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![Johan Hovold](/assets/img/avatar_default.png)
The 8250 handle_irq callback is not just called from the interrupt
handler but also from a timer callback when polling (e.g. for ports
without an interrupt line). Consequently the callback must explicitly
disable interrupts to avoid a potential deadlock with another interrupt
in polled mode.
Add back an irqrestore-version of the sysrq port-unlock helper and use
it in the 8250 callbacks that need it.
Fixes: 75f4e830fa
("serial: do not restore interrupt state in sysrq helper")
Cc: stable@vger.kernel.org # 5.13
Cc: Joel Stanley <joel@jms.id.au>
Cc: Andrew Jeffery <andrew@aj.id.au>
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210714080427.28164-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
174 lines
4.4 KiB
C
174 lines
4.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
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* Copyright 2020 NXP
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* Copyright 2020 Puresoftware Ltd.
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*
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* This isn't a full driver; it just provides an alternate IRQ
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* handler to deal with an errata and provide ACPI wrapper.
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* Everything else is just using the bog standard 8250 support.
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*
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* We follow code flow of serial8250_default_handle_irq() but add
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* a check for a break and insert a dummy read on the Rx for the
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* immediately following IRQ event.
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*
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* We re-use the already existing "bug handling" lsr_saved_flags
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* field to carry the "what we just did" information from the one
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* IRQ event to the next one.
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*/
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#include <linux/acpi.h>
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#include <linux/serial_reg.h>
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#include <linux/serial_8250.h>
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#include "8250.h"
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struct fsl8250_data {
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int line;
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};
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int fsl8250_handle_irq(struct uart_port *port)
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{
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unsigned char lsr, orig_lsr;
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unsigned long flags;
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unsigned int iir;
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struct uart_8250_port *up = up_to_u8250p(port);
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spin_lock_irqsave(&up->port.lock, flags);
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iir = port->serial_in(port, UART_IIR);
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if (iir & UART_IIR_NO_INT) {
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spin_unlock(&up->port.lock);
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return 0;
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}
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/* This is the WAR; if last event was BRK, then read and return */
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if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
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up->lsr_saved_flags &= ~UART_LSR_BI;
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port->serial_in(port, UART_RX);
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spin_unlock(&up->port.lock);
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return 1;
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}
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lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
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/* Process incoming characters first */
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if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
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(up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
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lsr = serial8250_rx_chars(up, lsr);
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}
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/* Stop processing interrupts on input overrun */
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if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
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unsigned long delay;
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up->ier = port->serial_in(port, UART_IER);
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if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
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port->ops->stop_rx(port);
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} else {
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/* Keep restarting the timer until
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* the input overrun subsides.
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*/
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cancel_delayed_work(&up->overrun_backoff);
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}
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delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
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schedule_delayed_work(&up->overrun_backoff, delay);
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}
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serial8250_modem_status(up);
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if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
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serial8250_tx_chars(up);
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up->lsr_saved_flags = orig_lsr;
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uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
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return 1;
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}
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EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
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#ifdef CONFIG_ACPI
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static int fsl8250_acpi_probe(struct platform_device *pdev)
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{
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struct fsl8250_data *data;
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struct uart_8250_port port8250;
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struct device *dev = &pdev->dev;
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struct resource *regs;
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int ret, irq;
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regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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if (!regs) {
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dev_err(dev, "no registers defined\n");
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return -EINVAL;
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}
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irq = platform_get_irq(pdev, 0);
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if (irq < 0)
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return irq;
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memset(&port8250, 0, sizeof(port8250));
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ret = device_property_read_u32(dev, "clock-frequency",
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&port8250.port.uartclk);
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if (ret)
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return ret;
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spin_lock_init(&port8250.port.lock);
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port8250.port.mapbase = regs->start;
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port8250.port.irq = irq;
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port8250.port.handle_irq = fsl8250_handle_irq;
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port8250.port.type = PORT_16550A;
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port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
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| UPF_FIXED_PORT | UPF_IOREMAP
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| UPF_FIXED_TYPE;
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port8250.port.dev = dev;
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port8250.port.mapsize = resource_size(regs);
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port8250.port.iotype = UPIO_MEM;
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port8250.port.irqflags = IRQF_SHARED;
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port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase,
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port8250.port.mapsize);
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if (!port8250.port.membase)
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return -ENOMEM;
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data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->line = serial8250_register_8250_port(&port8250);
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if (data->line < 0)
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return data->line;
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platform_set_drvdata(pdev, data);
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return 0;
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}
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static int fsl8250_acpi_remove(struct platform_device *pdev)
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{
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struct fsl8250_data *data = platform_get_drvdata(pdev);
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serial8250_unregister_port(data->line);
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return 0;
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}
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static const struct acpi_device_id fsl_8250_acpi_id[] = {
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{ "NXP0018", 0 },
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{ },
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};
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MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
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static struct platform_driver fsl8250_platform_driver = {
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.driver = {
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.name = "fsl-16550-uart",
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.acpi_match_table = ACPI_PTR(fsl_8250_acpi_id),
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},
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.probe = fsl8250_acpi_probe,
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.remove = fsl8250_acpi_remove,
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};
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module_platform_driver(fsl8250_platform_driver);
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#endif
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