[PATCH v4 2/6] lib: sbi_hsm: handle failure when hart_stop returns SBI_ENOTSUPP

[Yu Chien Peter Lin]

Make use of generic warm-boot path when platform hart_stop callback
returns SBI_ENOTSUPP, in case certain hart can not turn off its
power domain, or it detects some error occured in power management
unit, it can fall through warm-boot flow and wait for interrupt in
sbi_hsm_hart_wait().

Also improves comment in sbi_hsm_hart_wait().

Signed-off-by: Yu Chien Peter Lin <peterlin at andestech.com>
Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
Reviewed-by: Atish Patra <atishp at rivosinc.com>
Reviewed-by: Anup Patel <anup at brainfault.org>
---
 include/sbi/sbi_hsm.h | 8 ++++++--
 lib/sbi/sbi_hsm.c     | 7 +++----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/sbi/sbi_hsm.h b/include/sbi/sbi_hsm.h
index c2a728a4..1170127b 100644
--- a/include/sbi/sbi_hsm.h
+++ b/include/sbi/sbi_hsm.h
@@ -21,8 +21,12 @@ struct sbi_hsm_device {
 	int (*hart_start)(u32 hartid, ulong saddr);
 
 	/**
-	 * Stop (or power-down) the current hart from running. This call
-	 * doesn't expect to return if success.
+	 * Stop (or power-down) the current hart from running.
+	 *
+	 * Return SBI_ENOTSUPP if the hart does not support platform-specific
+	 * stop actions.
+	 *
+	 * For successful stop, the call won't return.
 	 */
 	int (*hart_stop)(void);
 
diff --git a/lib/sbi/sbi_hsm.c b/lib/sbi/sbi_hsm.c
index c0a55054..d4cce4ac 100644
--- a/lib/sbi/sbi_hsm.c
+++ b/lib/sbi/sbi_hsm.c
@@ -116,7 +116,7 @@ static void sbi_hsm_hart_wait(struct sbi_scratch *scratch, u32 hartid)
 	/* Set MSIE and MEIE bits to receive IPI */
 	csr_set(CSR_MIE, MIP_MSIP | MIP_MEIP);
 
-	/* Wait for hart_add call*/
+	/* Wait for state transition requested by sbi_hsm_hart_start() */
 	while (atomic_read(&hdata->state) != SBI_HSM_STATE_START_PENDING) {
 		wfi();
 	};
@@ -228,9 +228,8 @@ void __noreturn sbi_hsm_exit(struct sbi_scratch *scratch)
 		goto fail_exit;
 
 	if (hsm_device_has_hart_hotplug()) {
-		hsm_device_hart_stop();
-		/* It should never reach here */
-		goto fail_exit;
+		if (hsm_device_hart_stop() != SBI_ENOTSUPP)
+			goto fail_exit;
 	}
 
 	/**
-- 
2.34.1