serial/8250/8250_fsl.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
0004  * Copyright 2020 NXP
0005  * Copyright 2020 Puresoftware Ltd.
0006  *
0007  * This isn't a full driver; it just provides an alternate IRQ
0008  * handler to deal with an errata and provide ACPI wrapper.
0009  * Everything else is just using the bog standard 8250 support.
0010  *
0011  * We follow code flow of serial8250_default_handle_irq() but add
0012  * a check for a break and insert a dummy read on the Rx for the
0013  * immediately following IRQ event.
0014  *
0015  * We re-use the already existing "bug handling" lsr_saved_flags
0016  * field to carry the "what we just did" information from the one
0017  * IRQ event to the next one.
0018  */
0019
0020 #include <linux/acpi.h>
0021 #include <linux/serial_reg.h>
0022 #include <linux/serial_8250.h>
0023
0024 #include "8250.h"
0025
0026 int fsl8250_handle_irq(struct uart_port *port)
0027 {
0028     unsigned long flags;
0029     u16 lsr, orig_lsr;
0030     unsigned int iir;
0031     struct uart_8250_port *up = up_to_u8250p(port);
0032
0033     spin_lock_irqsave(&up->port.lock, flags);
0034
0035     iir = port->serial_in(port, UART_IIR);
0036     if (iir & UART_IIR_NO_INT) {
0037         spin_unlock(&up->port.lock);
0038         return 0;
0039     }
0040
0041     /* This is the WAR; if last event was BRK, then read and return */
0042     if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
0043         up->lsr_saved_flags &= ~UART_LSR_BI;
0044         port->serial_in(port, UART_RX);
0045         spin_unlock(&up->port.lock);
0046         return 1;
0047     }
0048
0049     lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
0050
0051     /* Process incoming characters first */
0052     if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
0053         (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
0054         lsr = serial8250_rx_chars(up, lsr);
0055     }
0056
0057     /* Stop processing interrupts on input overrun */
0058     if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
0059         unsigned long delay;
0060
0061         up->ier = port->serial_in(port, UART_IER);
0062         if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
0063             port->ops->stop_rx(port);
0064         } else {
0065             /* Keep restarting the timer until
0066              * the input overrun subsides.
0067              */
0068             cancel_delayed_work(&up->overrun_backoff);
0069         }
0070
0071         delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
0072         schedule_delayed_work(&up->overrun_backoff, delay);
0073     }
0074
0075     serial8250_modem_status(up);
0076
0077     if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
0078         serial8250_tx_chars(up);
0079
0080     up->lsr_saved_flags |= orig_lsr & UART_LSR_BI;
0081
0082     uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
0083
0084     return 1;
0085 }
0086 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
0087
0088 #ifdef CONFIG_ACPI
0089 struct fsl8250_data {
0090     int line;
0091 };
0092
0093 static int fsl8250_acpi_probe(struct platform_device *pdev)
0094 {
0095     struct fsl8250_data *data;
0096     struct uart_8250_port port8250;
0097     struct device *dev = &pdev->dev;
0098     struct resource *regs;
0099
0100     int ret, irq;
0101
0102     regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
0103     if (!regs) {
0104         dev_err(dev, "no registers defined\n");
0105         return -EINVAL;
0106     }
0107
0108     irq = platform_get_irq(pdev, 0);
0109     if (irq < 0)
0110         return irq;
0111
0112     memset(&port8250, 0, sizeof(port8250));
0113
0114     ret = device_property_read_u32(dev, "clock-frequency",
0115                     &port8250.port.uartclk);
0116     if (ret)
0117         return ret;
0118
0119     spin_lock_init(&port8250.port.lock);
0120
0121     port8250.port.mapbase           = regs->start;
0122     port8250.port.irq               = irq;
0123     port8250.port.handle_irq        = fsl8250_handle_irq;
0124     port8250.port.type              = PORT_16550A;
0125     port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
0126                         | UPF_FIXED_PORT | UPF_IOREMAP
0127                         | UPF_FIXED_TYPE;
0128     port8250.port.dev               = dev;
0129     port8250.port.mapsize           = resource_size(regs);
0130     port8250.port.iotype            = UPIO_MEM;
0131     port8250.port.irqflags          = IRQF_SHARED;
0132
0133     port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
0134                             port8250.port.mapsize);
0135     if (!port8250.port.membase)
0136         return -ENOMEM;
0137
0138     data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
0139     if (!data)
0140         return -ENOMEM;
0141
0142     data->line = serial8250_register_8250_port(&port8250);
0143     if (data->line < 0)
0144         return data->line;
0145
0146     platform_set_drvdata(pdev, data);
0147     return 0;
0148 }
0149
0150 static int fsl8250_acpi_remove(struct platform_device *pdev)
0151 {
0152     struct fsl8250_data *data = platform_get_drvdata(pdev);
0153
0154     serial8250_unregister_port(data->line);
0155     return 0;
0156 }
0157
0158 static const struct acpi_device_id fsl_8250_acpi_id[] = {
0159     { "NXP0018", 0 },
0160     { },
0161 };
0162 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
0163
0164 static struct platform_driver fsl8250_platform_driver = {
0165     .driver = {
0166         .name           = "fsl-16550-uart",
0167         .acpi_match_table   = ACPI_PTR(fsl_8250_acpi_id),
0168     },
0169     .probe          = fsl8250_acpi_probe,
0170     .remove         = fsl8250_acpi_remove,
0171 };
0172
0173 module_platform_driver(fsl8250_platform_driver);
0174 #endif