u-boot/drivers/serial/serial_mvebu_a3700.c

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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2016 Stefan Roese <sr@denx.de>
*/
#include <common.h>
#include <clk.h>
#include <dm.h>
#include <serial.h>
#include <asm/io.h>
#include <asm/arch/cpu.h>
struct mvebu_plat {
void __iomem *base;
ulong tbg_rate;
u8 tbg_idx;
};
/*
* Register offset
*/
#define UART_RX_REG 0x00
#define UART_TX_REG 0x04
#define UART_CTRL_REG 0x08
#define UART_STATUS_REG 0x0c
#define UART_BAUD_REG 0x10
#define UART_POSSR_REG 0x14
#define UART_STATUS_RX_RDY 0x10
#define UART_STATUS_TX_EMPTY 0x40
#define UART_STATUS_TXFIFO_FULL 0x800
#define UART_CTRL_RXFIFO_RESET 0x4000
#define UART_CTRL_TXFIFO_RESET 0x8000
static int mvebu_serial_putc(struct udevice *dev, const char ch)
{
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
while (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
;
writel(ch, base + UART_TX_REG);
return 0;
}
static int mvebu_serial_getc(struct udevice *dev)
{
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
while (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
;
return readl(base + UART_RX_REG) & 0xff;
}
static int mvebu_serial_pending(struct udevice *dev, bool input)
{
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
if (input) {
if (readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY)
return 1;
} else {
if (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY))
return 1;
}
return 0;
}
static int mvebu_serial_setbrg(struct udevice *dev, int baudrate)
{
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
u32 divider, d1, d2;
u32 oversampling;
/*
* Calculate divider
* baudrate = clock / 16 / divider
*/
d1 = d2 = 1;
divider = DIV_ROUND_CLOSEST(plat->tbg_rate, baudrate * 16 * d1 * d2);
/*
* Set Programmable Oversampling Stack to 0,
* UART defaults to 16x scheme
*/
oversampling = 0;
if (divider < 1)
divider = 1;
else if (divider > 1023) {
/*
* If divider is too high for selected baudrate then set
* divider d1 to the maximal value 6.
*/
d1 = 6;
divider = DIV_ROUND_CLOSEST(plat->tbg_rate,
baudrate * 16 * d1 * d2);
if (divider < 1)
divider = 1;
else if (divider > 1023) {
/*
* If divider is still too high then set also divider
* d2 to the maximal value 6.
*/
d2 = 6;
divider = DIV_ROUND_CLOSEST(plat->tbg_rate,
baudrate * 16 * d1 * d2);
if (divider < 1)
divider = 1;
else if (divider > 1023) {
/*
* And if divider is still to high then
* use oversampling with maximal factor 63.
*/
oversampling = (63 << 0) | (63 << 8) |
(63 << 16) | (63 << 24);
divider = DIV_ROUND_CLOSEST(plat->tbg_rate,
baudrate * 63 * d1 * d2);
if (divider < 1)
divider = 1;
else if (divider > 1023)
divider = 1023;
}
}
}
divider |= BIT(19); /* Do not use XTAL as a base clock */
divider |= d1 << 15; /* Set d1 divider */
divider |= d2 << 12; /* Set d2 divider */
divider |= plat->tbg_idx << 10; /* Use selected TBG as a base clock */
while (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY))
;
writel(divider, base + UART_BAUD_REG);
writel(oversampling, base + UART_POSSR_REG);
return 0;
}
static int mvebu_serial_probe(struct udevice *dev)
{
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
struct udevice *nb_clk;
ofnode nb_clk_node;
int i, res;
nb_clk_node = ofnode_by_compatible(ofnode_null(),
"marvell,armada-3700-periph-clock-nb");
if (!ofnode_valid(nb_clk_node)) {
printf("%s: NB periph clock node not available\n", __func__);
return -ENODEV;
}
res = device_get_global_by_ofnode(nb_clk_node, &nb_clk);
if (res) {
printf("%s: Cannot get NB periph clock\n", __func__);
return res;
}
/*
* Choose the TBG clock with lowest frequency which allows to configure
* UART also at lower baudrates.
