firmware: qcom: scm: Fix interrupted SCM calls

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 <andy.gross@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

3 files changed, 26 insertions, 7 deletions

diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
index ba60a8cb07d2..62522342e1e4 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
 
diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
index 4a0f5ead4fb5..1e2e5198db53 100644
--- a/drivers/firmware/qcom_scm-64.c
+++ b/drivers/firmware/qcom_scm-64.c
@@ -91,6 +91,7 @@ static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
         dma_addr_t args_phys = 0;
         void *args_virt = NULL;
         size_t alloc_len;
+        struct arm_smccc_quirk quirk = {.id = ARM_SMCCC_QUIRK_QCOM_A6};
 
         if (unlikely(arglen > N_REGISTER_ARGS)) {
                 alloc_len = N_EXT_QCOM_SCM_ARGS * sizeof(u64);
@@ -131,10 +132,16 @@ static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
                                          qcom_smccc_convention,
                                          ARM_SMCCC_OWNER_SIP, fn_id);
 
+                quirk.state.a6 = 0;
+
                 do {
-                        arm_smccc_smc(cmd, desc->arginfo, desc->args[0],
-                                      desc->args[1], desc->args[2], x5, 0, 0,
-                                      res);
+                        arm_smccc_smc_quirk(cmd, desc->arginfo, desc->args[0],
+                                      desc->args[1], desc->args[2], x5,
+                                      quirk.state.a6, 0, res, &quirk);
+
+                        if (res->a0 == QCOM_SCM_INTERRUPTED)
+                                cmd = res->a0;
+
                 } while (res->a0 == QCOM_SCM_INTERRUPTED);
 
                 mutex_unlock(&qcom_scm_lock);
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index c66f8ae94b5a..b67934164401 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -14,9 +14,6 @@
 #ifndef __LINUX_ARM_SMCCC_H
 #define __LINUX_ARM_SMCCC_H
 
-#include <linux/linkage.h>
-#include <linux/types.h>
-
 /*
  * This file provides common defines for ARM SMC Calling Convention as
  * specified in
@@ -60,6 +57,13 @@
 #define ARM_SMCCC_OWNER_TRUSTED_OS      50
 #define ARM_SMCCC_OWNER_TRUSTED_OS_END  63
 
+#define ARM_SMCCC_QUIRK_NONE            0
+#define ARM_SMCCC_QUIRK_QCOM_A6         1 /* Save/restore register a6 */
+
+#ifndef __ASSEMBLY__
+
+#include <linux/linkage.h>
+#include <linux/types.h>
 /**
  * struct arm_smccc_res - Result from SMC/HVC call
  * @a0-a3 result values from registers 0 to 3
@@ -125,4 +129,5 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 
 #define arm_smccc_hvc_quirk(...) __arm_smccc_hvc(__VA_ARGS__)
 
+#endif /*__ASSEMBLY__*/
 #endif /*__LINUX_ARM_SMCCC_H*/