serial: MediaTek: add high-speed uart driver for MediaTek SoCs
Many SoCs from MediaTek have a high-speed uart. This UART is compatible
with the ns16550 in legacy mode. It has extra registers for high-speed
mode which can reach a maximum baudrate at 921600.
However this UART will no longer be compatible if it's in high-speed mode.
Some BootROM of MediaTek's SoCs will change the UART into high-speed mode
and the U-Boot must use this driver to initialize the UART.
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
Tested-by: Ryder Lee <ryder.lee@mediatek.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/serial_mtk.c b/drivers/serial/serial_mtk.c
new file mode 100644
index 0000000..bce1be8
--- /dev/null
+++ b/drivers/serial/serial_mtk.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MediaTek High-speed UART driver
+ *
+ * Copyright (C) 2018 MediaTek Inc.
+ * Author: Weijie Gao <weijie.gao@mediatek.com>
+ */
+
+#include <clk.h>
+#include <common.h>
+#include <div64.h>
+#include <dm.h>
+#include <errno.h>
+#include <serial.h>
+#include <watchdog.h>
+#include <asm/io.h>
+#include <asm/types.h>
+
+struct mtk_serial_regs {
+ u32 rbr;
+ u32 ier;
+ u32 fcr;
+ u32 lcr;
+ u32 mcr;
+ u32 lsr;
+ u32 msr;
+ u32 spr;
+ u32 mdr1;
+ u32 highspeed;
+ u32 sample_count;
+ u32 sample_point;
+ u32 fracdiv_l;
+ u32 fracdiv_m;
+ u32 escape_en;
+ u32 guard;
+ u32 rx_sel;
+};
+
+#define thr rbr
+#define iir fcr
+#define dll rbr
+#define dlm ier
+
+#define UART_LCR_WLS_8 0x03 /* 8 bit character length */
+#define UART_LCR_DLAB 0x80 /* Divisor latch access bit */
+
+#define UART_LSR_DR 0x01 /* Data ready */
+#define UART_LSR_THRE 0x20 /* Xmit holding register empty */
+
+/* the data is correct if the real baud is within 3%. */
+#define BAUD_ALLOW_MAX(baud) ((baud) + (baud) * 3 / 100)
+#define BAUD_ALLOW_MIX(baud) ((baud) - (baud) * 3 / 100)
+
+struct mtk_serial_priv {
+ struct mtk_serial_regs __iomem *regs;
+ u32 clock;
+};
+
+static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud)
+{
+ bool support_clk12m_baud115200;
+ u32 quot, samplecount, realbaud;
+
+ if ((baud <= 115200) && (priv->clock == 12000000))
+ support_clk12m_baud115200 = true;
+ else
+ support_clk12m_baud115200 = false;
+
+ if (baud <= 115200) {
+ writel(0, &priv->regs->highspeed);
+ quot = DIV_ROUND_CLOSEST(priv->clock, 16 * baud);
+
+ if (support_clk12m_baud115200) {
+ writel(3, &priv->regs->highspeed);
+ quot = DIV_ROUND_CLOSEST(priv->clock, 256 * baud);
+ if (quot == 0)
+ quot = 1;
+
+ samplecount = DIV_ROUND_CLOSEST(priv->clock,
+ quot * baud);
+ if (samplecount != 0) {
+ realbaud = priv->clock / samplecount / quot;
+ if ((realbaud > BAUD_ALLOW_MAX(baud)) ||
+ (realbaud < BAUD_ALLOW_MIX(baud))) {
+ pr_info("baud %d can't be handled\n",
+ baud);
+ }
+ } else {
+ pr_info("samplecount is 0\n");
+ }
+ }
+ } else if (baud <= 576000) {
+ writel(2, &priv->regs->highspeed);
+
+ /* Set to next lower baudrate supported */
+ if ((baud == 500000) || (baud == 576000))
+ baud = 460800;
+ quot = DIV_ROUND_UP(priv->clock, 4 * baud);
+ } else {
+ writel(3, &priv->regs->highspeed);
+ quot = DIV_ROUND_UP(priv->clock, 256 * baud);
+ }
+
+ /* set divisor */
+ writel(UART_LCR_WLS_8 | UART_LCR_DLAB, &priv->regs->lcr);
+ writel(quot & 0xff, &priv->regs->dll);
+ writel((quot >> 8) & 0xff, &priv->regs->dlm);
+ writel(UART_LCR_WLS_8, &priv->regs->lcr);
+
+ if (baud > 460800) {
+ u32 tmp;
+
+ tmp = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
