RX and TX interrupt bits were reversed, resulting in an endless sequence
of serial interupts in the emulated system and the following repeated
error message when booting Linux.
serial8250: too much work for irq61
This results in a boot failure most of the time.
Qemu command line used to reproduce the problem:
qemu-system-aarch64 -M raspi3 -m 1024 \
-kernel arch/arm64/boot/Image \
--append "rdinit=/sbin/init console=ttyS1,115200"
-initrd rootfs.cpio \
-dtb arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dtb \
-nographic -monitor null -serial null -serial stdio
This is with arm64:defconfig. The root file system was generated using
buildroot.
NB that this error likely arises from an erratum in the
BCM2835 datasheet where the TX and RX bits were swapped
in the AU_MU_IER_REG description (but correct for IIR):
https://elinux.org/BCM2835_datasheet_errata#p12
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 1529355846-25102-1-git-send-email-linux@roeck-us.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: added NB about datasheet]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
65e9f27f22