[PATCH] ARM: kernel: Fix interrupted SMC calls

From: Manivannan Sadhasivam
Date: Mon Jan 18 2021 - 10:54:09 EST

On Qualcomm ARM32 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 ARM32 SMCC code already has the provision to add platform specific
quirks for things like this. So let's make use of it and add the
Qualcomm specific quirk (ARM_SMCCC_QUIRK_QCOM_A6) used by the QCOM_SCM

This change is similar to the below one added for ARM64 a while ago:
commit 82bcd087029f ("firmware: qcom: scm: Fix interrupted SCM calls")

Without this change, the Qualcomm ARM32 platforms like SDX55 will return
-EINVAL for SMC calls used for modem firmware loading and validation.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
arch/arm/kernel/asm-offsets.c | 3 +++
arch/arm/kernel/smccc-call.S | 12 +++++++++++-
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index a1570c8bab25..2e2fa6fc2d4f 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -23,6 +23,7 @@
#include <asm/vdso_datapage.h>
#include <asm/hardware/cache-l2x0.h>
#include <linux/kbuild.h>
+#include <linux/arm-smccc.h>
#include "signal.h"

@@ -147,6 +148,8 @@ int main(void)
DEFINE(SLEEP_SAVE_SP_PHYS, offsetof(struct sleep_save_sp, save_ptr_stash_phys));
DEFINE(SLEEP_SAVE_SP_VIRT, offsetof(struct sleep_save_sp, save_ptr_stash));
+ DEFINE(ARM_SMCCC_QUIRK_ID_OFFS, offsetof(struct arm_smccc_quirk, id));
+ DEFINE(ARM_SMCCC_QUIRK_STATE_OFFS, offsetof(struct arm_smccc_quirk, state));
diff --git a/arch/arm/kernel/smccc-call.S b/arch/arm/kernel/smccc-call.S
index 00664c78faca..e1ab00b8244b 100644
--- a/arch/arm/kernel/smccc-call.S
+++ b/arch/arm/kernel/smccc-call.S
@@ -3,7 +3,9 @@
* Copyright (c) 2015, Linaro Limited
#include <linux/linkage.h>
+#include <linux/arm-smccc.h>

+#include <asm/asm-offsets.h>
#include <asm/opcodes-sec.h>
#include <asm/opcodes-virt.h>
#include <asm/unwind.h>
@@ -27,10 +29,18 @@ UNWIND( .fnstart)
UNWIND( .save {r4-r7})
ldm r12, {r4-r7}
+ mov r9, r6 // Copy r6 before popping from stack
pop {r4-r7}
ldr r12, [sp, #(4 * 4)]
stm r12, {r0-r3}
- bx lr
+ ldr r10, [sp, #20]
+ cmp r10, #0
+ beq 1f // No quirk structure
+ ldr r11, [r10, #ARM_SMCCC_QUIRK_ID_OFFS]
+ bne 1f // No quirk present
+ str r9, [r10, #ARM_SMCCC_QUIRK_STATE_OFFS]
+1: bx lr
UNWIND( .fnend)