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https://github.com/AsahiLinux/u-boot
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This patch adds code to shutdown secondary cores. When U-boot comes up, all secondary cores appear powered on, which is undesirable and causes side effects while initializing these cores in kernel. Secondary core power down happens in following steps: Step-1: After Exynos power-on, primary core starts executing first. Step-2: In iROM code every core has to check 2 flags i.e. addresses 0x02020028 & 0x02020004. Step-3: Initially 0x02020028 is 0 for all cores and 0x02020004 has a jump address for primary core and 0 for all secondary cores. Step-4: Therefore, primary core follows normal iROM execution and jumps to BL1 eventually, whereas all secondary cores enter WFE. Step-5: When primary core comes into function secondary_cores_configure, it puts pointer to function power_down_core into 0x02020004 and provides DSB and SEV for all cores so that they may come out of WFE and jump to power_down_core function. Step-6: And ultimately because of power_down_core all secondary cores shut-down. Signed-off-by: Kimoon Kim <kimoon.kim@samsung.com> Signed-off-by: Akshay Saraswat <akshay.s@samsung.com> Signed-off-by: Minkyu Kang <mk7.kang@samsung.com> |
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