[PATCH v4 3/5] i3c: master: svc: Fix npcm845 FIFO empty issue

[Stanley Chu <stanley.chuys@gmail.com>]

From: Stanley Chu <yschu@nuvoton.com>

I3C HW stalls the write transfer if the transmit FIFO becomes empty,
when new data is written to FIFO, I3C HW resumes the transfer but the
first transmitted data bit may have the wrong value.
Fill the FIFO in advance to prevent FIFO from becoming empty.

Signed-off-by: Stanley Chu <yschu@nuvoton.com>
---
 drivers/i3c/master/svc-i3c-master.c | 44 ++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 8834f87a4767..07506ae0f914 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -942,7 +942,7 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
 					u8 *addrs, unsigned int *count)
 {
 	u64 prov_id[SVC_I3C_MAX_DEVS] = {}, nacking_prov_id = 0;
-	unsigned int dev_nb = 0, last_addr = 0;
+	unsigned int dev_nb = 0, last_addr = 0, dyn_addr;
 	u32 reg;
 	int ret, i;
 
@@ -985,6 +985,17 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
 		if (SVC_I3C_MSTATUS_RXPEND(reg)) {
 			u8 data[6];
 
+			/*
+			 * One slave sends its ID to request for address assignment,
+			 * pre-filling the dynamic address can reduce SCL clock stalls
+			 * and also fix the SVC_I3C_QUIRK_FIFO_EMPTY quirk.
+			 */
+			dyn_addr = i3c_master_get_free_addr(&master->base, last_addr + 1);
+			if (dyn_addr < 0)
+				return -ENOSPC;
+
+			writel(dyn_addr, master->regs + SVC_I3C_MWDATAB);
+
 			/*
 			 * We only care about the 48-bit provisioned ID yet to
 			 * be sure a device does not nack an address twice.
@@ -1063,21 +1074,16 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
 		if (ret)
 			break;
 
-		/* Give the slave device a suitable dynamic address */
-		ret = i3c_master_get_free_addr(&master->base, last_addr + 1);
-		if (ret < 0)
-			break;
-
-		addrs[dev_nb] = ret;
+		addrs[dev_nb] = dyn_addr;
 		dev_dbg(master->dev, "DAA: device %d assigned to 0x%02x\n",
 			dev_nb, addrs[dev_nb]);
-
-		writel(addrs[dev_nb], master->regs + SVC_I3C_MWDATAB);
 		last_addr = addrs[dev_nb++];
 	}
 
 	/* Need manual issue STOP except for Complete condition */
 	svc_i3c_master_emit_stop(master);
+	svc_i3c_master_flush_fifo(master);
+
 	return ret;
 }
 
@@ -1225,8 +1231,8 @@ static int svc_i3c_master_read(struct svc_i3c_master *master,
 	return offset;
 }
 
-static int svc_i3c_master_write(struct svc_i3c_master *master,
-				const u8 *out, unsigned int len)
+static int svc_i3c_master_write(struct svc_i3c_master *master, const u8 *out,
+				unsigned int len, bool last)
 {
 	int offset = 0, ret;
 	u32 mdctrl;
@@ -1243,7 +1249,7 @@ static int svc_i3c_master_write(struct svc_i3c_master *master,
 		 * The last byte to be sent over the bus must either have the
 		 * "end" bit set or be written in MWDATABE.
 		 */
-		if (likely(offset < (len - 1)))
+		if (likely(offset < (len - 1)) || !last)
 			writel(out[offset++], master->regs + SVC_I3C_MWDATAB);
 		else
 			writel(out[offset++], master->regs + SVC_I3C_MWDATABE);
@@ -1274,6 +1280,17 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 		       SVC_I3C_MCTRL_RDTERM(*actual_len),
 		       master->regs + SVC_I3C_MCTRL);
 
+		if (svc_has_quirk(master, SVC_I3C_QUIRK_FIFO_EMPTY) && !rnw && xfer_len) {
+			u32 len = min_t(u32, xfer_len, SVC_I3C_FIFO_SIZE);
+
+			ret = svc_i3c_master_write(master, out, len,
+						   xfer_len <= SVC_I3C_FIFO_SIZE);
+			if (ret < 0)
+				goto emit_stop;
+			xfer_len -= len;
+			out += len;
+		}
+
 		ret = readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
 				 SVC_I3C_MSTATUS_MCTRLDONE(reg), 0, 1000);
 		if (ret)
@@ -1335,7 +1352,7 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 	if (rnw)
 		ret = svc_i3c_master_read(master, in, xfer_len);
 	else
-		ret = svc_i3c_master_write(master, out, xfer_len);
+		ret = svc_i3c_master_write(master, out, xfer_len, true);
 	if (ret < 0)
 		goto emit_stop;
 
@@ -1362,6 +1379,7 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 emit_stop:
 	svc_i3c_master_emit_stop(master);
 	svc_i3c_master_clear_merrwarn(master);
+	svc_i3c_master_flush_fifo(master);
 
 	return ret;
 }
-- 
2.34.1