETLBFS=y
+CONFIG_CONFIGFS_FS=y
+CONFIG_PSTORE=y
+CONFIG_NLS_CODEPAGE_437=y
+CONFIG_NLS_ISO8859_1=y
+CONFIG_SECURITY=y
+CONFIG_CRYPTO_CRYPTD=y
+CONFIG_CRYPTO_DH=m
+CONFIG_CRYPTO_ECDH=m
+CONFIG_CRYPTO_SEQIV=y
+CONFIG_CRYPTO_ECHAINIV=y
+CONFIG_CRYPTO_CBC=y
+CONFIG_CRYPTO_ECB=y
+CONFIG_CRYPTO_XXHASH=m
+CONFIG_CRYPTO_SHA1=y
+CONFIG_CRYPTO_SHA3=m
+CONFIG_CRYPTO_DES=m
+CONFIG_CRYPTO_ANSI_CPRNG=y
+CONFIG_CRYPTO_DEV_CCREE=m
+CONFIG_PACKING=y
+CONFIG_INDIRECT_PIO=y
+CONFIG_CRC_CCITT=m
+CONFIG_CRC_T10DIF=y
+CONFIG_LIBCRC32C=m
+CONFIG_DMA_CMA=y
+CONFIG_CMA_SIZE_MBYTES=32
+CONFIG_IRQ_POLL=y
+CONFIG_PRINTK_TIME=y
+CONFIG_DEBUG_INFO=y
+CONFIG_MAGIC_SYSRQ=y
+CONFIG_DEBUG_FS=y
+CONFIG_DEBUG_KERNEL=y
+# CONFIG_SCHED_DEBUG is not set
+# CONFIG_DEBUG_PREEMPT is not set
+CONFIG_STACKTRACE=y
+# CONFIG_FTRACE is not set
+# CONFIG_STRICT_DEVMEM is not set
\ No newline at end of file
diff --git a/board/chromebook/elm/readme.txt b/board/chromebook/elm/readme.txt
new file mode 100644
index 0000000000..b63e7e8bcf
--- /dev/null
+++ b/board/chromebook/elm/readme.txt
@@ -0,0 +1,56 @@
+Mediatek MT8173 aka Chromebook Elm
+==================================
+
+This file describes booting the Chromebook from an SD card containing
+Buildroot kernel and rootfs, using the original bootloader. This is
+the least invasive way to get Buildroot onto the devices and a good
+starting point.
+
+The bootloader will only boot a kernel from a GPT partition marked
+bootable with cgpt tool from vboot-utils package.
+The kernel image must be signed using futility from the same package.
+The signing part is done by sign.sh script in this directory.
+
+It does not really matter where rootfs is as long as the kernel is able
+to find it, but this particular configuration assumes the kernel is on
+partition 1 and rootfs is on partition 2 of the SD card.
+Make sure to check kernel.args if you change this.
+
+Making the boot media
+---------------------
+Start by configuring and building the images.
+
+	make chromebook_elm_defconfig
+	make menuconfig # if necessary
+	make
+
+The important files are:
+
+	uImage.kpart (kernel and device tree, signed)
+	rootfs.tar
+	bootsd.img (SD card image containing both kernel and rootfs)
+
+Write the image directly to some SD card.
+WARNING: make sure there is nothing important on that card,
+and double-check the device name!
+
+	SD=/dev/mmcblk1		# may be /dev/sdX on some hosts
+	dd if=output/images/bootsd.img of=$SD
+
+Switching to developer mode and booting from SD
+-----------------------------------------------
+Power Chromebook down, then power it up while holding Esc+F3.
+BEWARE: switching to developer mode deletes all user data.
+Create backups if you need them.
+
+While in developer mode, Chromebook will boot into a white screen saying
+"OS verification is off".
+
+Press Ctrl-D at this screen to boot Chromium OS from eMMC.
+Press Ctrl-U at this screen to boot from SD (or USB)
+Press Power to power it off.
+Do NOT press Space unless you mean it.
+This will switch it back to normal mode.
+
+The is no way to get rid of the white screen without re-flashing the bootloader.
+
diff --git a/board/chromebook/elm/sign.sh b/board/chromebook/elm/sign.sh
new file mode 100644
index 0000000000..b1c1ffee40
--- /dev/null
+++ b/board/chromebook/elm/sign.sh
@@ -0,0 +1,41 @@
+#!/bin/sh
+
+# This script creates u-boot FIT image containing the kernel and the DT,
+# then signs it using futility from vboot-utils.
+# The resulting file is called uImage.kpart.
+
+BOARD_DIR=$(dirname $0)/${BOARD_NAME}
+mkimage=$HOST_DIR/bin/mkimage
+futility=$HOST_DIR/bin/futility
+devkeys=$HOST_DIR/share/vboot/devkeys
+
+run() { echo "$@"; "$@"; }
+die() { echo "$@" >&2; exit 1; }
+test -f $BINARIES_DIR/Image  || \
+	die "No kernel image found"
+test -x $mkimage || \
+	die "No mkimage found (host-uboot-tools has not been built?)"
+test -x $futility || \
+	die "No futility found (host-vboot-utils has not been built?)"
+
+# kernel.its references zImage and exynos5250-snow.dtb, and all three
+# files must be in current directory for mkimage.
+run cp $BOARD_DIR/kernel.its $BINARIES_DIR/kernel.its || exit 1
+echo "# entering $BINARIES_DIR for the next command"
+(cd $BINARIES_DIR && run $mkimage -f kernel.its uImage.itb) || exit 1
+
+# futility requires non-empty file to be supplied with --bootloader
+# even if it does not make sense for the target platform.
+echo > $BINARIES_DIR/dummy.txt
+
+run $futility vbutil_kernel \
+	--keyblock $devkeys/kernel.keyblock \
+	--signprivate $devkeys/kernel_data_key.vbprivk \
+	--arch aarch64 \
+	--version 1 \
+	--config $BOARD_DIR/kernel.args \
+	--vmlinuz $BINARIES_DIR/uImage.itb \
+	--bootloader $BINARIES_DIR/dummy.txt \
+	--pack $BINARIES_DIR/uImage.kpart || exit 1
+
+rm -f $BINARIES_DIR/kernel.its $BINARIES_DIR/dummy.txt
-- 
2.25.1

