fbtft + device tree on sam9g25 cpu ssd1331 mirrored display

[mani009]

Hello everybody,

I have an arietta g25 with ssd1331 oled display with mirrored display.

I have start the Kernel modul with this changes :

modprobe fbtft_device name=ssd1331 busnum=32766 gpios=reset:67,dc:68 speed=20000000

dmesg output :

fbtft: module is from the staging directory, the quality is unknown, you have been warned. fbtft_device: module is from the staging directory, the quality is unknown, you have been warned. fbtft_device: SPI devices registered: fbtft_device: 'fb' Platform devices registered: fbtft_device: GPIOS used by 'ssd1331': fbtft_device: 'reset' = GPIO67 fbtft_device: 'dc' = GPIO68 fbtft_device: SPI devices registered: fbtft_device: fb_ssd1331 spi32766.0 20000kHz 8 bits mode=0x03 fb_ssd1331: module is from the staging directory, the quality is unknown, you have been warned. graphics fb0: fb_ssd1331 frame buffer, 96x64, 12 KiB video memory, 4 KiB DMA buffer memory, fps=21, spi32766.0 at 20 MHz

I have start die Module again with rotate option and have the same problem : modprobe fbtft_device name=ssd1331 busnum=32766 gpios=reset:67,dc:68 speed=20000000 rotate=270

dts:

            spi1: spi@f0004000 {
            status = "okay";
            cs-gpios = <&pioA 8 0>;

                    /*device@1 {
                    compatible = "spidev";
                    spi-max-frequency = <50000000>;     // 5 MHz
                    reg = <1>;
                    };*/
        };

Can anyone help me what i`am doing wrong ???

[irfansehic]

What is the problem? I also use sam9g25 (Arietta G25 by Acme).

[mani009]

Hello irfansehic,

the problem is the display is mirrored . I take a photo form the display , but at the moment i have borrowed my arietta board.

And the Rotate option doesn`t change anything.

[notro]

fb_ssd1331 does not support rotation (no fbtftops.set_var function). A mirrored display means that the default init sequence does not match your display. From the datasheet I can see that register 0xA0 controls mirroring. Try changing the value in the driver init_display() function:

        write_reg(par, 0xa0, 0x70 | (par->bgr << 2)); /* Set Colour Depth */

Driver: http://lxr.free-electrons.com/source/drivers/staging/fbtft/fb_ssd1331.c Datasheet page 37: http://www.adafruit.com/datasheets/SSD1331_1.2.pdf

[mani009]

Thanks a lot ,

I'll try it and write back as soon as possible .

[quinte17]

and yes changing the initialisation helps a bit. atm using kernel 4.1 with dts.

                        spi1: spi@f0004000 {
                                status = "okay";
                                cs-gpios = <&pioA 8 0>;

                                device@0 {
                                        rotate = <270>;
                                        bgr;
                                        fps = <30>;
                                        compatible = "solomon,ssd1331";
                                        spi-max-frequency = <20000000>;
                                        reg = <0>;
                                        regwidth = <8>;
                                        buswidth = <8>;
                                        verbose = <3>;
                                        reset-gpios = <&pioC 3 0>; /* PC3 - J4.33 */
                                        dc-gpios = <&pioC 4 0>;    /* PC4 - J4.31 */
                                };
                        };

the white bottom is some random painting. memory not initialized or something. and the mirrored text on the right is some old value from the boot before

[quinte17]

without the rotate option in the dts and with the flip bit for rotation set, the display seems working, at least for console.

                        spi1: spi@f0004000 {
                                status = "okay";
                                cs-gpios = <&pioA 8 0>;

                                device@0 {
                                        bgr;
                                        fps = <30>;
                                        compatible = "solomon,ssd1331";
                                        spi-max-frequency = <20000000>;
                                        reg = <0>;
                                        regwidth = <8>;
                                        buswidth = <8>;
                                        verbose = <3>;
                                        reset-gpios = <&pioC 3 0>; /* PC3 - J4.33 */
                                        dc-gpios = <&pioC 4 0>;    /* PC4 - J4.31 */
                                };
                        };

[quinte17]

still having trouble with displaying bitmaps. is there an example file anywhere which can be dd'ed to fb0?

[notro]

I have used this from time to time:

git clone https://git.kernel.org/pub/scm/linux/kernel/git/geert/fbtest.git
cd fbtest
make
./fbtest -f /dev/fb1

[quinte17]

notro, thx that worked like a charm. is it possible to add an option to the devicetree to be able to set that bit? how could a generic way look like?

# changed line
write_reg(par, 0xa0, 0x02 | 0x70 | (par->bgr << 2)); /* Set Colour Depth */

[notro]

There is an option already to change the whole initialisation: init=<..>; See https://github.com/raspberrypi/linux/blob/rpi-4.0.y/arch/arm/boot/dts/overlays/mz61581-overlay.dts#L67

Rules: A command byte must be or'ed with 0x1000000 A delay is or'ed with 0x2000000

The function fbtft_init_display_dt is responsible for parsing the init property.

[quinte17]

so as i understand it: if an init-section exists then it is executed instead of the static int init_display(struct fbtft_par *par)

does that also mean that some options in the device-tree, which are only handled in the .. init_display .., wont have any effect anymore? so if someone wants to have that option set he has to manually change the init-sequence of the devicetree.

[quinte17]

notro, thx again. the init section in the dts is something i think i like. i believe you can close this issue now. for completeness the dts part:

            spi1: spi@f0004000 {
                status = "okay";
                cs-gpios = <&pioA 8 0>;

                device@0 {
                    fps = <30>;
                    compatible = "solomon,ssd1331";
                    spi-max-frequency = <20000000>;
                    reg = <0>;
                    regwidth = <8>;
                    buswidth = <8>;
                    verbose = <3>;
                    reset-gpios = <&pioC 3 0>; /* PC3 - J4.33 */
                    dc-gpios = <&pioC 4 0>;    /* PC4 - J4.31 */

                    init = <0x10000ae /* Display Off */
                        0x10000a0 0x72 /* Set Colour Depth and left to right */
                        0x10000a0 0x72 /* RGB colour */
                        0x10000a1 0x00 /* Set Display Start Line */
                        0x10000a2 0x00 /* Set Display Offset */
                        0x10000a4 /* NORMALDISPLAY */
                        0x10000a8 0x3f /* Set multiplex */
                        0x10000ad 0x8e /* Set master */
                         /* 0x10000b0 0x0b  Set power mode */
                        0x10000b1 0x31 /* Precharge */
                        0x10000b3 0xf0 /* Clock div */
                        0x100008a 0x64 /* Precharge A */
                        0x100008b 0x78 /* Precharge B */
                        0x100008c 0x64 /* Precharge C */
                        0x10000bb 0x3a /* Precharge level */
                        0x10000be 0x3e /* vcomh */
                        0x1000087 0x06 /* Master current */
                        0x1000081 0x91 /* Contrast A */
                        0x1000082 0x50 /* Contrast B */
                        0x1000083 0x7d /* Contrast C */
                        0x10000af /* Set Sleep Mode Display On */
                        >;
                };
            };

[denghongcai]

@notro I faced the same problem with @quinte17 . how to rewrite init sequence using modprobe fbtft_device name=ssd1331 gpios=reset:8,dc:7 init=? command instead of dts? for example, 0x10000a0 0x72 equals to what? (sorry, i'm a noob of driver)

[notro]

0x10000a0 0x72

init=-1,0xa0,0x72,-1,reg2,val,...,-3

See: https://github.com/notro/fbtft/wiki/fbtft_device#parameters