[PATCH v1 2/3] i3c: master: svc: fix npcm845 FIFO empty issue

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

npcm845 HW issue:
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.
Workaround:
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 | 58 ++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 813839498b2b..22cb1f1c1fdc 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -102,6 +102,7 @@
 #define   SVC_I3C_MDATACTRL_TXTRIG_FIFO_NOT_FULL GENMASK(5, 4)
 #define   SVC_I3C_MDATACTRL_RXTRIG_FIFO_NOT_EMPTY 0
 #define   SVC_I3C_MDATACTRL_RXCOUNT(x) FIELD_GET(GENMASK(28, 24), (x))
+#define   SVC_I3C_MDATACTRL_TXCOUNT(x) FIELD_GET(GENMASK(20, 16), (x))
 #define   SVC_I3C_MDATACTRL_TXFULL BIT(30)
 #define   SVC_I3C_MDATACTRL_RXEMPTY BIT(31)
 
@@ -133,6 +134,16 @@
 #define SVC_I3C_EVENT_IBI	GENMASK(7, 0)
 #define SVC_I3C_EVENT_HOTJOIN	BIT(31)
 
+/*
+ * SVC_I3C_QUIRK_FIFO_EMPTY:
+ * 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.
+ * Workaround:
+ * Fill the FIFO in advance to prevent FIFO from becoming empty.
+ */
+#define SVC_I3C_QUIRK_FIFO_EMPTY	BIT(0)
+
 struct svc_i3c_cmd {
 	u8 addr;
 	bool rnw;
@@ -216,6 +227,7 @@ struct svc_i3c_master {
 	struct mutex lock;
 	u32 enabled_events;
 	u32 mctrl_config;
+	u32 quirks;
 };
 
 /**
@@ -891,6 +903,7 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
 	unsigned int dev_nb = 0, last_addr = 0;
 	u32 reg;
 	int ret, i;
+	u32 dyn_addr;
 
 	while (true) {
 		/* clean SVC_I3C_MINT_IBIWON w1c bits */
@@ -931,6 +944,15 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
 		if (SVC_I3C_MSTATUS_RXPEND(reg)) {
 			u8 data[6];
 
+			/*
+			 * SVC_I3C_QUIRK_FIFO_EMPTY fix:
+			 * The TX FIFO should be ready before the TX transmission is starting.
+			 */
+			dyn_addr = i3c_master_get_free_addr(&master->base, last_addr + 1);
+			if (dyn_addr < 0)
+				return dyn_addr;
+			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.
@@ -1009,21 +1031,20 @@ 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);
+	/*
+	 * Dynamic address is written to FIFO in advance for SVC_I3C_QUIRK_FIFO_EMPTY fix.
+	 * Flush FIFO in the failed case.
+	 */
+	if (ret)
+		svc_i3c_master_flush_fifo(master);
 	return ret;
 }
 
@@ -1210,7 +1231,6 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 	/* clean SVC_I3C_MINT_IBIWON w1c bits */
 	writel(SVC_I3C_MINT_IBIWON, master->regs + SVC_I3C_MSTATUS);
 
-
 	while (retry--) {
 		writel(SVC_I3C_MCTRL_REQUEST_START_ADDR |
 		       xfer_type |
@@ -1220,6 +1240,22 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
 		       SVC_I3C_MCTRL_RDTERM(*actual_len),
 		       master->regs + SVC_I3C_MCTRL);
 
+		if ((master->quirks & SVC_I3C_QUIRK_FIFO_EMPTY) && !rnw && xfer_len) {
+			int i, count, space;
+
+			reg = readl(master->regs + SVC_I3C_MDATACTRL);
+			space = SVC_I3C_FIFO_SIZE - SVC_I3C_MDATACTRL_TXCOUNT(reg);
+			count = xfer_len > space ? space : xfer_len;
+			for (i = 0; i < count; i++) {
+				if (i == xfer_len - 1)
+					writel(out[0], master->regs + SVC_I3C_MWDATABE);
+				else
+					writel(out[0], master->regs + SVC_I3C_MWDATAB);
+				out++;
+			}
+			xfer_len -= count;
+		}
+
 		ret = readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
 				 SVC_I3C_MSTATUS_MCTRLDONE(reg), 0, 1000);
 		if (ret)
@@ -1308,6 +1344,7 @@ 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;
 }
@@ -1877,6 +1914,9 @@ static int svc_i3c_master_probe(struct platform_device *pdev)
 
 	svc_i3c_master_reset(master);
 
+	if (device_is_compatible(master->dev, "nuvoton,npcm845-i3c"))
+		master->quirks = SVC_I3C_QUIRK_FIFO_EMPTY;
+
 	/* Register the master */
 	ret = i3c_master_register(&master->base, &pdev->dev,
 				  &svc_i3c_master_ops, false);
-- 
2.34.1


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