waveshare35a works with dtoverlay on kernel 5.0, but not on kernel 5.3 on a rpi 3b+?

[satmandu]

It appears the dt overlays are being loaded, but the screen doesn't do anything when I boot on 5.3.

There's a ticket open https://github.com/raspberrypi/linux/issues/3263 where it is suggested that the overlays are being loaded correctly.

Is there an issue with 5.3 and using displays with fbtft?

config.txt command is:

dtoverlay=waveshare35a:rotate=270,speed=21000000,debug=1

[notro]

There was changes to the fbtft gpiop handling in 5.3-rc1 that was only compile tested so it broke stuff. I see there's been some fixes in 5.3-rc4 to rectify this. Problem commit: Staging: fbtft: Switch to the gpio descriptor interface History: https://github.com/torvalds/linux/commits/master/drivers/staging/fbtft

Maybe there's still fallout, I don't know. Currently fbtft is unmaintained, it's listed as Orphan in MAINTAINERS

[satmandu]

I tried building 5.4's fbtft as a module for 5.3.x, and have the dtoverlay being loaded with https://github.com/swkim01/waveshare-dtoverlays/blob/master/waveshare35a.dts modified so thaat

                                reset-gpios = <&gpio 25 0>;
                                dc-gpios = <&gpio 24 0>;

is now

                                reset-gpios = <&gpio 25 1>;
                                dc-gpios = <&gpio 24 1>;

(since apparently that may get flipped in newer fbtft.)

That dtb still loads fine in 4.19 but doesn't do anything in anything newer.

[satmandu]

The winning combo appears to be modifying https://github.com/swkim01/waveshare-dtoverlays/blob/master/waveshare35a.dts thus:

--- waveshare35a.dts    2019-09-30 09:17:06.000000000 -0400
+++ waveshare35a.dts 2019-10-30 15:23:48.000000000 -0400
@@ -54,7 +54,7 @@
                                fps = <30>;
                                buswidth = <8>;
                                regwidth = <16>;
-                               reset-gpios = <&gpio 25 0>;
+                               reset-gpios = <&gpio 25 1>;
                                dc-gpios = <&gpio 24 0>;
                                debug = <0>;

@@ -81,7 +81,7 @@
                                spi-max-frequency = <2000000>;
                                interrupts = <17 2>; /* high-to-low edge triggered */
                                interrupt-parent = <&gpio>;
-                               pendown-gpio = <&gpio 17 0>;
+                               pendown-gpio = <&gpio 17 1>;
                                ti,x-plate-ohms = /bits/ 16 <60>;
                                ti,pressure-max = /bits/ 16 <255>;

Additionally I had to make sure that for the kernel config this was set to module: CONFIG_SPI_BCM2835AUX=m

and then also compile the linux 5.4 series fbtft modules.