[PATCH 2/5] ARM: trusted_foundations: fallback when TF support is missing

From: Alexandre Courbot
Date: Tue Jan 21 2014 - 05:10:50 EST

When Trusted Foundations is detected as present on the system, but
Trusted Foundations support is not built into the kernel, the kernel
used to issue a panic very early during boot, leaving little clue to the
user as to what is going wrong.

It turns out that even without TF support built-in, the kernel can boot
on a TF-enabled system provided that SMP and cpuidle are disabled. This
patch does this and continue booting on one CPU, leaving the user with a
usable (however degraded) system.

Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
arch/arm/include/asm/trusted_foundations.h | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/trusted_foundations.h b/arch/arm/include/asm/trusted_foundations.h
index 997862fd5d77..b5f7705abcb0 100644
--- a/arch/arm/include/asm/trusted_foundations.h
+++ b/arch/arm/include/asm/trusted_foundations.h
@@ -30,6 +30,8 @@
#include <linux/printk.h>
#include <linux/bug.h>
#include <linux/of.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>

struct trusted_foundations_platform_data {
unsigned int version_major;
@@ -47,10 +49,13 @@ static inline void register_trusted_foundations(
struct trusted_foundations_platform_data *pd)
- * If we try to register TF, this means the system needs it to continue.
- * Its absence if thus a fatal error.
+ * If the system requires TF and we cannot provide it, continue booting
+ * but disable features that cannot be provided.
- panic("No support for Trusted Foundations, stopping...\n");
+ pr_err("No support for Trusted Foundations, continuing in degraded mode.\n");
+ pr_err("Secondary processors as well as CPU PM will be disabled.\n");
+ setup_max_cpus = 0;
+ cpu_idle_poll_ctrl(true);

static inline void of_register_trusted_foundations(void)

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/