u-boot/drivers/serial/serial_bcm283x_mu.c
Alexander Graf 9dfeffe2f9 serial_bcm283x_mu: Fail loading if not muxed
The bcm283x mini-uart is only really usable as U-Boot serial output
when it is muxed to the UART pins of the RPi pin header.

So fail probing in case it is not muxed correctly, as in that case
firmware did not initialize it properly either.

Signed-off-by: Alexander Graf <agraf@suse.de>
2018-01-28 12:27:34 -05:00

199 lines
4.5 KiB
C

/*
* (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
*
* Derived from pl01x code:
*
* (C) Copyright 2000
* Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
*
* (C) Copyright 2004
* ARM Ltd.
* Philippe Robin, <philippe.robin@arm.com>
*
* SPDX-License-Identifier: GPL-2.0+
*/
/* Simple U-Boot driver for the BCM283x mini UART */
#include <common.h>
#include <dm.h>
#include <errno.h>
#include <watchdog.h>
#include <asm/gpio.h>
#include <asm/io.h>
#include <serial.h>
#include <dm/platform_data/serial_bcm283x_mu.h>
#include <dm/pinctrl.h>
#include <linux/compiler.h>
struct bcm283x_mu_regs {
u32 io;
u32 iir;
u32 ier;
u32 lcr;
u32 mcr;
u32 lsr;
u32 msr;
u32 scratch;
u32 cntl;
u32 stat;
u32 baud;
};
#define BCM283X_MU_LCR_DATA_SIZE_8 3
#define BCM283X_MU_LSR_TX_IDLE BIT(6)
/* This actually means not full, but is named not empty in the docs */
#define BCM283X_MU_LSR_TX_EMPTY BIT(5)
#define BCM283X_MU_LSR_RX_READY BIT(0)
struct bcm283x_mu_priv {
struct bcm283x_mu_regs *regs;
};
static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
{
struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
struct bcm283x_mu_priv *priv = dev_get_priv(dev);
struct bcm283x_mu_regs *regs = priv->regs;
u32 divider;
if (plat->skip_init)
return 0;
divider = plat->clock / (baudrate * 8);
writel(BCM283X_MU_LCR_DATA_SIZE_8, &regs->lcr);
writel(divider - 1, &regs->baud);
return 0;
}
static int bcm283x_mu_serial_probe(struct udevice *dev)
{
struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
struct bcm283x_mu_priv *priv = dev_get_priv(dev);
priv->regs = (struct bcm283x_mu_regs *)plat->base;
return 0;
}
static int bcm283x_mu_serial_getc(struct udevice *dev)
{
struct bcm283x_mu_priv *priv = dev_get_priv(dev);
struct bcm283x_mu_regs *regs = priv->regs;
u32 data;
/* Wait until there is data in the FIFO */
if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
return -EAGAIN;
data = readl(&regs->io);
return (int)data;
}
static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
{
struct bcm283x_mu_priv *priv = dev_get_priv(dev);
struct bcm283x_mu_regs *regs = priv->regs;
/* Wait until there is space in the FIFO */
if (!(readl(&regs->lsr) & BCM283X_MU_LSR_TX_EMPTY))
return -EAGAIN;
/* Send the character */
writel(data, &regs->io);
return 0;
}
static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
{
struct bcm283x_mu_priv *priv = dev_get_priv(dev);
struct bcm283x_mu_regs *regs = priv->regs;
unsigned int lsr;
lsr = readl(&regs->lsr);
if (input) {
WATCHDOG_RESET();
return (lsr & BCM283X_MU_LSR_RX_READY) ? 1 : 0;
} else {
return (lsr & BCM283X_MU_LSR_TX_IDLE) ? 0 : 1;
}
}
static const struct dm_serial_ops bcm283x_mu_serial_ops = {
.putc = bcm283x_mu_serial_putc,
.pending = bcm283x_mu_serial_pending,
.getc = bcm283x_mu_serial_getc,
.setbrg = bcm283x_mu_serial_setbrg,
};
#if CONFIG_IS_ENABLED(OF_CONTROL)
static const struct udevice_id bcm283x_mu_serial_id[] = {
{.compatible = "brcm,bcm2835-aux-uart"},
{}
};
/*
* Check if this serial device is muxed
*
* The serial device will only work properly if it has been muxed to the serial
* pins by firmware. Check whether that happened here.
*
* @return true if serial device is muxed, false if not
*/
static bool bcm283x_is_serial_muxed(void)
{
int serial_gpio = 15;
struct udevice *dev;
if (uclass_first_device(UCLASS_PINCTRL, &dev) || !dev)
return false;
if (pinctrl_get_gpio_mux(dev, 0, serial_gpio) != BCM2835_GPIO_ALT5)
return false;
return true;
}
static int bcm283x_mu_serial_ofdata_to_platdata(struct udevice *dev)
{
struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
fdt_addr_t addr;
/* Don't spawn the device if it's not muxed */
if (!bcm283x_is_serial_muxed())
return -ENODEV;
addr = devfdt_get_addr(dev);
if (addr == FDT_ADDR_T_NONE)
return -EINVAL;
plat->base = addr;
plat->clock = dev_read_u32_default(dev, "clock", 1);
/*
* TODO: Reinitialization doesn't always work for now, just skip
* init always - we know we're already initialized
*/
plat->skip_init = true;
return 0;
}
#endif
U_BOOT_DRIVER(serial_bcm283x_mu) = {
.name = "serial_bcm283x_mu",
.id = UCLASS_SERIAL,
.of_match = of_match_ptr(bcm283x_mu_serial_id),
.ofdata_to_platdata = of_match_ptr(bcm283x_mu_serial_ofdata_to_platdata),
.platdata_auto_alloc_size = sizeof(struct bcm283x_mu_serial_platdata),
.probe = bcm283x_mu_serial_probe,
.ops = &bcm283x_mu_serial_ops,
.flags = DM_FLAG_PRE_RELOC,
.priv_auto_alloc_size = sizeof(struct bcm283x_mu_priv),
};