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u-boot/drivers/serial/serial_mtk.c
Weijie Gao 6952209ef2 serial: mediatek: enable baudrate accuracy compensation 
The high-speed UART from MediaTek supports baudrate accuracy
compensation when using high-speed mode 3.

This is done by calculating the first digit of the fraction part of
sample count value. The fraction value will be then used as the
reference to insert 0 to 10 sample cycle(s) to one frame (assume
that frame format is 8n1, i.e. 10 bits per frame).

The fracdiv_[l/m] registers are used to determine whether a bit in one frame
should be inserted with one sample cycle.

With typical 40MHz source clock, the actual baudrates with/without
accuracy compensation are:

Ideal    w/o compensation w/ compensation
======== ================ ===============
9600     9603             9600
115200   114942           115207
921600   930232           921659
3000000  3076923          3007519

Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
2025-06-05 14:30:35 -06:00

511 lines
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// 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 <config.h>
#include <div64.h>
#include <dm.h>
#include <dm/device.h>
#include <dm/device_compat.h>
#include <errno.h>
#include <log.h>
#include <serial.h>
#include <watchdog.h>
#include <asm/global_data.h>
#include <asm/io.h>
#include <asm/types.h>
#include <linux/err.h>
#include <linux/printk.h>
struct mtk_serial_regs {
u32 rbr;
u32 ier;
u32 fcr;
u32 lcr;
u32 mcr;
u32 lsr;
u32 msr;
u32 scr;
u32 autobaud_en;
u32 highspeed;
u32 sample_count;
u32 sample_point;
u32 autobaud_reg;
u32 ratefix_ad;
u32 autobaud_sample;
u32 guard;
u32 escape_dat;
u32 escape_en;
u32 sleep_en;
u32 dma_en;
u32 rxtri_ad;
u32 fracdiv_l;
u32 fracdiv_m;
u32 fcr_rd;
};
#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 */
#define UART_LSR_TEMT 0x40 /* Xmitter empty */
#define UART_MCR_DTR 0x01 /* DTR */
#define UART_MCR_RTS 0x02 /* RTS */
#define UART_FCR_FIFO_EN 0x01 /* Fifo enable */
#define UART_FCR_RXSR 0x02 /* Receiver soft reset */
#define UART_FCR_TXSR 0x04 /* Transmitter soft reset */
#define UART_MCRVAL (UART_MCR_DTR | \
UART_MCR_RTS)
/* Clear & enable FIFOs */
#define UART_FCRVAL (UART_FCR_FIFO_EN | \
UART_FCR_RXSR | \
UART_FCR_TXSR)
/* 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 - Structure holding all information used by the
* driver
* @regs: Register base of the serial port
* @clk: The baud clock device
* @clk_bus: The bus clock device
* @fixed_clk_rate: Fallback fixed baud clock rate if baud clock
* device is not specified
* @force_highspeed: Force using high-speed mode
* @upstream_highspeed_logic: Apply upstream high-speed logic
*/
struct mtk_serial_priv {
struct mtk_serial_regs __iomem *regs;
struct clk clk;
struct clk clk_bus;
u32 fixed_clk_rate;
bool force_highspeed;
bool upstream_highspeed_logic;
};
static const unsigned short fraction_l_mapping[] = {
0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
};
static const unsigned short fraction_m_mapping[] = {
0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
};
static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud,
uint clk_rate)
{
u32 quot, realbaud, samplecount = 1, fraction, frac_l = 0, frac_m = 0;
/* Special case for low baud clock */
if (baud <= 115200 && clk_rate == 12000000) {
writel(3, &priv->regs->highspeed);
quot = DIV_ROUND_CLOSEST(clk_rate, 256 * baud);
if (quot == 0)
quot = 1;
samplecount = DIV_ROUND_CLOSEST(clk_rate, quot * baud);
realbaud = clk_rate / samplecount / quot;
if (realbaud > BAUD_ALLOW_MAX(baud) ||
realbaud < BAUD_ALLOW_MIX(baud)) {
pr_info("baud %d can't be handled\n", baud);
}
goto set_baud;
}
/*
* Upstream linux use highspeed for anything >= 115200 and lowspeed
* for < 115200. Simulate this if we are using the upstream compatible.
