On 2/20/20 8:05 PM, Ang, Chee Hong wrote:
On 2/20/20 3:27 AM, Ang, Chee Hong wrote:
On 2/19/20 1:25 PM, chee.hong.ang@intel.com wrote: [...]
diff --git a/arch/arm/mach-socfpga/lowlevel_init.S b/arch/arm/mach-socfpga/lowlevel_init.S new file mode 100644 index 0000000..68053a0 --- /dev/null +++ b/arch/arm/mach-socfpga/lowlevel_init.S
This should be some lowlevel_init_64.S to make it clear it's only for arm64 platforms.
OK. It makes sense. Thanks.
@@ -0,0 +1,85 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/*
- Copyright (C) 2019, Intel Corporation */
+#include <asm-offsets.h> +#include <config.h> +#include <linux/linkage.h> +#include <asm/macro.h>
+ENTRY(lowlevel_init)
- mov x29, lr /* Save LR */
+#if defined(CONFIG_GICV2) || defined(CONFIG_GICV3) #ifdef +CONFIG_SPL_ATF
- branch_if_slave x0, 2f
+#else
- branch_if_slave x0, 1f
+#endif
- ldr x0, =GICD_BASE
- bl gic_init_secure
+#ifdef CONFIG_SPL_BUILD
- b 2f
+#else
- b 3f
+#endif
Can't this be done in C code ? Can we reduce the ifdeffery ?
This lowlevel_init function is shared by SPL and U-Boot and they run in slightly different flow.
What does this 'different flow' mean ?
This has something to with multi-cores CPU such as A53. For SPL, we need to make sure the slave CPUs (CPU1/2/3) trapped in a 'place' Where they could be 'activated' by kernel for multi-processor environment. It means the kernel get to 'activate' the slave CPUs from master CPU (CPU0) U-Boot proper only run on master CPU (CPU0). The rest of slave CPUs are trapped in the beginning of SPL waiting to be 'activated' by kernel.
OK, so the secondary CPUs are spinning until the kernel releases them.
In U-Boot proper, only master CPU gets to run this code and it will just do the basic GIC setup and skip the 'trap'. The 'trap' is to prevent the slave CPUs from running the same SPL, ATF and U-Boot code as the master CPU in parallel. Only single core (maser CPU) is needed for bootloaders and firmware.
I would expect all the other SMP platforms solved this issue with secondary CPUs already, so why is agilex special ?