+ writel(tmp - 1, &priv->regs->sample_count);
+ writel((tmp - 2) >> 1, &priv->regs->sample_point);
+ } else {
+ writel(0, &priv->regs->sample_count);
+ writel(0xff, &priv->regs->sample_point);
+ }
+
+ if (support_clk12m_baud115200) {
+ writel(samplecount - 1, &priv->regs->sample_count);
+ writel((samplecount - 2) >> 1, &priv->regs->sample_point);
+ }
+}
+
+static int mtk_serial_setbrg(struct udevice *dev, int baudrate)
+{
+ struct mtk_serial_priv *priv = dev_get_priv(dev);
+
+ _mtk_serial_setbrg(priv, baudrate);
+
+ return 0;
+}
+
+static int mtk_serial_putc(struct udevice *dev, const char ch)
+{
+ struct mtk_serial_priv *priv = dev_get_priv(dev);
+
+ if (!(readl(&priv->regs->lsr) & UART_LSR_THRE))
+ return -EAGAIN;
+
+ writel(ch, &priv->regs->thr);
+
+ if (ch == '\n')
+ WATCHDOG_RESET();
+
+ return 0;
+}
+
+static int mtk_serial_getc(struct udevice *dev)
+{
+ struct mtk_serial_priv *priv = dev_get_priv(dev);
+
+ if (!(readl(&priv->regs->lsr) & UART_LSR_DR))
+ return -EAGAIN;
+
+ return readl(&priv->regs->rbr);
+}
+
+static int mtk_serial_pending(struct udevice *dev, bool input)
+{
+ struct mtk_serial_priv *priv = dev_get_priv(dev);
+
+ if (input)
+ return (readl(&priv->regs->lsr) & UART_LSR_DR) ? 1 : 0;
+ else
+ return (readl(&priv->regs->lsr) & UART_LSR_THRE) ? 0 : 1;
+}
+
+static int mtk_serial_probe(struct udevice *dev)
+{
+ struct mtk_serial_priv *priv = dev_get_priv(dev);
+
+ /* Disable interrupt */
+ writel(0, &priv->regs->ier);
+
+ return 0;
+}
+
+static int mtk_serial_ofdata_to_platdata(struct udevice *dev)
+{
+ struct mtk_serial_priv *priv = dev_get_priv(dev);
+ fdt_addr_t addr;
+ struct clk clk;
+ int err;
+
+ addr = dev_read_addr(dev);
+ if (addr == FDT_ADDR_T_NONE)
+ return -EINVAL;
+
+ priv->regs = map_physmem(addr, 0, MAP_NOCACHE);
+
+ err = clk_get_by_index(dev, 0, &clk);
+ if (!err) {
+ err = clk_get_rate(&clk);
+ if (!IS_ERR_VALUE(err))
+ priv->clock = err;
+ } else if (err != -ENOENT && err != -ENODEV && err != -ENOSYS) {
+ debug("mtk_serial: failed to get clock\n");
+ return err;
+ }
+
+ if (!priv->clock)
+ priv->clock = dev_read_u32_default(dev, "clock-frequency", 0);
+
+ if (!priv->clock) {
+ debug("mtk_serial: clock not defined\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static const struct dm_serial_ops mtk_serial_ops = {
+ .putc = mtk_serial_putc,
+ .pending = mtk_serial_pending,
+ .getc = mtk_serial_getc,
+ .setbrg = mtk_serial_setbrg,
+};
+
+static const struct udevice_id mtk_serial_ids[] = {
+ { .compatible = "mediatek,hsuart" },
+ { .compatible = "mediatek,mt6577-uart" },
+ { }
+};
+
+U_BOOT_DRIVER(serial_mtk) = {
+ .name = "serial_mtk",
+ .id = UCLASS_SERIAL,
+ .of_match = mtk_serial_ids,
+ .ofdata_to_platdata = mtk_serial_ofdata_to_platdata,
+ .priv_auto_alloc_size = sizeof(struct mtk_serial_priv),
+ .probe = mtk_serial_probe,
+ .ops = &mtk_serial_ops,
+ .flags = DM_FLAG_PRE_RELOC,
+};
+
+#ifdef CONFIG_DEBUG_UART_MTK
+
+#include <debug_uart.h>
+
+static inline void _debug_uart_init(void)
+{
+ struct mtk_serial_priv priv;
+
+ priv.regs = (void *) CONFIG_DEBUG_UART_BASE;
+ priv.clock = CONFIG_DEBUG_UART_CLOCK;
+
+ writel(0, &priv.regs->ier);
+
+ _mtk_serial_setbrg(&priv, CONFIG_BAUDRATE);
+}
+
+static inline void _debug_uart_putc(int ch)
+{
+ struct mtk_serial_regs __iomem *regs =
+ (void *) CONFIG_DEBUG_UART_BASE;
+
+ while (!(readl(®s->lsr) & UART_LSR_THRE))
+ ;
+
+ writel(ch, ®s->thr);
+}
+
+DEBUG_UART_FUNCS
+
+#endif
\ No newline at end of file