*/
if (priv->force_highspeed ||
(priv->upstream_highspeed_logic && baud >= 115200))
goto use_hs3;
if (baud <= 115200) {
writel(0, &priv->regs->highspeed);
quot = DIV_ROUND_CLOSEST(clk_rate, 16 * baud);
} 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(clk_rate, 4 * baud);
} else {
use_hs3:
writel(3, &priv->regs->highspeed);
quot = DIV_ROUND_UP(clk_rate, 256 * baud);
samplecount = clk_rate / (quot * baud);
fraction = ((clk_rate * 100) / quot / baud) % 100;
fraction = DIV_ROUND_CLOSEST(fraction, 10);
frac_l = fraction_l_mapping[fraction];
frac_m = fraction_m_mapping[fraction];
}
set_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);
/* set highspeed mode sample count & point */
writel(samplecount - 1, &priv->regs->sample_count);
writel((samplecount >> 1) - 1, &priv->regs->sample_point);
/* set baudrate fraction compensation */
writel(frac_l, &priv->regs->fracdiv_l);
writel(frac_m, &priv->regs->fracdiv_m);
}
static int _mtk_serial_putc(struct mtk_serial_priv *priv, const char ch)
{
if (!(readl(&priv->regs->lsr) & UART_LSR_THRE))
return -EAGAIN;
writel(ch, &priv->regs->thr);
if (ch == '\n')
schedule();
return 0;
}
static int _mtk_serial_getc(struct mtk_serial_priv *priv)
{
if (!(readl(&priv->regs->lsr) & UART_LSR_DR))
return -EAGAIN;
return readl(&priv->regs->rbr);
}
static int _mtk_serial_pending(struct mtk_serial_priv *priv, bool input)
{
if (input)
return (readl(&priv->regs->lsr) & UART_LSR_DR) ? 1 : 0;
else
return (readl(&priv->regs->lsr) & UART_LSR_THRE) ? 0 : 1;
}
#if CONFIG_IS_ENABLED(DM_SERIAL)
static int mtk_serial_setbrg(struct udevice *dev, int baudrate)
{
struct mtk_serial_priv *priv = dev_get_priv(dev);
u32 clk_rate;
clk_rate = clk_get_rate(&priv->clk);
if (IS_ERR_VALUE(clk_rate) || clk_rate == 0)
clk_rate = priv->fixed_clk_rate;
_mtk_serial_setbrg(priv, baudrate, clk_rate);
return 0;
}
static int mtk_serial_putc(struct udevice *dev, const char ch)
{
struct mtk_serial_priv *priv = dev_get_priv(dev);
return _mtk_serial_putc(priv, ch);
}
static int mtk_serial_getc(struct udevice *dev)
{
struct mtk_serial_priv *priv = dev_get_priv(dev);
return _mtk_serial_getc(priv);
}
static int mtk_serial_pending(struct udevice *dev, bool input)
{
struct mtk_serial_priv *priv = dev_get_priv(dev);
return _mtk_serial_pending(priv, input);
}
static int mtk_serial_probe(struct udevice *dev)
{
struct mtk_serial_priv *priv = dev_get_priv(dev);
/* Disable interrupt */
writel(0, &priv->regs->ier);
writel(UART_MCRVAL, &priv->regs->mcr);
writel(UART_FCRVAL, &priv->regs->fcr);
clk_enable(&priv->clk);
if (priv->clk_bus.dev)
clk_enable(&priv->clk_bus);
return 0;
}
static int mtk_serial_of_to_plat(struct udevice *dev)
{
struct mtk_serial_priv *priv = dev_get_priv(dev);
fdt_addr_t addr;
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, &priv->clk);
if (err) {
err = dev_read_u32(dev, "clock-frequency", &priv->fixed_clk_rate);
