lib: sbi: Ensure coldboot HART supports next privilege mode

The coldboot HART jumps to the next booting stage at the end of
init_coldboot() so it is absolutely necessary for coldboot HART
to support the privilege mode expected by the next booting stage.

We extend the coldboot HART selection in sbi_init() to ensure that
the selected coldboot HART always supports privilege mode specified
in scratch space (i.e. scratch->next_mode). This will further help
us allow E-core (without MMU) on SiFive Unleashed and PolarFire
ICICLE boards to proceed further and wait in HSM STOPPED state.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
index e1a1d96..65d81ba 100644 (file)
--- a/lib/sbi/sbi_init.c
+++ b/lib/sbi/sbi_init.c
@@ -295,6 +295,7 @@ static atomic_t coldboot_lottery = ATOMIC_INITIALIZER(0);
  */
 void __noreturn sbi_init(struct sbi_scratch *scratch)
 {
+       bool next_mode_supported        = FALSE;
        bool coldboot                   = FALSE;
        u32 hartid                      = current_hartid();
        const struct sbi_platform *plat = sbi_platform_ptr(scratch);
@@ -303,7 +304,33 @@ void __noreturn sbi_init(struct sbi_scratch *scratch)
            sbi_platform_hart_invalid(plat, hartid))
                sbi_hart_hang();
 
-       if (atomic_xchg(&coldboot_lottery, 1) == 0)
+       switch (scratch->next_mode) {
+       case PRV_M:
+               next_mode_supported = TRUE;
+               break;
+       case PRV_S:
+               if (misa_extension('S'))
+                       next_mode_supported = TRUE;
+               break;
+       case PRV_U:
+               if (misa_extension('U'))
+                       next_mode_supported = TRUE;
+               break;
+       default:
+               sbi_hart_hang();
+       }
+
+       /*
+        * Only the HART supporting privilege mode specified in the
+        * scratch->next_mode should be allowed to become the coldboot
+        * HART because the coldboot HART will be directly jumping to
+        * the next booting stage.
+        *
+        * We use a lottery mechanism to select coldboot HART among
+        * HARTs which satisfy above condition.
+        */
+
+       if (next_mode_supported && atomic_xchg(&coldboot_lottery, 1) == 0)
                coldboot = TRUE;
 
        if (coldboot)