[Buildroot] [PATCH 2/3] boards: chromebook: Move "mksd.sh" out of chromebook snow folder.

[Thomas Petazzoni]

Hello Bilal,

Thanks for your contribution!

On Mon, 21 Sep 2020 23:12:45 +0500
Bilal Wasim <bilalwasim676@gmail.com> wrote:

> The same script is used by Chromebook Elm to generate a bootable
> SD / USB image. Therefore, move the script out of the snow folder
> to one level above (boards/chromebook/snow -> boards/chromebook).
> 
> Update the Chrome snow defconfig to reflect the new location of the
> script.
> 
> Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>
> ---
>  board/chromebook/{snow => }/mksd.sh | 0
>  configs/chromebook_snow_defconfig   | 2 +-
>  2 files changed, 1 insertion(+), 1 deletion(-)
>  rename board/chromebook/{snow => }/mksd.sh (100%)

I fixed up a bit the commit title and commit log, and applied. This
indeed is needed as a pre-requisite to adding the Chromebook Elm
configuration.

Another question: could you see if this mksd.sh script can be dropped
in favor of using genimage to generate the SD card image? Indeed,
genimage now has support for GPT partitions, so I believe it should be
able to generate a working image. Do you think you could have a look at
that ?

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[Buildroot] [PATCH 1/3] configs: Add default configuration for Chromebook Elm.