if (err) {
dev_err(dev, "baud clock not defined\n");
return -EINVAL;
}
} else {
err = clk_get_rate(&priv->clk);
if (IS_ERR_VALUE(err)) {
dev_err(dev, "invalid baud clock\n");
return -EINVAL;
}
}
clk_get_by_name(dev, "bus", &priv->clk_bus);
priv->force_highspeed = dev_read_bool(dev, "mediatek,force-highspeed");
priv->upstream_highspeed_logic =
device_is_compatible(dev, "mediatek,mt6577-uart");
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,
.of_to_plat = mtk_serial_of_to_plat,
.priv_auto = sizeof(struct mtk_serial_priv),
.probe = mtk_serial_probe,
.ops = &mtk_serial_ops,
.flags = DM_FLAG_PRE_RELOC,
};
#else
DECLARE_GLOBAL_DATA_PTR;
#define DECLARE_HSUART_PRIV(port) \
static struct mtk_serial_priv mtk_hsuart##port = { \
.regs = (struct mtk_serial_regs *)CFG_SYS_NS16550_COM##port, \
.fixed_clk_rate = CFG_SYS_NS16550_CLK \
};
#define DECLARE_HSUART_FUNCTIONS(port) \
static int mtk_serial##port##_init(void) \
{ \
writel(0, &mtk_hsuart##port.regs->ier); \
writel(UART_MCRVAL, &mtk_hsuart##port.regs->mcr); \
writel(UART_FCRVAL, &mtk_hsuart##port.regs->fcr); \
_mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate, \
mtk_hsuart##port.fixed_clk_rate); \
return 0 ; \
} \
static void mtk_serial##port##_setbrg(void) \
{ \
_mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate, \
mtk_hsuart##port.fixed_clk_rate); \
} \
static int mtk_serial##port##_getc(void) \
{ \
int err; \
do { \
err = _mtk_serial_getc(&mtk_hsuart##port); \
if (err == -EAGAIN) \
schedule(); \
} while (err == -EAGAIN); \
return err >= 0 ? err : 0; \
} \
static int mtk_serial##port##_tstc(void) \
{ \
return _mtk_serial_pending(&mtk_hsuart##port, true); \
} \
static void mtk_serial##port##_putc(const char c) \
{ \
int err; \
if (c == '\n') \
mtk_serial##port##_putc('\r'); \
do { \
err = _mtk_serial_putc(&mtk_hsuart##port, c); \
} while (err == -EAGAIN); \
} \
static void mtk_serial##port##_puts(const char *s) \
{ \
while (*s) { \
mtk_serial##port##_putc(*s++); \
} \
}
/* Serial device descriptor */
#define INIT_HSUART_STRUCTURE(port, __name) { \
.name = __name, \
.start = mtk_serial##port##_init, \
.stop = NULL, \
.setbrg = mtk_serial##port##_setbrg, \
.getc = mtk_serial##port##_getc, \
.tstc = mtk_serial##port##_tstc, \
.putc = mtk_serial##port##_putc, \
.puts = mtk_serial##port##_puts, \
}
#define DECLARE_HSUART(port, __name) \
DECLARE_HSUART_PRIV(port); \
DECLARE_HSUART_FUNCTIONS(port); \
struct serial_device mtk_hsuart##port##_device = \
INIT_HSUART_STRUCTURE(port, __name);
#if !defined(CONFIG_CONS_INDEX)
#elif (CONFIG_CONS_INDEX < 1) || (CONFIG_CONS_INDEX > 6)
#error "Invalid console index value."
#endif
#if CONFIG_CONS_INDEX == 1 && !defined(CFG_SYS_NS16550_COM1)
#error "Console port 1 defined but not configured."
#elif CONFIG_CONS_INDEX == 2 && !defined(CFG_SYS_NS16550_COM2)
#error "Console port 2 defined but not configured."
