[PATCH] drivers: psci: make PSCI 1.0 functions initialization version dependent

[Lorenzo Pieralisi]

The PSCI specifications [1] and the SMC calling convention mandate
that unimplemented functions ids must return NOT_SUPPORTED (0xffffffff)
if a function id is called but it is not implemented.

Consequently, PSCI 1.0 function ids that require the 1.0 PSCI_FEATURES
call to be initialized:

CPU_SUSPEND (psci_init_cpu_suspend())
SYSTEM_SUSPEND (psci_init_system_suspend())

call the PSCI_FEATURES function id independently of the detected
PSCI firmware version, since, if the PSCI_FEATURES function id is not
implemented, it must return NOT_SUPPORTED according to the PSCI
specifications, causing the initialization functions to fail as expected.

Some existing PSCI implementations (ie Qemu PSCI emulation), do not
comply with the SMC calling convention and fail if function ids that are
not implemented are called from the OS, causing boot failures.

To solve this issue, this patch adds code that checks the PSCI firmware
version before calling PSCI 1.0 initialization functions so that the
OS makes sure that it is calling 1.0 functions only if the firmware
version detected is 1.0 or greater, therefore avoiding PSCI calls
that are bound to fail and might cause system boot failures owing
to non-compliant PSCI firmware implementations.

[1] http://infocenter.arm.com/help/topic/com.arm.doc.den0022c/DEN0022C_Power_State_Coordination_Interface.pdf

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Kevin Hilman <khilman at kernel.org>
Cc: Sudeep Holla <sudeep.holla at arm.com>
Cc: Olof Johansson <olof at lixom.net>
Cc: Mark Rutland <mark.rutland at arm.com>
---
Arnd, Kevin, Olof,

this applies to current arm-soc drivers/psci branch, and solves the
issue Kevin detected through kernelci with Qemu emulation:

http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/380304.html

Tested on:

- Juno host
- AMD Seattle host
- kvmtool arm64 guest (on Juno arm64 defconfig host)
- Qemu x86 host (aarch64 emulation)

A run on kernelci and consequent tested-by tags would be much appreciated,
thanks for spotting this and for your help.

Thanks,
Lorenzo

 drivers/firmware/psci.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
index 492db42..d24f35d 100644
--- a/drivers/firmware/psci.c
+++ b/drivers/firmware/psci.c
@@ -347,9 +347,10 @@ static int __init psci_probe(void)
 
 	psci_init_migrate();
 
-	psci_init_cpu_suspend();
-
-	psci_init_system_suspend();
+	if (PSCI_VERSION_MAJOR(ver) >= 1) {
+		psci_init_cpu_suspend();
+		psci_init_system_suspend();
+	}
 
 	return 0;
 }
-- 
2.5.1