[PATCH v6] lib:utils:irqchip: Check before initializing imsic.

[Cheng Yang]

The current mlevel imsic check is only for the platform, which
may cause hart without imsic in the platform to trigger an
illegal instruction exception when initializing imsic. For
example, the platform contains a management hart that only
supports wired interrupts.

This patch will check if each hart supports Smaia extension
before doing imsic initialization to avoid triggering illegal
instruction exceptions.

Signed-off-by: Cheng Yang <yangcheng.work at foxmail.com>
Changes V5 -> V6:
  - Use csr_read_allowed instead of bitmap to simplify checking if hart supports Imsic, suggestion from Anup.
Changes V4 -> V5:
  - Fixed the issue where patch cannot be applied due to the editor automatically removing trailing spaces.
Changes V3 -> V4:
  - Rebase to the latest master branch.
Changes V2 -> V3:
  - Trailing whitespace.
  - Replace platform.hart_index2id to generic_hart_index2id.
Changes V1 -> V2:
  - Add the processing of plat->hart_index2id be NULL in fdt_check_imsic_mlevel.
---
 lib/utils/irqchip/imsic.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/utils/irqchip/imsic.c b/lib/utils/irqchip/imsic.c
index f2a35c6..fad1beb 100644
--- a/lib/utils/irqchip/imsic.c
+++ b/lib/utils/irqchip/imsic.c
@@ -12,6 +12,7 @@
 #include <sbi/riscv_io.h>
 #include <sbi/riscv_encoding.h>
 #include <sbi/sbi_console.h>
+#include <sbi/sbi_csr_detect.h>
 #include <sbi/sbi_domain.h>
 #include <sbi/sbi_ipi.h>
 #include <sbi/sbi_irqchip.h>
@@ -222,6 +223,7 @@ static void imsic_local_eix_update(unsigned long base_id,
 
 void imsic_local_irqchip_init(void)
 {
+	struct sbi_trap_info trap = { 0 };
 	/*
 	 * This function is expected to be called from:
 	 * 1) nascent_init() platform callback which is called
@@ -231,6 +233,11 @@ void imsic_local_irqchip_init(void)
 	 *    in boot-up path.
 	 */
 
+	/* If Smaia not available then do nothing */
+	csr_read_allowed(CSR_MTOPI, (ulong)&trap);
+	if (trap.cause)
+		return;
+
 	/* Setup threshold to allow all enabled interrupts */
 	imsic_csr_write(IMSIC_EITHRESHOLD, IMSIC_ENABLE_EITHRESHOLD);
 
-- 
2.34.1