Error opening /dev/fb0 on i.Mx8QXP

kailas_kharse — Tue, 27 Oct 2020 10:12:40 GMT

Hello,

We are using i.Mx8QXP C0 Custom Board, we are only using the Flex-SPI interface and LVDS0 Interface along with eMMC Card. We don't have any other peripheral on our board, we have leaveraged the design from i.MX8QXP MEK Baord. Following are the changes w.r.t. MEK.

1.Changing mini-SAS connector to Horizontal part
2.Removing voltage translator U203,
3.Adding pullup to MIPI_DSI0_EN (J1.A11 pin)
4.Removing 12V power to connector, changing power rails as per load switch.

We are using "imx-yocto-L5.4.24_2.1.0" Yocto Build, I am alble to get the display in u-boot by following modifications.

U-Boot:

File: /arch/arm/dts/fsl-imx8qxp-mek.dts
Changes:

lvds-to-hdmi-bridge@4c {
compatible = "ite,it6263";
reg = <0x4c>;
- reset-gpios = <&pca9557_a 6 GPIO_ACTIVE_LOW>;
+ /*reset-gpios = <&pca9557_a 6 GPIO_ACTIVE_LOW>;*/

Just by commenting the reset gpio, we are able to get the splash screen in U-boot. But I have also done the following changes in Kernel DTS files as below for LVDS.

Kernel DTS File: arch/arm64/boot/dts/freescale/imx8x-mek.dtsi
Chantes:

pinctrl_i2c0_mipi_lvds0: mipi_lvds0_i2c0_grp {
fsl,pins = <
                IMX8QXP_MIPI_DSI0_I2C0_SCL_MIPI_DSI0_I2C0_SCL 0xc6000020
                IMX8QXP_MIPI_DSI0_I2C0_SDA_MIPI_DSI0_I2C0_SDA 0xc6000020
                IMX8QXP_MIPI_DSI0_GPIO0_01_LSIO_GPIO1_IO28 0x00000020
               /*IMX8QXP_MIPI_DSI0_GPIO0_01_LSIO_GPIO1_IO28 0x00000020*/
         >;
};

Also I have verified that all the config required for LVDS, LDB, FB, are present and enabled.

Still I am getting the below error: (Boot Logs Snippet)

[ 5.475066] pwm-backlight lvds_backlight@0: lvds_backlight@0 supply power not found, using dummy regulator
[ 5.486216] pwm-backlight lvds_backlight@1: lvds_backlight@1 supply power not found, using dummy regulator
[ 5.502236] dpu-core 56180000.dpu: driver probed
[ 5.508739] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 5.515390] [drm] No driver support for vblank timestamp query.
[ 5.521402] imx-drm display-subsystem: bound imx-drm-dpu-bliteng.2 (ops dpu_bliteng_ops)
[ 5.529878] imx-drm display-subsystem: bound imx-dpu-crtc.0 (ops dpu_crtc_ops)
[ 5.537478] imx-drm display-subsystem: bound imx-dpu-crtc.1 (ops dpu_crtc_ops)
[ 5.545034] imx-drm display-subsystem: failed to bind bus@56220000:ldb@562210e0 (ops imx8qxp_ldb_ops): -517
[ 5.555018] imx-drm display-subsystem: master bind failed: -517

[ 5.828314] i2c i2c-20: LPI2C adapter registered
[ 5.834131] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 5.840765] [drm] No driver support for vblank timestamp query.
[ 5.846771] imx-drm display-subsystem: bound imx-drm-dpu-bliteng.2 (ops dpu_bliteng_ops)
[ 5.855056] imx-drm display-subsystem: bound imx-dpu-crtc.0 (ops dpu_crtc_ops)
[ 5.862443] imx-drm display-subsystem: bound imx-dpu-crtc.1 (ops dpu_crtc_ops)
[ 5.869989] imx-drm display-subsystem: failed to bind bus@56220000:ldb@562210e0 (ops imx8qxp_ldb_ops): -517
[ 5.879983] imx-drm display-subsystem: master bind failed: -517

On Debug console when I use "psplash" command I am getting "Error Operning /dev/fb0"

Can you please suggest tell that what are the changes needed to resolve this issue?

Thanks & Regards,

Kailas K.

Re: Error opening /dev/fb0 on i.Mx8QXP

kailas_kharse — Tue, 27 Oct 2020 10:55:53 GMT

Hello Missed to add below changes also in above message,

I have also commented the Reset PIN in DTS:

Kernel DTS File: arch/arm64/boot/dts/freescale/imx8x-mek.dtsi
Chantes:

lvds_bridge0: lvds-to-hdmi-bridge@4c {
compatible = "ite,it6263";
reg = <0x4c>;
//reset-gpios = <&pca9557_a 6 GPIO_ACTIVE_LOW>;

port {
it6263_0_in: endpoint {
remote-endpoint = <&lvds0_out>;
};
};
};

Thanks & Regards,
Kailas K.

Re: Error opening /dev/fb0 on i.Mx8QXP

igorpadykov — Wed, 28 Oct 2020 01:29:32 GMT

Hi Kailas

for "Error opening /dev/fb0" one can consider sect.6.2.2 Frame Buffer i.MX Linux Reference Manual

"Frame buffer drivers are supported for i.MX 6 and i.MX 7 but not for i.MX 8."

Best regards
igor

Re: Error opening /dev/fb0 on i.Mx8QXP

kailas_kharse — Wed, 28 Oct 2020 04:40:04 GMT

Hello Igor,

I am able to get the display on i.Mx8QXP MEK Baord, but I am facing issue on custom board with the only above changes mentioned. In MEK is am able to get /dev/fb0 but for custom board I am facing issue.

Can you please tell what are the things required to be considered?

Thanks & Regards,

Kailas K.

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