Re: [PATCH V2] ARM: mach-shmobile: Don't init CNTVOFF if PSCI is available

From: Oleksandr
Date: Fri May 10 2019 - 08:29:14 EST

On 06.05.19 18:37, Julien Grall wrote:
Hi Oleksandr,

Hi Julien

 arch/arm/mach-shmobile/setup-rcar-gen2.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-shmobile/setup-rcar-gen2.c b/arch/arm/mach-shmobile/setup-rcar-gen2.c
index eea60b2..bc8537b 100644
--- a/arch/arm/mach-shmobile/setup-rcar-gen2.c
+++ b/arch/arm/mach-shmobile/setup-rcar-gen2.c
@@ -17,7 +17,9 @@
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/of_platform.h>
+#include <xen/xen.h>
 #include <asm/mach/arch.h>
+#include <asm/psci.h>
 #include <asm/secure_cntvoff.h>
 #include "common.h"
 #include "rcar-gen2.h"
@@ -63,7 +65,16 @@ void __init rcar_gen2_timer_init(void)
ÂÂÂÂÂ void __iomem *base;
ÂÂÂÂÂ u32 freq;
 - secure_cntvoff_init();
+ÂÂÂ /*
+ÂÂÂÂ * If PSCI is available then most likely we are running on PSCI-enabled
+ÂÂÂÂ * U-Boot which, we assume, has already taken care of resetting CNTVOFF
+ÂÂÂÂ * before switching to non-secure mode and we don't need to.
+ÂÂÂÂ * Another check is to be sure that we are not running on top of Xen
+ÂÂÂÂ * hypervisor, as CNTVOFF is controlled by hypervisor itself and
+ÂÂÂÂ * shouldn't be touched by Dom0 in such case.

If you are running on top of Xen, then PSCI will be available. So is there any real value to check the presence of Xen as well?

I think, no. If the PSCI is a must to run Xen, then it is certainly an excessive check. I will drop it in V3.



Oleksandr Tyshchenko