Hi, On Tue, May 22, 2018 at 10:02:50AM +0200, Pali Rohár wrote: > Hi! I remember that in time of migration from platform board code to > device tree structures there appeared some bug which caused that > sometimes display were not initialized. And somebody figured out that > display initialization is failing when some other SPI devices are > initialized before or after display... This behavior was observed only > on real N900 hardware, not in qemu. Touchscreen needs to be initialized before display. This is documented in the DTS, see arch/arm/boot/dts/omap3-n900.dts: * For some reason, touchscreen is necessary for screen to work at * all on real hw. It works well without it on emulator. * * Also... order in the device tree actually matters here. > Real reason was never explained. In old platform board code there was > hardcoded order of SPI devices in which initialization happened. And in > device tree it is probably in (pseudo)-random order. Enabling/disabling > various config option can affect some timings and order in which kernel > starts probing and initializing devices... The issue was also somewhat present with platform/board code, see e.g. commit e65f131a14726e5f1b880a528271a52428e5b3a5. My device worked with v4.17-rc1 (haven't found time to test newer kernels), but if you say the probe order is random then we must find some proper way to express the dependency. A. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
