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// SPDX-License-Identifier: GPL-2.0
/*
* Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
* Copyright 2020 NXP
* Copyright 2020 Puresoftware Ltd.
*
* This isn't a full driver; it just provides an alternate IRQ
* handler to deal with an errata and provide ACPI wrapper.
* Everything else is just using the bog standard 8250 support.
*
* We follow code flow of serial8250_default_handle_irq() but add
* a check for a break and insert a dummy read on the Rx for the
* immediately following IRQ event.
*
* We re-use the already existing "bug handling" lsr_saved_flags
* field to carry the "what we just did" information from the one
* IRQ event to the next one.
*/
#include <linux/acpi.h>
#include <linux/serial_reg.h>
#include <linux/serial_8250.h>
#include "8250.h"
int fsl8250_handle_irq(struct uart_port *port)
{
unsigned long flags;
u16 lsr, orig_lsr;
unsigned int iir;
struct uart_8250_port *up = up_to_u8250p(port);
uart_port_lock_irqsave(&up->port, &flags);
iir = port->serial_in(port, UART_IIR);
if (iir & UART_IIR_NO_INT) {
uart_port_unlock_irqrestore(&up->port, flags);
return 0;
}
/*
* For a single break the hardware reports LSR.BI for each character
* time. This is described in the MPC8313E chip errata as "General17".
* A typical break has a duration of 0.3s, with a 115200n8 configuration
* that (theoretically) corresponds to ~3500 interrupts in these 0.3s.
* In practise it's less (around 500) because of hardware
* and software latencies. The workaround recommended by the vendor is
* to read the RX register (to clear LSR.DR and thus prevent a FIFO
* aging interrupt). To prevent the irq from retriggering LSR must not be
* read. (This would clear LSR.BI, hardware would reassert the BI event
* immediately and interrupt the CPU again. The hardware clears LSR.BI
* when the next valid char is read.)
*/
if (unlikely((iir & UART_IIR_ID) == UART_IIR_RLSI &&
(up->lsr_saved_flags & UART_LSR_BI))) {
up->lsr_saved_flags &= ~UART_LSR_BI;
port->serial_in(port, UART_RX);
uart_port_unlock_irqrestore(&up->port, flags);
return 1;
}
lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
/* Process incoming characters first */
if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
(up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
lsr = serial8250_rx_chars(up, lsr);
}
/* Stop processing interrupts on input overrun */
if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
unsigned long delay;
up->ier = port->serial_in(port, UART_IER);
if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
port->ops->stop_rx(port);
} else {
/* Keep restarting the timer until
* the input overrun subsides.
*/
cancel_delayed_work(&up->overrun_backoff);
}
delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
schedule_delayed_work(&up->overrun_backoff, delay);
}
serial8250_modem_status(up);
if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
serial8250_tx_chars(up);
up->lsr_saved_flags |= orig_lsr & UART_LSR_BI;
uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
return 1;
}
EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
#ifdef CONFIG_ACPI
struct fsl8250_data {
int line;
};
static int fsl8250_acpi_probe(struct platform_device *pdev)
{
struct fsl8250_data *data;
struct uart_8250_port port8250;
struct device *dev = &pdev->dev;
struct resource *regs;
int ret, irq;
regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!regs) {
dev_err(dev, "no registers defined\n");
return -EINVAL;
}
irq = platform_get_irq(pdev, 0);
if (irq < 0)
return irq;
memset(&port8250, 0, sizeof(port8250));
ret = device_property_read_u32(dev, "clock-frequency",
&port8250.port.uartclk);
if (ret)
return ret;
spin_lock_init(&port8250.port.lock);
port8250.port.mapbase = regs->start;
port8250.port.irq = irq;
port8250.port.handle_irq = fsl8250_handle_irq;
port8250.port.type = PORT_16550A;
port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
| UPF_FIXED_PORT | UPF_IOREMAP
| UPF_FIXED_TYPE;
port8250.port.dev = dev;
port8250.port.mapsize = resource_size(regs);
port8250.port.iotype = UPIO_MEM;
port8250.port.irqflags = IRQF_SHARED;
port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase,
port8250.port.mapsize);
if (!port8250.port.membase)
return -ENOMEM;
data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->line = serial8250_register_8250_port(&port8250);
if (data->line < 0)
return data->line;
platform_set_drvdata(pdev, data);
return 0;
}
static void fsl8250_acpi_remove(struct platform_device *pdev)
{
struct fsl8250_data *data = platform_get_drvdata(pdev);
serial8250_unregister_port(data->line);
}
static const struct acpi_device_id fsl_8250_acpi_id[] = {
{ "NXP0018", 0 },
{ },
};
MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
static struct platform_driver fsl8250_platform_driver = {
.driver = {
.name = "fsl-16550-uart",
.acpi_match_table = ACPI_PTR(fsl_8250_acpi_id),
},
.probe = fsl8250_acpi_probe,
.remove = fsl8250_acpi_remove,
};
module_platform_driver(fsl8250_platform_driver);
#endif
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Handling of Freescale specific 8250 variants");
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