[PATCH 1/4] riscv: Call early_ioremap_setup() before parsing the DTB

[Chen Pei]

early_ioremap_setup() fills in the slot_virt[] array whose entries the
return value of early_ioremap()/early_memremap() is composed from.  On
RISC-V it ran after parse_dtb(), so an early_memremap() reached from
the device tree scan returned "offset + 0" -- NULL for a page aligned
address -- and the caller could only report a mapping failure.  This
stayed latent because nothing reached from parse_dtb() asked for an
early mapping before; the DT based kexec handover parsing is the first
such caller, as kho_populate() maps the handover FDT and the scratch
descriptor array with early_memremap().

Move the call to the top of setup_arch(), which is how arm64 and x86
already order it (early_fixmap_init()/early_ioremap_init() before
setup_machine_fdt()/parse_setup_data()).  The BTMAP window is mapped
into early_pg_dir by setup_vm(), and RISC-V neither calls
early_ioremap_reset() nor defines __late_set_fixmap(), so the virtual
addresses stay identical across the switch to the final page tables
and nothing else in setup_arch() depends on the previous ordering.

Signed-off-by: Chen Pei <cp0613 at linux.alibaba.com>
---
 arch/riscv/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index d79f99b86033..45e2ef9d32fa 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -308,12 +308,12 @@ extern void __init init_rt_signal_env(void);
 
 void __init setup_arch(char **cmdline_p)
 {
+	early_ioremap_setup();
 	parse_dtb();
 	setup_initial_init_mm(_stext, _etext, _edata, _end);
 
 	*cmdline_p = boot_command_line;
 
-	early_ioremap_setup();
 	sbi_init();
 	jump_label_init();
 	parse_early_param();
-- 
2.50.1