[PATCH v4 1/4] firmware: arm_scmi: Add polling support for completion in smc

[Nikunj Kela]

Currently, the return from the smc call assumes the completion of
the scmi request. However this may not be true in virtual platforms
that are using hvc doorbell.

This change adds a Kconfig to enable the polling for the request
completion.

Signed-off-by: Nikunj Kela <quic_nkela at quicinc.com>
---
 drivers/firmware/arm_scmi/Kconfig | 14 ++++++++++++++
 drivers/firmware/arm_scmi/smc.c   | 15 ++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig
index ea0f5083ac47..771d60f8319f 100644
--- a/drivers/firmware/arm_scmi/Kconfig
+++ b/drivers/firmware/arm_scmi/Kconfig
@@ -125,6 +125,20 @@ config ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE
 	  in atomic context too, at the price of using a number of busy-waiting
 	  primitives all over instead. If unsure say N.
 
+config ARM_SCMI_TRANSPORT_SMC_POLL_COMPLETION
+	bool "Enable polling support for SCMI SMC transport"
+	depends on ARM_SCMI_TRANSPORT_SMC
+	help
+	  Enable completion polling support for SCMI SMC based transport.
+
+	  If you want the SCMI SMC based transport to poll for the completion,
+	  answer Y.
+	  Enabling completion polling might be desired in the absence of the a2p
+	  irq when the return from smc/hvc call doesn't indicate the completion
+	  of the SCMI requests. This might be useful for instances used in
+	  virtual platforms.
+	  If unsure say N.
+
 config ARM_SCMI_TRANSPORT_VIRTIO
 	bool "SCMI transport based on VirtIO"
 	depends on VIRTIO=y || VIRTIO=ARM_SCMI_PROTOCOL
diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c
index c193516a254d..0a0b7e401159 100644
--- a/drivers/firmware/arm_scmi/smc.c
+++ b/drivers/firmware/arm_scmi/smc.c
@@ -250,6 +250,16 @@ static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret,
 	smc_channel_lock_release(scmi_info);
 }
 
+#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_POLL_COMPLETION
+static bool
+smc_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
+{
+	struct scmi_smc *scmi_info = cinfo->transport_info;
+
+	return shmem_poll_done(scmi_info->shmem, xfer);
+}
+#endif
+
 static const struct scmi_transport_ops scmi_smc_ops = {
 	.chan_available = smc_chan_available,
 	.chan_setup = smc_chan_setup,
@@ -257,6 +267,9 @@ static const struct scmi_transport_ops scmi_smc_ops = {
 	.send_message = smc_send_message,
 	.mark_txdone = smc_mark_txdone,
 	.fetch_response = smc_fetch_response,
+#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_POLL_COMPLETION
+	.poll_done = smc_poll_done,
+#endif
 };
 
 const struct scmi_desc scmi_smc_desc = {
@@ -272,6 +285,6 @@ const struct scmi_desc scmi_smc_desc = {
 	 * for the issued command will be immmediately ready to be fetched
 	 * from the shared memory area.
 	 */
-	.sync_cmds_completed_on_ret = true,
+	.sync_cmds_completed_on_ret = !IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_POLL_COMPLETION),
 	.atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE),
 };
-- 
2.17.1