i3c: master: svc: fix ibi may not return mandatory data byte

MSTATUS[RXPEND] is only updated after the data transfer cycle started. This
creates an issue when the I3C clock is slow, and the CPU is running fast
enough that MSTATUS[RXPEND] may not be updated when the code reaches
checking point. As a result, mandatory data can be missed.

Add a wait for MSTATUS[COMPLETE] to ensure that all mandatory data is
already in FIFO. It also works without mandatory data.

Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver")
Cc: <[e-mail]>
Reviewed-by: Miquel Raynal <[e-mail]>
Signed-off-by: Frank Li <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/i3c/master/svc-i3c-master.c

···
 	struct i3c_ibi_slot *slot;
 	unsigned int count;
 	u32 mdatactrl;
+	int ret, val;
 	u8 *buf;
 
 	slot = i3c_generic_ibi_get_free_slot(data->ibi_pool);
···
 
 	slot->len = 0;
 	buf = slot->data;
+
+	ret = readl_relaxed_poll_timeout(master->regs + SVC_I3C_MSTATUS, val,
+						SVC_I3C_MSTATUS_COMPLETE(val), 0, 1000);
+	if (ret) {
+		dev_err(master->dev, "Timeout when polling for COMPLETE\n");
+		return ret;
+	}
 
 	while (SVC_I3C_MSTATUS_RXPEND(readl(master->regs + SVC_I3C_MSTATUS))  &&
 	       slot->len < SVC_I3C_FIFO_SIZE) {