drivers/tty/serial/8250/8250_fsl.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
   4  * Copyright 2020 NXP
   5  * Copyright 2020 Puresoftware Ltd.
   6  *
   7  * This isn't a full driver; it just provides an alternate IRQ
   8  * handler to deal with an errata and provide ACPI wrapper.
   9  * Everything else is just using the bog standard 8250 support.
  10  *
  11  * We follow code flow of serial8250_default_handle_irq() but add
  12  * a check for a break and insert a dummy read on the Rx for the
  13  * immediately following IRQ event.
  14  *
  15  * We re-use the already existing "bug handling" lsr_saved_flags
  16  * field to carry the "what we just did" information from the one
  17  * IRQ event to the next one.
  18  */
  19
  20 #include <linux/acpi.h>
  21 #include <linux/serial_reg.h>
  22 #include <linux/serial_8250.h>
  23
  24 #include "8250.h"
  25
  26 int fsl8250_handle_irq(struct uart_port *port)
  27 {
  28         unsigned long flags;
  29         u16 lsr, orig_lsr;
  30         unsigned int iir;
  31         struct uart_8250_port *up = up_to_u8250p(port);
  32
  33         spin_lock_irqsave(&up->port.lock, flags);
  34
  35         iir = port->serial_in(port, UART_IIR);
  36         if (iir & UART_IIR_NO_INT) {
  37                 spin_unlock_irqrestore(&up->port.lock, flags);
  38                 return 0;
  39         }
  40
  41         /* This is the WAR; if last event was BRK, then read and return */
  42         if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
  43                 up->lsr_saved_flags &= ~UART_LSR_BI;
  44                 port->serial_in(port, UART_RX);
  45                 spin_unlock_irqrestore(&up->port.lock, flags);
  46                 return 1;
  47         }
  48
  49         lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
  50
  51         /* Process incoming characters first */
  52         if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
  53             (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
  54                 lsr = serial8250_rx_chars(up, lsr);
  55         }
  56
  57         /* Stop processing interrupts on input overrun */
  58         if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
  59                 unsigned long delay;
  60
  61                 up->ier = port->serial_in(port, UART_IER);
  62                 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
  63                         port->ops->stop_rx(port);
  64                 } else {
  65                         /* Keep restarting the timer until
  66                          * the input overrun subsides.
  67                          */
  68                         cancel_delayed_work(&up->overrun_backoff);
  69                 }
  70
  71                 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
  72                 schedule_delayed_work(&up->overrun_backoff, delay);
  73         }
  74
  75         serial8250_modem_status(up);
  76
  77         if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
  78                 serial8250_tx_chars(up);
  79
  80         up->lsr_saved_flags |= orig_lsr & UART_LSR_BI;
  81
  82         uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
  83
  84         return 1;
  85 }
  86 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
  87
  88 #ifdef CONFIG_ACPI
  89 struct fsl8250_data {
  90         int     line;
  91 };
  92
  93 static int fsl8250_acpi_probe(struct platform_device *pdev)
  94 {
  95         struct fsl8250_data *data;
  96         struct uart_8250_port port8250;
  97         struct device *dev = &pdev->dev;
  98         struct resource *regs;
  99
 100         int ret, irq;
 101
 102         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 103         if (!regs) {
 104                 dev_err(dev, "no registers defined\n");
 105                 return -EINVAL;
 106         }
 107
 108         irq = platform_get_irq(pdev, 0);
 109         if (irq < 0)
 110                 return irq;
 111
 112         memset(&port8250, 0, sizeof(port8250));
 113
 114         ret = device_property_read_u32(dev, "clock-frequency",
 115                                         &port8250.port.uartclk);
 116         if (ret)
 117                 return ret;
 118
 119         spin_lock_init(&port8250.port.lock);
 120
 121         port8250.port.mapbase           = regs->start;
 122         port8250.port.irq               = irq;
 123         port8250.port.handle_irq        = fsl8250_handle_irq;
 124         port8250.port.type              = PORT_16550A;
 125         port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
 126                                                 | UPF_FIXED_PORT | UPF_IOREMAP
 127                                                 | UPF_FIXED_TYPE;
 128         port8250.port.dev               = dev;
 129         port8250.port.mapsize           = resource_size(regs);
 130         port8250.port.iotype            = UPIO_MEM;
 131         port8250.port.irqflags          = IRQF_SHARED;
 132
 133         port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
 134                                                         port8250.port.mapsize);
 135         if (!port8250.port.membase)
 136                 return -ENOMEM;
 137
 138         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 139         if (!data)
 140                 return -ENOMEM;
 141
 142         data->line = serial8250_register_8250_port(&port8250);
 143         if (data->line < 0)
 144                 return data->line;
 145
 146         platform_set_drvdata(pdev, data);
 147         return 0;
 148 }
 149
 150 static int fsl8250_acpi_remove(struct platform_device *pdev)
 151 {
 152         struct fsl8250_data *data = platform_get_drvdata(pdev);
 153
 154         serial8250_unregister_port(data->line);
 155         return 0;
 156 }
 157
 158 static const struct acpi_device_id fsl_8250_acpi_id[] = {
 159         { "NXP0018", 0 },
 160         { },
 161 };
 162 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
 163
 164 static struct platform_driver fsl8250_platform_driver = {
 165         .driver = {
 166                 .name                   = "fsl-16550-uart",
 167                 .acpi_match_table       = ACPI_PTR(fsl_8250_acpi_id),
 168         },
 169         .probe                  = fsl8250_acpi_probe,
 170         .remove                 = fsl8250_acpi_remove,
 171 };
 172
 173 module_platform_driver(fsl8250_platform_driver);
 174 #endif