RISC-V: S-Mode: propagate Hart ID

Unlike other architectures we support, Linux must apparently be
booted on all cores by the bootloader. To achieve this, the bootloaders
running on the multiple cores synchronize via IPIs.

We will get there eventually, but for now, let's restrict barebox
to boot Linux on a single core. S-Mode firmware is passed hart (core) id
in a0. This is propagated via the thread pointer register, which is
unused by GCC and made available as:

 - cpuinfo output when running in S-Mode
 - $global.hartid
 - a0 when booting via bootm
 - /chosen/boot-hartid fixup: will come in handy when we gain EFI
   loading support
 - single /cpus/*/reg: All other CPU nodes are deleted via fixup

For M-Mode, we can query hart id via CSR. It's unknown whether erizo
supports it and we don't yet have exception support to handle it not
being available, so changes are only done for S-Mode for now.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20210619045055.779-6-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 18 insertions, 1 deletions

diff --git a/common/oftree.c b/common/oftree.c
index 5eaa63ad7e..1fcc5277c5 100644
--- a/common/oftree.c
+++ b/common/oftree.c
@@ -232,7 +232,24 @@ static int of_fixup_bootargs(struct device_node *root, void *unused)
 			return err;
 	}
 
-	return of_fixup_bootargs_bootsource(root, node);
+	err = of_fixup_bootargs_bootsource(root, node);
+	if (err)
+		return err;
+
+	if (IS_ENABLED(CONFIG_RISCV)) {
+		const char *hartid;
+
+		hartid = getenv("global.hartid");
+		if (hartid) {
+			unsigned long id;
+
+			err = kstrtoul(hartid, 10, &id);
+			if (!err)
+				err = of_property_write_u32(node, "boot-hartid", id);
+		}
+	}
+
+	return err;
 }
 
 static int of_register_bootargs_fixup(void)