[PATCH v2 1/1] serial: npcm: Add support for Nuvoton NPCM SoCs

[Stanley Chu]

Add Nuvoton BMC NPCM7xx/NPCM8xx uart driver

Signed-off-by: Stanley Chu <yschu at nuvoton.com>
---
Changes in v2:
  Drop unnecessary outer brackets.
  Return -EAGAIN if not ready for tx/rx.
  Add comments.
---
 drivers/serial/Kconfig       |   9 +++
 drivers/serial/Makefile      |   1 +
 drivers/serial/serial_npcm.c | 150 +++++++++++++++++++++++++++++++++++
 3 files changed, 160 insertions(+)
 create mode 100644 drivers/serial/serial_npcm.c

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 6c8fdda9a0..e67a76a424 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -920,6 +920,15 @@ config MPC8XX_CONS
 	depends on MPC8xx
 	default y
 
+config NPCM_SERIAL
+	bool "UART driver for Nuvoton NPCM BMC"
+	depends on DM_SERIAL
+	help
+	  Select this to enable UART support for Nuvoton BMCs
+	  (NPCM7xx and NPCM8xx).
+	  The driver enables the onboard serial port with 8-N-1
+	  configuration.
+
 config XEN_SERIAL
 	bool "XEN serial support"
 	depends on XEN
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 8168af640f..866495e416 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -73,6 +73,7 @@ obj-$(CONFIG_OWL_SERIAL) += serial_owl.o
 obj-$(CONFIG_OMAP_SERIAL) += serial_omap.o
 obj-$(CONFIG_MTK_SERIAL) += serial_mtk.o
 obj-$(CONFIG_MT7620_SERIAL) += serial_mt7620.o
+obj-$(CONFIG_NPCM_SERIAL) += serial_npcm.o
 obj-$(CONFIG_SIFIVE_SERIAL) += serial_sifive.o
 obj-$(CONFIG_XEN_SERIAL) += serial_xen.o
 
diff --git a/drivers/serial/serial_npcm.c b/drivers/serial/serial_npcm.c
new file mode 100644
index 0000000000..0c6f0410cf
--- /dev/null
+++ b/drivers/serial/serial_npcm.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2021 Nuvoton Technology Corp.
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <serial.h>
+
+struct npcm_uart {
+	union {
+		u32	rbr;	/* Receive Buffer Register */
+		u32	thr;	/* Transmit Holding Register */
+		u32	dll;	/* Divisor Latch (Low Byte) Register */
+	};
+	union {
+		u32	ier;	/* Interrupt Enable Register */
+		u32	dlm;	/* Divisor Latch (Low Byte) Register */
+	};
+	union {
+		u32	iir;	/* Interrupt Identification Register */
+		u32	fcr;	/* FIFO Control Register */
+	};
+	u32	lcr;		/* Line Control Register */
+	u32	mcr;		/* Modem Control Register */
+	u32	lsr;		/* Line Status Control Register */
+	u32	msr;		/* Modem Status Register */
+	u32	tor;		/* Timeout Register */
+};
+
+#define	LCR_WLS_8BITS	3	/* 8-bit word length select */
+#define	FCR_TFR		BIT(2)	/* TxFIFO reset */
+#define	FCR_RFR		BIT(1)	/* RxFIFO reset */
+#define	FCR_FME		BIT(0)	/* FIFO mode enable */
+#define	LSR_THRE	BIT(5)	/* Status of TxFIFO empty */
+#define	LSR_RFDR	BIT(0)	/* Status of RxFIFO data ready */
+#define	LCR_DLAB	BIT(7)	/* Divisor latch access bit */
+
+struct npcm_serial_plat {
+	struct npcm_uart *reg;
+	u32 uart_clk;		/* frequency of uart clock source */
+};
+
+static int npcm_serial_pending(struct udevice *dev, bool input)
+{
+	struct npcm_serial_plat *plat = dev_get_plat(dev);
+	struct npcm_uart *uart = plat->reg;
+
+	if (input)
+		return readb(&uart->lsr) & LSR_RFDR ? 1 : 0;
+	else
+		return readb(&uart->lsr) & LSR_THRE ? 0 : 1;
+}
+
+static int npcm_serial_putc(struct udevice *dev, const char ch)
+{
+	struct npcm_serial_plat *plat = dev_get_plat(dev);
+	struct npcm_uart *uart = plat->reg;
+
+	if (!(readb(&uart->lsr) & LSR_THRE))
+		return -EAGAIN;
+
+	writeb(ch, &uart->thr);
+
+	return 0;
+}
+
+static int npcm_serial_getc(struct udevice *dev)
+{
+	struct npcm_serial_plat *plat = dev_get_plat(dev);
+	struct npcm_uart *uart = plat->reg;
+
+	if (!(readb(&uart->lsr) & LSR_RFDR))
+		return -EAGAIN;
+
+	return readb(&uart->rbr);
+}
+
+static int npcm_serial_setbrg(struct udevice *dev, int baudrate)
+{
+	struct npcm_serial_plat *plat = dev_get_plat(dev);
+	struct npcm_uart *uart = plat->reg;
+	u16 divisor;
+
+	/* BaudOut = UART Clock / (16 * [Divisor + 2]) */
+	divisor = DIV_ROUND_CLOSEST(plat->uart_clk, 16 * baudrate + 2) - 2;
+
+	setbits_8(&uart->lcr, LCR_DLAB);
+	writeb(divisor & 0xff, &uart->dll);
+	writeb(divisor >> 8, &uart->dlm);
+	clrbits_8(&uart->lcr, LCR_DLAB);
+
+	return 0;
+}
+
+static int npcm_serial_probe(struct udevice *dev)
+{
+	struct npcm_serial_plat *plat = dev_get_plat(dev);
+	struct npcm_uart *uart = plat->reg;
+	struct clk clk;
+	u32 freq;
+	int ret;
+
+	plat->reg = dev_read_addr_ptr(dev);
+	freq = dev_read_u32_default(dev, "clock-frequency", 0);
+
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret < 0)
+		return ret;
+
+	ret = clk_set_rate(&clk, freq);
+	if (ret < 0)
+		return ret;
+	plat->uart_clk = ret;
+
+	/* Disable all interrupt */
+	writeb(0, &uart->ier);
+
+	/* Set 8 bit, 1 stop, no parity */
+	writeb(LCR_WLS_8BITS, &uart->lcr);
+
+	/* Reset RX/TX FIFO */
+	writeb(FCR_FME | FCR_RFR | FCR_TFR, &uart->fcr);
+
+	return 0;
+}
+
+static const struct dm_serial_ops npcm_serial_ops = {
+	.getc = npcm_serial_getc,
+	.setbrg = npcm_serial_setbrg,
+	.putc = npcm_serial_putc,
+	.pending = npcm_serial_pending,
+};
+
+static const struct udevice_id npcm_serial_ids[] = {
+	{ .compatible = "nuvoton,npcm750-uart" },
+	{ .compatible = "nuvoton,npcm845-uart" },
+	{ }
+};
+
+U_BOOT_DRIVER(serial_npcm) = {
+	.name	= "serial_npcm",
+	.id	= UCLASS_SERIAL,
+	.of_match = npcm_serial_ids,
+	.plat_auto  = sizeof(struct npcm_serial_plat),
+	.probe = npcm_serial_probe,
+	.ops	= &npcm_serial_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};
-- 
2.17.1