lib: sbi_hsm: Assume a consistent resume address

The suspend code needs to know the resume address for two reasons:
  1) Programming some hardware register or management firmware. Here we
     assume the hardware/firmware maintains its state between suspends,
     so it only needs to be programmed once at startup.
  2) When a non-retentive suspend request ends up being retentive, due
     to lack of hardware support, pending interrupt, or for some other
     reason. However, the behavior here is not platform-dependent, and
     this can be handled in the generic hart suspend function.

Since neither situation requires the platform-level suspend function to
know the resume address, stop passing it to that function. Instead,
handle the non-retentive to retentive situation generically.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>

include/sbi/sbi_hsm.h

@@ -34,9 +34,9 @@ struct sbi_hsm_device {
 	 * the hart resumes normal execution.
 	 *
 	 * For successful non-retentive suspend, the hart will resume from
-	 * specified resume address
+	 * the warm boot entry point.
 	 */
-	int (*hart_suspend)(u32 suspend_type, ulong raddr);
+	int (*hart_suspend)(u32 suspend_type);
 
 	/**
 	 * Perform platform-specific actions to resume from a suspended state.

lib/sbi/sbi_hsm.c

@@ -171,10 +171,10 @@ static int hsm_device_hart_stop(void)
 	return SBI_ENOTSUPP;
 }
 
-static int hsm_device_hart_suspend(u32 suspend_type, ulong raddr)
+static int hsm_device_hart_suspend(u32 suspend_type)
 {
 	if (hsm_dev && hsm_dev->hart_suspend)
-		return hsm_dev->hart_suspend(suspend_type, raddr);
+		return hsm_dev->hart_suspend(suspend_type);
 	return SBI_ENOTSUPP;
 }
 
@@ -319,7 +319,7 @@ int sbi_hsm_hart_stop(struct sbi_scratch *scratch, bool exitnow)
 	return 0;
 }
 
-static int __sbi_hsm_suspend_ret_default(struct sbi_scratch *scratch)
+static int __sbi_hsm_suspend_default(struct sbi_scratch *scratch)
 {
 	/* Wait for interrupt */
 	wfi();
@@ -359,23 +359,6 @@ static void __sbi_hsm_suspend_non_ret_restore(struct sbi_scratch *scratch)
 	csr_write(CSR_MIP, (hdata->saved_mip & (MIP_SSIP | MIP_STIP)));
 }
 
-static int __sbi_hsm_suspend_non_ret_default(struct sbi_scratch *scratch,
-					     ulong raddr)
-{
-	void (*jump_warmboot)(void) = (void (*)(void))scratch->warmboot_addr;
-
-	/* Wait for interrupt */
-	wfi();
-
-	/*
-	 * Directly jump to warm reboot to simulate resume from a
-	 * non-retentive suspend.
-	 */
-	jump_warmboot();
-
-	return 0;
-}
-
 void sbi_hsm_hart_resume_start(struct sbi_scratch *scratch)
 {
 	int oldstate;
@@ -473,17 +456,28 @@ int sbi_hsm_hart_suspend(struct sbi_scratch *scratch, u32 suspend_type,
 		__sbi_hsm_suspend_non_ret_save(scratch);
 
 	/* Try platform specific suspend */
-	ret = hsm_device_hart_suspend(suspend_type, scratch->warmboot_addr);
+	ret = hsm_device_hart_suspend(suspend_type);
 	if (ret == SBI_ENOTSUPP) {
 		/* Try generic implementation of default suspend types */
-		if (suspend_type == SBI_HSM_SUSPEND_RET_DEFAULT) {
+		if (suspend_type == SBI_HSM_SUSPEND_RET_DEFAULT ||
-			ret = __sbi_hsm_suspend_ret_default(scratch);
+		    suspend_type == SBI_HSM_SUSPEND_NON_RET_DEFAULT) {
-		} else if (suspend_type == SBI_HSM_SUSPEND_NON_RET_DEFAULT) {
+			ret = __sbi_hsm_suspend_default(scratch);
-			ret = __sbi_hsm_suspend_non_ret_default(scratch,
-						scratch->warmboot_addr);
 		}
 	}
 
+	/*
+	 * The platform may have coordinated a retentive suspend, or it may
+	 * have exited early from a non-retentive suspend. Either way, the
+	 * caller is not expecting a successful return, so jump to the warm
+	 * boot entry point to simulate resume from a non-retentive suspend.
+	 */
+	if (ret == 0 && (suspend_type & SBI_HSM_SUSP_NON_RET_BIT)) {
+		void (*jump_warmboot)(void) =
+			(void (*)(void))scratch->warmboot_addr;
+
+		jump_warmboot();
+	}
+
 fail_restore_state:
 	/*
 	 * We might have successfully resumed from retentive suspend