[Thomas Petazzoni]

Hello,

On Mon, 21 Sep 2020 23:12:44 +0500
Bilal Wasim <bilalwasim676@gmail.com> wrote:

> The architecture of the MT8173 SoC is armv8-a in a big-little config.
> This SoC is supported by the Chrome-OS linux kernel, but the mainline
> support is reasonably good as well (benchmarks / conformance run fine)
> and so that is used. For now, the kernel is 5.9-rc5 which will be uprevd
> to 5.9 once its released.
> 
> The defconfig also lists all the tools (parted, vboot) that are necessary
> to create a bootable image.
> 
> Signed-off-by: Bilal Wasim <bilalwasim676@gmail.com>

The commit title should be:

	configs/chromebook_elm: new defconfig

and it should be squashed with your PATCH 3/3. Indeed as it is, your
PATCH 1/3 alone doesn't build: it depends on files added by PATCH 3/3.

>  configs/chromebook_elm_defconfig | 35 ++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>  create mode 100644 configs/chromebook_elm_defconfig
> 
> diff --git a/configs/chromebook_elm_defconfig b/configs/chromebook_elm_defconfig
> new file mode 100644
> index 0000000000..9b467ec6a8
> --- /dev/null
> +++ b/configs/chromebook_elm_defconfig
> @@ -0,0 +1,35 @@
> +# Architecture
> +BR2_aarch64=y
> +BR2_cortex_a72_a53=y
> +
> +# Filesystem
> +BR2_TARGET_ROOTFS_EXT2=y
> +BR2_TARGET_ROOTFS_EXT2_4=y

You'll need a:

BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_9=y

but this option doesn't exist yet, so we'll have to add it.

Other than that, the defconfig looks good to me.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[Buildroot] [PATCH 3/3] boards: chromebook: Add support of Chromebook Elm

[Thomas Petazzoni]

Hello,

On Mon, 21 Sep 2020 23:12:46 +0500
Bilal Wasim <bilalwasim676@gmail.com> wrote:

>  board/chromebook/elm/kernel.args              |   1 +
>  board/chromebook/elm/kernel.its               |  38 ++
>  board/chromebook/elm/linux-5.9-elm-hdmi.patch | 404 ++++++++++++++++
>  board/chromebook/elm/linux.config             | 453 ++++++++++++++++++
>  board/chromebook/elm/readme.txt               |  56 +++
>  board/chromebook/elm/sign.sh                  |  41 ++
>  6 files changed, 993 insertions(+)

You should add an entry in the DEVELOPERS file to reference the
defconfig and board/chromebook/elm/ directory.


> diff --git a/board/chromebook/elm/linux-5.9-elm-hdmi.patch b/board/chromebook/elm/linux-5.9-elm-hdmi.patch
> new file mode 100644
> index 0000000000..7f549dcc6d
> --- /dev/null
> +++ b/board/chromebook/elm/linux-5.9-elm-hdmi.patch

Please use one file for each patch, instead of concatenating all
patches into one file. The patches should be generated with "git
format-patch".


