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From 33020d03596ae7767f278716ba539589b316299e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
Date: Sun, 27 Mar 2022 18:54:17 +0200
Subject: [PATCH] overlays/rpi-display: Add support for DRM driver
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Add a "drm" parameter that enables use of the drm/mi0283qt driver instead
of fbtft/fb_ili9341. Also add a "backlight-pwm" parameter that can be used
with the "drm" parameter.
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
arch/arm/boot/dts/overlays/README | 26 +++++++-
.../boot/dts/overlays/rpi-display-overlay.dts | 61 ++++++++++++++++++-
2 files changed, 84 insertions(+), 3 deletions(-)
--- a/arch/arm/boot/dts/overlays/README
+++ b/arch/arm/boot/dts/overlays/README
@@ -2913,14 +2913,36 @@ Params: <None>
Name: rpi-display
Info: RPi-Display - 2.8" Touch Display by Watterott
+ Linux has 2 drivers that support this display and this overlay supports
+ both.
+
+ Examples:
+ fbtft/fb_ili9341: dtoverlay=rpi-display
+ drm/mi0283qt: dtoverlay=rpi-display,drm,backlight-pwm,rotate=180
+
+ Some notable differences with the DRM driver compared to fbtft:
+ - The display is turned on when it's first used and not on driver load
+ as with fbtft. So if nothing uses the display it stays off.
+ - Can run with a higher SPI clock increasing framerate. This is possible
+ since the driver avoids messing up the controller configuration due to
+ transmission errors by running config commands at 10MHz and only pixel
+ data at full speed (occasional pixel glitch might occur).
+ - PWM backlight is supported.
+
Load: dtoverlay=rpi-display,<param>=<val>
Params: speed Display SPI bus speed
rotate Display rotation {0,90,180,270}
- fps Delay between frame updates
- debug Debug output level {0-7}
+ fps Delay between frame updates (fbtft only)
+ debug Debug output level {0-7} (fbtft only)
xohms Touchpanel sensitivity (X-plate resistance)
swapxy Swap x and y axis
backlight Change backlight GPIO pin {e.g. 12, 18}
+ (fbtft only)
+ drm Use DRM/KMS driver mi0283qt instead of fbtft.
+ Set the SPI clock to 70MHz.
+ This has to be the first parameter.
+ backlight-pwm Use pwm for backlight (drm only). NB: Disables
+ audio headphone output as that also uses PWM.
Name: rpi-ft5406
--- a/arch/arm/boot/dts/overlays/rpi-display-overlay.dts
+++ b/arch/arm/boot/dts/overlays/rpi-display-overlay.dts
@@ -78,14 +78,73 @@
};
};
};
+
+ fragment@10 {
+ target = <&rpidisplay>;
+ __dormant__ {
+ backlight = <&backlight_gpio>;
+ };
+ };
+
+ fragment@11 {
+ target-path = "/";
+ __dormant__ {
+ backlight_gpio: backlight_gpio {
+ compatible = "gpio-backlight";
+ gpios = <&gpio 18 0>; /* GPIO_ACTIVE_HIGH */
+ };
+ };
+ };
+
+ fragment@20 {
+ target = <&rpidisplay>;
+ __dormant__ {
+ backlight = <&backlight_pwm>;
+ };
+ };
+
+ fragment@21 {
+ target-path = "/";
+ __dormant__ {
+ backlight_pwm: backlight_pwm {
+ compatible = "pwm-backlight";
+ brightness-levels = <0 6 8 12 16 24 32 40 48 64 96 128 160 192 224 255>;
+ default-brightness-level = <16>;
+ pwms = <&pwm 0 200000>;
+ };
+ };
+ };
+
+ fragment@22 {
+ target = <&pwm>;
+ __dormant__ {
+ assigned-clock-rates = <1000000>;
+ status = "okay";
+ };
+ };
+
+ fragment@23 {
+ target = <&audio>;
+ __dormant__ {
+ brcm,disable-headphones;
+ };
+ };
+
__overrides__ {
speed = <&rpidisplay>,"spi-max-frequency:0";
- rotate = <&rpidisplay>,"rotate:0";
+ rotate = <&rpidisplay>,"rotate:0", /* fbtft */
+ <&rpidisplay>,"rotation:0"; /* drm */
fps = <&rpidisplay>,"fps:0";
debug = <&rpidisplay>,"debug:0";
xohms = <&rpidisplay_ts>,"ti,x-plate-ohms;0";
swapxy = <&rpidisplay_ts>,"ti,swap-xy?";
backlight = <&rpidisplay>,"led-gpios:4",
<&rpi_display_pins>,"brcm,pins:0";
+ drm = <&rpidisplay>, "compatible=multi-inno,mi0283qt",
+ <&rpidisplay>, "spi-max-frequency:0=70000000",
+ <&rpidisplay>, "reset-gpios:8=0", /* GPIO_ACTIVE_HIGH */
+ <0>, "+10+11";
+ backlight-pwm = <0>, "-10-11+20+21+22+23",
+ <&rpi_display_pins>, "brcm,function:0=2"; /* Alt5 */
};
};
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