[PATCH v5 2/2] firmware: arm_scmi: Add qcom smc/hvc transport support

[Nikunj Kela]

This change adds the support for SCMI message exchange on Qualcomm
virtual platforms.

The hypervisor associates an object-id also known as capability-id
with each smc/hvc doorbell object. The capability-id is used to
identify the doorbell from the VM's capability namespace, similar
to a file-descriptor.

The hypervisor, in addition to the function-id, expects the capability-id
to be passed in x1 register when SMC/HVC call is invoked.

The capability-id is allocated by the hypervisor on bootup and is stored in
the shmem region by the firmware before starting Linux.

Signed-off-by: Nikunj Kela <quic_nkela@xxxxxxxxxxx>
---
 drivers/firmware/arm_scmi/driver.c |  1 +
 drivers/firmware/arm_scmi/smc.c    | 33 ++++++++++++++++++++++++++++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 87383c05424b..09371f40d61f 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -2915,6 +2915,7 @@ static const struct of_device_id scmi_of_match[] = {
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
 	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
 	{ .compatible = "arm,scmi-smc-param", .data = &scmi_smc_desc},
+	{ .compatible = "qcom,scmi-smc", .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 c193516a254d..3d594d65ab14 100644
--- a/drivers/firmware/arm_scmi/smc.c
+++ b/drivers/firmware/arm_scmi/smc.c
@@ -50,6 +50,8 @@
  * @func_id: smc/hvc call function id
  * @param_page: 4K page number of the shmem channel
  * @param_offset: Offset within the 4K page of the shmem channel
+ * @cap_id: smc/hvc doorbell's capability id to be used on Qualcomm virtual
+ *	    platforms
  */
 
 struct scmi_smc {
@@ -63,6 +65,7 @@ struct scmi_smc {
 	u32 func_id;
 	u32 param_page;
 	u32 param_offset;
+	s64 cap_id;
 };
 
 static irqreturn_t smc_msg_done_isr(int irq, void *data)
@@ -128,6 +131,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
 	resource_size_t size;
 	struct resource res;
 	struct device_node *np;
+	s64 cap_id = -EINVAL;
 	u32 func_id;
 	int ret;
 
@@ -162,6 +166,25 @@ 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, "qcom,scmi-smc")) {
+		/* The capability-id is kept in last 8 bytes of shmem.
+		 *     +-------+
+		 *     |       |
+		 *     | shmem |
+		 *     |       |
+		 *     |       |
+		 *     +-------+ <-- (size - 8)
+		 *     | capId |
+		 *     +-------+ <-- size
+		 */
+
+#ifdef CONFIG_64BIT
+		cap_id = ioread64((void *)scmi_info->shmem + size - 8);
+#else
+		cap_id = ioread32((void *)scmi_info->shmem + size - 8);
+#endif
+	}
+
 	if (of_device_is_compatible(dev->of_node, "arm,scmi-smc-param")) {
 		scmi_info->param_page = SHMEM_PAGE(res.start);
 		scmi_info->param_offset = SHMEM_OFFSET(res.start);
@@ -184,6 +207,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
 	}
 
 	scmi_info->func_id = func_id;
+	scmi_info->cap_id = cap_id;
 	scmi_info->cinfo = cinfo;
 	smc_channel_lock_init(scmi_info);
 	cinfo->transport_info = scmi_info;
@@ -213,6 +237,7 @@ static int smc_send_message(struct scmi_chan_info *cinfo,
 	struct arm_smccc_res res;
 	unsigned long page = scmi_info->param_page;
 	unsigned long offset = scmi_info->param_offset;
+	long cap_id = (long)scmi_info->cap_id;
 
 	/*
 	 * Channel will be released only once response has been
@@ -222,8 +247,12 @@ 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, page, offset, 0, 0, 0, 0, 0,
-			     &res);
+	if (cap_id >= 0)
+		arm_smccc_1_1_invoke(scmi_info->func_id, cap_id, 0, 0, 0, 0, 0,
+				     0, &res);
+	else
+		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