This patch adds a Qualcomm specific quirk to the arm_smccc_smc call.

On Qualcomm ARM64 platforms, the SMC call can return before it has
completed.  If this occurs, the call can be restarted, but it requires
using the returned session ID value from the interrupted SMC call.

The quirk stores off the session ID from the interrupted call in the
quirk structure so that it can be used by the caller.

This patch folds in a fix given by Sricharan R:
https://lkml.org/lkml/2016/9/28/272

Signed-off-by: Andy Gross <redacted>
Reviewed-by: Will Deacon <redacted>
---
 arch/arm64/kernel/smccc-call.S |  9 ++++++++-
 drivers/firmware/qcom_scm-64.c | 13 ++++++++++---
 include/linux/arm-smccc.h      | 11 ++++++++---
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
index 6290696..72ecdca 100644
--- a/arch/arm64/kernel/smccc-call.S
+++ b/arch/arm64/kernel/smccc-call.S

@@ -12,6 +12,7 @@
  *
  */
 #include <linux/linkage.h>
+#include <linux/arm-smccc.h>
 #include <asm/asm-offsets.h>

        .macro SMCCC instr

@@ -20,7 +21,13 @@
        ldr     x4, [sp]
        stp     x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
        stp     x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
-       ret
+       ldr     x4, [sp, #8]
+       cbz     x4, 1f /* no quirk structure */
+       ldr     x9, [x4, #ARM_SMCCC_QUIRK_ID_OFFS]
+       cmp     x9, #ARM_SMCCC_QUIRK_QCOM_A6
+       b.ne    1f
+       str     x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS]
+1:     ret
        .cfi_endproc
        .endm