> diff --git a/board/chromebook/elm/readme.txt b/board/chromebook/elm/readme.txt
> new file mode 100644
> index 0000000000..b63e7e8bcf
> --- /dev/null
> +++ b/board/chromebook/elm/readme.txt
> @@ -0,0 +1,56 @@
> +Mediatek MT8173 aka Chromebook Elm
> +==================================
> +
> +This file describes booting the Chromebook from an SD card containing
> +Buildroot kernel and rootfs, using the original bootloader. This is
> +the least invasive way to get Buildroot onto the devices and a good
> +starting point.
> +
> +The bootloader will only boot a kernel from a GPT partition marked
> +bootable with cgpt tool from vboot-utils package.
> +The kernel image must be signed using futility from the same package.
> +The signing part is done by sign.sh script in this directory.
> +
> +It does not really matter where rootfs is as long as the kernel is able
> +to find it, but this particular configuration assumes the kernel is on
> +partition 1 and rootfs is on partition 2 of the SD card.
> +Make sure to check kernel.args if you change this.
> +
> +Making the boot media
> +---------------------
> +Start by configuring and building the images.
> +
> +	make chromebook_elm_defconfig
> +	make menuconfig # if necessary
> +	make
> +
> +The important files are:
> +
> +	uImage.kpart (kernel and device tree, signed)
> +	rootfs.tar
> +	bootsd.img (SD card image containing both kernel and rootfs)
> +
> +Write the image directly to some SD card.
> +WARNING: make sure there is nothing important on that card,
> +and double-check the device name!
> +
> +	SD=/dev/mmcblk1		# may be /dev/sdX on some hosts
> +	dd if=output/images/bootsd.img of=$SD
> +
> +Switching to developer mode and booting from SD
> +-----------------------------------------------
> +Power Chromebook down, then power it up while holding Esc+F3.
> +BEWARE: switching to developer mode deletes all user data.
> +Create backups if you need them.
> +
> +While in developer mode, Chromebook will boot into a white screen saying
> +"OS verification is off".
> +
> +Press Ctrl-D at this screen to boot Chromium OS from eMMC.
> +Press Ctrl-U at this screen to boot from SD (or USB)
> +Press Power to power it off.
> +Do NOT press Space unless you mean it.
> +This will switch it back to normal mode.
> +
> +The is no way to get rid of the white screen without re-flashing the bootloader.
> +
> diff --git a/board/chromebook/elm/sign.sh b/board/chromebook/elm/sign.sh
> new file mode 100644
> index 0000000000..b1c1ffee40
> --- /dev/null
> +++ b/board/chromebook/elm/sign.sh
> @@ -0,0 +1,41 @@
> +#!/bin/sh
> +
> +# This script creates u-boot FIT image containing the kernel and the DT,
> +# then signs it using futility from vboot-utils.
> +# The resulting file is called uImage.kpart.
> +
> +BOARD_DIR=$(dirname $0)/${BOARD_NAME}
> +mkimage=$HOST_DIR/bin/mkimage
> +futility=$HOST_DIR/bin/futility
> +devkeys=$HOST_DIR/share/vboot/devkeys
> +
> +run() { echo "$@"; "$@"; }
> +die() { echo "$@" >&2; exit 1; }
> +test -f $BINARIES_DIR/Image  || \
> +	die "No kernel image found"
> +test -x $mkimage || \
> +	die "No mkimage found (host-uboot-tools has not been built?)"
> +test -x $futility || \
> +	die "No futility found (host-vboot-utils has not been built?)"
> +
> +# kernel.its references zImage and exynos5250-snow.dtb, and all three

Bad copy paste here :-)

> +# files must be in current directory for mkimage.
> +run cp $BOARD_DIR/kernel.its $BINARIES_DIR/kernel.its || exit 1
> +echo "# entering $BINARIES_DIR for the next command"
> +(cd $BINARIES_DIR && run $mkimage -f kernel.its uImage.itb) || exit 1
> +
> +# futility requires non-empty file to be supplied with --bootloader
> +# even if it does not make sense for the target platform.
> +echo > $BINARIES_DIR/dummy.txt
> +
> +run $futility vbutil_kernel \
> +	--keyblock $devkeys/kernel.keyblock \
> +	--signprivate $devkeys/kernel_data_key.vbprivk \
> +	--arch aarch64 \
> +	--version 1 \
> +	--config $BOARD_DIR/kernel.args \
> +	--vmlinuz $BINARIES_DIR/uImage.itb \
> +	--bootloader $BINARIES_DIR/dummy.txt \
> +	--pack $BINARIES_DIR/uImage.kpart || exit 1
> +
> +rm -f $BINARIES_DIR/kernel.its $BINARIES_DIR/dummy.txt

This script looks very very similar to the one for the snow Chromebook.
The only difference that I could spot is the --arch argument, which is
--arch arm in snow, and --arch aarch64 here.

So, I guess you could easily do a:

if test grep -q ^BR2_arm=y ${BR2_CONFIG}; then
	arch="arm"
else
	arch="aarch64"
fi

or something along those lines.

Other than that, the rest looks good.

Could you take into account those comments, and submit an updated
version?

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com