[PATCH v4 2/2] firmware: arm_scmi: Augment SMC/HVC to allow optional parameters

[Nikunj Kela <quic_nkela@xxxxxxxxxxx>]

This patch add support for passing shmem channel address as parameters
in smc/hvc call. The address is split into 4KB-page and offset.
This patch is useful when multiple scmi instances are using same smc-id
and firmware needs to distinguish among the instances.

Signed-off-by: Nikunj Kela <quic_nkela@xxxxxxxxxxx>
---
 drivers/firmware/arm_scmi/driver.c |  1 +
 drivers/firmware/arm_scmi/smc.c    | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index e7d97b59963b..b5957cc12fee 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -2914,6 +2914,7 @@ static const struct of_device_id scmi_of_match[] = {
 #endif
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
 	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
+	{ .compatible = "arm,scmi-smc-param", .data = &scmi_smc_desc},
 #endif
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
 	{ .compatible = "arm,scmi-virtio", .data = &scmi_virtio_desc},
diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c
index 93272e4bbd12..71e080b70df5 100644
--- a/drivers/firmware/arm_scmi/smc.c
+++ b/drivers/firmware/arm_scmi/smc.c
@@ -20,6 +20,11 @@
 
 #include "common.h"
 
+#define SHMEM_SHIFT 12
+#define SHMEM_SIZE (_AC(1, UL) << SHMEM_SHIFT)
+#define SHMEM_PAGE(x) ((unsigned long)((x) >> SHMEM_SHIFT))
+#define SHMEM_OFFSET(x) ((x) & (SHMEM_SIZE - 1))
+
 /**
  * struct scmi_smc - Structure representing a SCMI smc transport
  *
@@ -30,6 +35,7 @@
  * @inflight: Atomic flag to protect access to Tx/Rx shared memory area.
  *	      Used when operating in atomic mode.
  * @func_id: smc/hvc call function id
+ * @param: physical address of the shmem channel
  */
 
 struct scmi_smc {
@@ -40,6 +46,7 @@ struct scmi_smc {
 #define INFLIGHT_NONE	MSG_TOKEN_MAX
 	atomic_t inflight;
 	u32 func_id;
+	phys_addr_t param;
 };
 
 static irqreturn_t smc_msg_done_isr(int irq, void *data)
@@ -137,6 +144,8 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
 	if (ret < 0)
 		return ret;
 
+	if (of_device_is_compatible(dev->of_node, "arm,scmi-smc-param"))
+		scmi_info->param = res.start;
 	/*
 	 * If there is an interrupt named "a2p", then the service and
 	 * completion of a message is signaled by an interrupt rather than by
@@ -179,6 +188,8 @@ static int smc_send_message(struct scmi_chan_info *cinfo,
 {
 	struct scmi_smc *scmi_info = cinfo->transport_info;
 	struct arm_smccc_res res;
+	unsigned long page = SHMEM_PAGE(scmi_info->param);
+	unsigned long offset = SHMEM_OFFSET(scmi_info->param);
 
 	/*
 	 * Channel will be released only once response has been
@@ -188,7 +199,8 @@ static int smc_send_message(struct scmi_chan_info *cinfo,
 
 	shmem_tx_prepare(scmi_info->shmem, xfer, cinfo);
 
-	arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res);
+	arm_smccc_1_1_invoke(scmi_info->func_id, page, offset, 0, 0, 0, 0, 0,
+			     &res);
 
 	/* Only SMCCC_RET_NOT_SUPPORTED is valid error code */
 	if (res.a0) {
-- 
2.17.1