Hi Kendall,

On Tue Sep 23, 2025 at 7:49 PM CEST, Kendall Willis wrote:

Hi Markus,

On 11:19-20250812, Markus Schneider-Pargmann wrote:

quoted

Add support for Partial-IO poweroff. In Partial-IO pins of a few
hardware units can generate system wakeups while DDR memory is not
powered resulting in a fresh boot of the system. These hardware units in
the SoC are always powered so that some logic can detect pin activity.

If the system supports Partial-IO as described in the fw capabilities, a
sys_off handler is added. This sys_off handler decides if the poweroff
is executed by entering normal poweroff or Partial-IO instead. The
decision is made by checking if wakeup is enabled on all devices that
may wake up the SoC from Partial-IO.

The possible wakeup devices are found by checking which devices
reference a "Partial-IO" system state in the list of wakeup-source
system states. Only devices that are actually enabled by the user will
be considered as an active wakeup source. If none of the wakeup sources
is enabled the system will do a normal poweroff. If at least one wakeup
source is enabled it will instead send a TI_SCI_MSG_PREPARE_SLEEP
message from the sys_off handler. Sending this message will result in an
immediate shutdown of the system. No execution is expected after this
point. The code will wait for 5s and do an emergency_restart afterwards
if Partial-IO wasn't entered at that point.

A short documentation about Partial-IO can be found in section 6.2.4.5
of the TRM at
  https://www.ti.com/lit/pdf/spruiv7

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
---
 drivers/firmware/ti_sci.c | 131 +++++++++++++++++++++++++++++++++++++++++++++-
 drivers/firmware/ti_sci.h |   5 ++
 2 files changed, 135 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
index c187fb714b3a4c658d0593c844716d4b160e4fa9..fb6f3d7f7413917cf9534ba65f0a9786d1183c71 100644
--- a/drivers/firmware/ti_sci.c
+++ b/drivers/firmware/ti_sci.c

@@ -3750,6 +3750,116 @@ static const struct dev_pm_ops ti_sci_pm_ops = {
 #endif
 };
 
+/*
+ * Enter Partial-IO, which disables everything including DDR with only a small
+ * logic being active for wakeup.
+ */
+static int ti_sci_enter_partial_io(struct ti_sci_info *info)
+{
+	struct ti_sci_msg_req_prepare_sleep *req;
+	struct ti_sci_xfer *xfer;
+	struct device *dev = info->dev;
+	int ret = 0;
+
+	xfer = ti_sci_get_one_xfer(info, TI_SCI_MSG_PREPARE_SLEEP,
+				   TI_SCI_FLAG_REQ_GENERIC_NORESPONSE,
+				   sizeof(*req), sizeof(struct ti_sci_msg_hdr));
+	if (IS_ERR(xfer)) {
+		ret = PTR_ERR(xfer);
+		dev_err(dev, "Message alloc failed(%d)\n", ret);
+		return ret;
+	}
+
+	req = (struct ti_sci_msg_req_prepare_sleep *)xfer->xfer_buf;
+	req->mode = TISCI_MSG_VALUE_SLEEP_MODE_PARTIAL_IO;
+	req->ctx_lo = 0;
+	req->ctx_hi = 0;
+	req->debug_flags = 0;
+
+	dev_info(dev, "Entering Partial-IO because a powered wakeup-enabled device was found.\n");
+

IMO this print should be in the ti_sci_sys_off_handler since that is
where the check is to find the wakeup-enabled device.

quoted

+	ret = ti_sci_do_xfer(info, xfer);
+	if (ret) {
+		dev_err(dev, "Mbox send fail %d\n", ret);
+		goto fail;
+	}
+
+fail:
+	ti_sci_put_one_xfer(&info->minfo, xfer);
+
+	return ret;
+}
+

Just something to think about: another way to implement this function
would be to change ti_sci_cmd_prepare_sleep to add a parameter of flags
for ti_sci_get_one_xfer in order to be able to choose if the
TI_SCI_FLAG_REQ_GENERIC_NORESPONSE or TI_SCI_FLAG_REQ_ACK_ON_PROCESSED
is used. This would make it so there's not duplicated code and
ti_sci_cmd_prepare_sleep could be used to enter partial IO.

Thanks for the suggestion, I just tried your approach and I personally
prefer the code as it is. I needed two additional ifs to switch to a
different rx_message_size and handle or not handle a response. In the
end there is not much common code left. Also the pattern is quite common
between many of the functions doing transfers.

Thanks for your review, I fixed the rest.

Best
Markus