[PATCH v4 16/16] firmware: arm_scmi: Add polling mode to virtio transport
From: Cristian Marussi <cristian.marussi@arm.com>
Date: 2021-06-11 17:01:43
Also in:
lkml
Subsystem:
system control & power/management interface (scpi/scmi) message protocol drivers, the rest · Maintainers:
Sudeep Holla, Linus Torvalds
Enable polling mode support to virtio transport. Upon reception of a synchronous command response for a transfer that has the hdr.poll_completion flag set, virtio transport now simply completes the same completion which .poll_done() is spinning on. Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> --- Note that as of now in order to test this you have to forcibly enable hdr.poll_completion in the core and increase SCMI_MAX_POLL_TO_NS. These workarounds won't be needed anymore once addressed by a distinct series currently under review. --- drivers/firmware/arm_scmi/virtio.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c
index 4412bc590ca7..f77c7f288d4c 100644
--- a/drivers/firmware/arm_scmi/virtio.c
+++ b/drivers/firmware/arm_scmi/virtio.c@@ -158,12 +158,12 @@ static void scmi_process_vqueue_input(struct scmi_vio_channel *vioch, /* Drop processed virtio message anyway */ scmi_finalize_message(vioch, msg); + /* Deliver DRESP, NOTIF and non-polled RESP */ if (vioch->is_rx || !xfer->hdr.poll_completion) scmi_rx_callback(vioch->cinfo, msg_hdr); else - dev_warn(vioch->cinfo->dev, - "Polling mode NOT supported. Dropped hdr:0X%X\n", - msg_hdr); + /* poll_done() is busy-waiting on this */ + complete(&xfer->done); scmi_transfer_release(vioch->cinfo, xfer); }
@@ -414,10 +414,16 @@ static void dummy_clear_channel(struct scmi_chan_info *cinfo) { } -static bool dummy_poll_done(struct scmi_chan_info *cinfo, - struct scmi_xfer *xfer) +static bool virtio_poll_done(struct scmi_chan_info *cinfo, + struct scmi_xfer *xfer) { - return false; + /* + * In polling mode SCMI core does not use xfer->done completion, + * so we can busy-wait on this same completion without adding + * a new flag: this is completed properly upon msg reception in + * scmi_process_vqueue_input(). + */ + return try_wait_for_completion(&xfer->done); } static const struct scmi_transport_ops scmi_virtio_ops = {
@@ -430,7 +436,7 @@ static const struct scmi_transport_ops scmi_virtio_ops = { .fetch_response = virtio_fetch_response, .fetch_notification = virtio_fetch_notification, .clear_channel = dummy_clear_channel, - .poll_done = dummy_poll_done, + .poll_done = virtio_poll_done, }; static int scmi_vio_probe(struct virtio_device *vdev)
--
2.17.1
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