#elif CONFIG_CONS_INDEX == 3 && !defined(CFG_SYS_NS16550_COM3)
#error "Console port 3 defined but not configured."
#elif CONFIG_CONS_INDEX == 4 && !defined(CFG_SYS_NS16550_COM4)
#error "Console port 4 defined but not configured."
#elif CONFIG_CONS_INDEX == 5 && !defined(CFG_SYS_NS16550_COM5)
#error "Console port 5 defined but not configured."
#elif CONFIG_CONS_INDEX == 6 && !defined(CFG_SYS_NS16550_COM6)
#error "Console port 6 defined but not configured."
#endif
#if defined(CFG_SYS_NS16550_COM1)
DECLARE_HSUART(1, "mtk-hsuart0");
#endif
#if defined(CFG_SYS_NS16550_COM2)
DECLARE_HSUART(2, "mtk-hsuart1");
#endif
#if defined(CFG_SYS_NS16550_COM3)
DECLARE_HSUART(3, "mtk-hsuart2");
#endif
#if defined(CFG_SYS_NS16550_COM4)
DECLARE_HSUART(4, "mtk-hsuart3");
#endif
#if defined(CFG_SYS_NS16550_COM5)
DECLARE_HSUART(5, "mtk-hsuart4");
#endif
#if defined(CFG_SYS_NS16550_COM6)
DECLARE_HSUART(6, "mtk-hsuart5");
#endif
__weak struct serial_device *default_serial_console(void)
{
#if CONFIG_CONS_INDEX == 1
return &mtk_hsuart1_device;
#elif CONFIG_CONS_INDEX == 2
return &mtk_hsuart2_device;
#elif CONFIG_CONS_INDEX == 3
return &mtk_hsuart3_device;
#elif CONFIG_CONS_INDEX == 4
return &mtk_hsuart4_device;
#elif CONFIG_CONS_INDEX == 5
return &mtk_hsuart5_device;
#elif CONFIG_CONS_INDEX == 6
return &mtk_hsuart6_device;
#else
#error "Bad CONFIG_CONS_INDEX."
#endif
}
void mtk_serial_initialize(void)
{
#if defined(CFG_SYS_NS16550_COM1)
serial_register(&mtk_hsuart1_device);
#endif
#if defined(CFG_SYS_NS16550_COM2)
serial_register(&mtk_hsuart2_device);
#endif
#if defined(CFG_SYS_NS16550_COM3)
serial_register(&mtk_hsuart3_device);
#endif
#if defined(CFG_SYS_NS16550_COM4)
serial_register(&mtk_hsuart4_device);
#endif
#if defined(CFG_SYS_NS16550_COM5)
serial_register(&mtk_hsuart5_device);
#endif
#if defined(CFG_SYS_NS16550_COM6)
serial_register(&mtk_hsuart6_device);
#endif
}
#endif
#ifdef CONFIG_DEBUG_UART_MTK
#include <debug_uart.h>
static inline void _debug_uart_init(void)
{
struct mtk_serial_priv priv;
memset(&priv, 0, sizeof(struct mtk_serial_priv));
priv.regs = (void *) CONFIG_VAL(DEBUG_UART_BASE);
priv.fixed_clk_rate = CONFIG_DEBUG_UART_CLOCK;
writel(0, &priv.regs->ier);
writel(UART_MCRVAL, &priv.regs->mcr);
writel(UART_FCRVAL, &priv.regs->fcr);
_mtk_serial_setbrg(&priv, CONFIG_BAUDRATE, priv.fixed_clk_rate);
}
static inline void _debug_uart_putc(int ch)
{
struct mtk_serial_regs __iomem *regs =
(void *) CONFIG_VAL(DEBUG_UART_BASE);
while (!(readl(&regs->lsr) & UART_LSR_THRE))
;
writel(ch, &regs->thr);
}
DEBUG_UART_FUNCS
#endif
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