[PATCH v1] serial: msm-geni: configure RX watermark register

[Gurumoorthy Santhakumar]

The SE_GENI_RX_WATERMARK_REG was not being programmed in the RX
setup paths. Set it to DEF_RX_WM (2) in qcom_geni_serial_start_rx(),
msm_geni_serial_setup_rx() and _debug_uart_init() to align with the
Linux kernel driver behaviour.

Without this, the RX FIFO watermark interrupt threshold is left at
its hardware reset value, which may differ from the expected value
and can cause RX data loss or missed watermark interrupts.

Link: https://lore.kernel.org/all/20200227132223.864425794@linuxfoundation.org/
Signed-off-by: Gurumoorthy Santhakumar <gurumoorthy.santhakumar at oss.qualcomm.com>
---
 drivers/serial/serial_msm_geni.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/serial/serial_msm_geni.c b/drivers/serial/serial_msm_geni.c
index 3dca581f68f..ae4015e0fdc 100644
--- a/drivers/serial/serial_msm_geni.c
+++ b/drivers/serial/serial_msm_geni.c
@@ -55,6 +55,7 @@
 #define SE_UART_RX_PARITY_CFG	0x2a8
 
 #define DEF_TX_WM	2
+#define DEF_RX_WM	2
 /* GENI_FORCE_DEFAULT_REG fields */
 
 #define UART_START_READ	0x1
@@ -345,6 +346,7 @@ static void qcom_geni_serial_start_rx(struct udevice *dev)
 
 	geni_se_setup_s_cmd(priv->base, UART_START_READ, 0);
 
+	writel(DEF_RX_WM, priv->base + SE_GENI_RX_WATERMARK_REG);
 	setbits_le32(priv->base + SE_GENI_S_IRQ_EN, S_RX_FIFO_WATERMARK_EN | S_RX_FIFO_LAST_EN);
 	setbits_le32(priv->base + SE_GENI_M_IRQ_EN, M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN);
 }
@@ -373,6 +375,7 @@ static void msm_geni_serial_setup_rx(struct udevice *dev)
 
 	geni_se_setup_s_cmd(priv->base, UART_START_READ, 0);
 
+	writel(DEF_RX_WM, priv->base + SE_GENI_RX_WATERMARK_REG);
 	setbits_le32(priv->base + SE_GENI_S_IRQ_EN, S_RX_FIFO_WATERMARK_EN | S_RX_FIFO_LAST_EN);
 	setbits_le32(priv->base + SE_GENI_M_IRQ_EN, M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN);
 }
@@ -616,6 +619,7 @@ static inline void _debug_uart_init(void)
 	phys_addr_t base = CONFIG_VAL(DEBUG_UART_BASE);
 
 	geni_serial_init(&init_dev);
+	writel(DEF_RX_WM, base + SE_GENI_RX_WATERMARK_REG);
 	geni_serial_baud(base, CLK_DIV, CONFIG_BAUDRATE);
 	qcom_geni_serial_start_tx(base);
 }
-- 
2.34.1