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Diffstat (limited to 'results/scraper/launchpad-without-comments/1733720')
| -rw-r--r-- | results/scraper/launchpad-without-comments/1733720 | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/results/scraper/launchpad-without-comments/1733720 b/results/scraper/launchpad-without-comments/1733720 new file mode 100644 index 00000000..93f4d1b3 --- /dev/null +++ b/results/scraper/launchpad-without-comments/1733720 @@ -0,0 +1,55 @@ +raspi2 with multiple CPU's #1 + +Greetings, + +I am running a small program for raspi2 (from http://wiki.osdev.org/ARM_RaspberryPi_Tutorial_C). + +This code writes "Hello World", but the output ir repeated 4 times. + +My thought was that this is emulating a 4 cpu core system. + +However, when I check the MPIDR registed for CPU number, it always returns 1. + +I git cloned github.com/qemu/qemu.git, made & installed on Acer ARM CB5-311 under Crouton/ubuntu. + + +./qemu.sh +1111 + +Linux:armv7l: ~/Downloads/RaspiTest/BareBones >>> uname -a +Linux localhost 3.10.18 #1 SMP Mon Nov 13 16:34:10 PST 2017 armv7l armv7l armv7l GNU/Linux + +Linux:armv7l: ~/Downloads/RaspiTest/BareBones >>> qemu-system-arm --version +QEMU emulator version 2.10.91 (v2.11.0-rc1-dirty) +Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers + +===== +static inline uint32_t read_mpdir(void) +{ + uint32_t id; + + asm volatile("mrc p15, 0, %[id], c0, c0, 0 @ read MIDR\n\t" + : [id] "=r" (id)); + return id; +} +====== +void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags) +{ + // Declare as unused + (void) r0; + (void) r1; + (void) atags; + + uint32_t cpu_id; + + cpu_id = read_mpdir() & 0x03; + + uart_putc( "01234"[cpu_id] ); /* output is "1111" */ + + if (cpu_id == 0) { /* code never executes 8^( */ } + +====== qemu.sh +qemu-system-arm -m 256 -M raspi2 -no-reboot -serial stdio -kernel myos.elf + +Thanks much, +-KenD \ No newline at end of file |