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bcm2835_aux: Swap RX and TX interrupt assignments

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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>
This commit is contained in:
Guenter Roeck 2018-07-16 17:18:42 +01:00 committed by Peter Maydell
parent cccf96c3d4
commit 65e9f27f22
1 changed files with 2 additions and 2 deletions
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4
hw/char/bcm2835_aux.c
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@ -39,8 +39,8 @@
#define AUX_MU_BAUD_REG 0x68 #define AUX_MU_BAUD_REG 0x68
/* bits in IER/IIR registers */ /* bits in IER/IIR registers */
#define TX_INT 0x1 #define RX_INT 0x1
#define RX_INT 0x2 #define TX_INT 0x2
static void bcm2835_aux_update(BCM2835AuxState *s) static void bcm2835_aux_update(BCM2835AuxState *s)
{ {