*/
for (i = 0; i < 4; i++) {
struct clk clk;
ulong rate;
res = clk_get_by_index_nodev(nb_clk_node, i, &clk);
if (res) {
printf("%s: Cannot get TBG clock %i: %i\n", __func__,
i, res);
return -ENODEV;
}
rate = clk_get_rate(&clk);
if (!rate || IS_ERR_VALUE(rate)) {
printf("%s: Cannot get rate for TBG clock %i\n",
__func__, i);
return -EINVAL;
}
if (!i || plat->tbg_rate > rate) {
plat->tbg_rate = rate;
plat->tbg_idx = i;
}
}
/* reset FIFOs */
writel(UART_CTRL_RXFIFO_RESET | UART_CTRL_TXFIFO_RESET,
base + UART_CTRL_REG);
/* No Parity, 1 Stop */
writel(0, base + UART_CTRL_REG);
return 0;
}
static int mvebu_serial_remove(struct udevice *dev)
{
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
ulong new_parent_rate, parent_rate;
u32 new_divider, divider;
u32 new_oversampling;
u32 oversampling;
u32 d1, d2;
/*
* Switch UART base clock back to XTAL because older Linux kernel
* expects it. Otherwise it does not calculate UART divisor correctly
* and therefore UART does not work in kernel.
*/
divider = readl(base + UART_BAUD_REG);
if (!(divider & BIT(19))) /* UART already uses XTAL */
return 0;
/* Read current divisors settings */
d1 = (divider >> 15) & 7;
d2 = (divider >> 12) & 7;
parent_rate = plat->tbg_rate;
divider &= 1023;
oversampling = readl(base + UART_POSSR_REG) & 63;
if (!oversampling)
oversampling = 16;
/* Calculate new divisor against XTAL clock without changing baudrate */
new_oversampling = 0;
new_parent_rate = get_ref_clk() * 1000000;
new_divider = DIV_ROUND_CLOSEST(new_parent_rate * divider * d1 * d2 *
oversampling, parent_rate * 16);
/*
* UART does not work reliably when XTAL divisor is smaller than 4.
* In this case we do not switch UART parent to XTAL. User either
* configured unsupported settings or has newer kernel with patches
* which allow usage of non-XTAL clock as a parent clock.
*/
if (new_divider < 4)
return 0;
/*
* If new divisor is larger than maximal supported, try to switch
* from default x16 scheme to oversampling with maximal factor 63.
*/
if (new_divider > 1023) {
new_oversampling = 63;
new_divider = DIV_ROUND_CLOSEST(new_parent_rate * divider * d1 *
d2 * oversampling,
parent_rate * new_oversampling);
if (new_divider < 4 || new_divider > 1023)
return 0;
}
while (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY))
;
writel(new_divider, base + UART_BAUD_REG);
writel(new_oversampling, base + UART_POSSR_REG);
return 0;
}
static int mvebu_serial_of_to_plat(struct udevice *dev)
{
struct mvebu_plat *plat = dev_get_plat(dev);
plat->base = dev_read_addr_ptr(dev);
return 0;
}
static const struct dm_serial_ops mvebu_serial_ops = {
.putc = mvebu_serial_putc,
.pending = mvebu_serial_pending,
.getc = mvebu_serial_getc,
.setbrg = mvebu_serial_setbrg,
};
static const struct udevice_id mvebu_serial_ids[] = {
{ .compatible = "marvell,armada-3700-uart" },
{ }
};
U_BOOT_DRIVER(serial_mvebu) = {
.name = "serial_mvebu",
.id = UCLASS_SERIAL,
.of_match = mvebu_serial_ids,
.of_to_plat = mvebu_serial_of_to_plat,
.plat_auto = sizeof(struct mvebu_plat),
.probe = mvebu_serial_probe,
.remove = mvebu_serial_remove,
.flags = DM_FLAG_OS_PREPARE,
.ops = &mvebu_serial_ops,
};
#ifdef CONFIG_DEBUG_MVEBU_A3700_UART
#include <debug_uart.h>
static inline void _debug_uart_init(void)
{
void __iomem *base = (void __iomem *)CONFIG_DEBUG_UART_BASE;
u32 baudrate, parent_rate, divider;
/* reset FIFOs */
writel(UART_CTRL_RXFIFO_RESET | UART_CTRL_TXFIFO_RESET,
base + UART_CTRL_REG);
/* No Parity, 1 Stop */
writel(0, base + UART_CTRL_REG);
/*
* Calculate divider
* baudrate = clock / 16 / divider
*/
baudrate = 115200;
parent_rate = get_ref_clk() * 1000000;
divider = DIV_ROUND_CLOSEST(parent_rate, baudrate * 16);
writel(divider, base + UART_BAUD_REG);
/*
* Set Programmable Oversampling Stack to 0,
* UART defaults to 16x scheme
*/
writel(0, base + UART_POSSR_REG);
}
static inline void _debug_uart_putc(int ch)
{
void __iomem *base = (void __iomem *)CONFIG_DEBUG_UART_BASE;
while (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
;
writel(ch, base + UART_TX_REG);
}
DEBUG_UART_FUNCS
#endif