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[v4,9/9] riscv: Do not initialize PMP on Kendryte SoC

Message ID 20200316004744.209292-10-damien.lemoal@wdc.com (mailing list archive)
State New, archived
Headers show
Series Kendryte k210 SoC boards support | expand

Commit Message

Damien Le Moal March 16, 2020, 12:47 a.m. UTC 
Commit c68a9032299e ("riscv: set pmp configuration if kernel is running
in M-mode") added PMP initialization to M-Mode. While this patch is
valid for any SoC following the ratified riscv specifications, the
Kendryte K210 SoC is based on earlier unstable specifications and does
not seem to support PMP initialization (the SoC crashes if CSR_PMPADDR0
or CSR_PMPCFG0 are accessed).

Since all physical memory access works fine on this SoC without any
explicit PMP initialization, avoid the SoC crash by not touching the
PMP CSRs.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/kernel/head.S | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 52ed11b4fda6..1a5defdc33d2 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -58,11 +58,17 @@  _start_kernel:
 	/* Reset all registers except ra, a0, a1 */
 	call reset_regs
 
-	/* Setup a PMP to permit access to all of memory. */
+	/*
+	 * For M-mode, setup PMP to permit access to all of memory.
+	 * This should however not be done for the  Kendryte K210 SoC as this
+	 * causes a crash (this SoC follows older unstable specification).
+	 */
+#ifndef CONFIG_SOC_KENDRYTE
 	li a0, -1
 	csrw CSR_PMPADDR0, a0
 	li a0, (PMP_A_NAPOT | PMP_R | PMP_W | PMP_X)
 	csrw CSR_PMPCFG0, a0
+#endif
 
 	/*
 	 * The hartid in a0 is expected later on, and we have no firmware