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 struct fsl8250_data {
  27         int     line;
  28 };
  29
  30 int fsl8250_handle_irq(struct uart_port *port)
  31 {
  32         unsigned char lsr, orig_lsr;
  33         unsigned long flags;
  34         unsigned int iir;
  35         struct uart_8250_port *up = up_to_u8250p(port);
  36
  37         spin_lock_irqsave(&up->port.lock, flags);
  38
  39         iir = port->serial_in(port, UART_IIR);
  40         if (iir & UART_IIR_NO_INT) {
  41                 spin_unlock_irqrestore(&up->port.lock, flags);
  42                 return 0;
  43         }
  44
  45         /* This is the WAR; if last event was BRK, then read and return */
  46         if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
  47                 up->lsr_saved_flags &= ~UART_LSR_BI;
  48                 port->serial_in(port, UART_RX);
  49                 spin_unlock_irqrestore(&up->port.lock, flags);
  50                 return 1;
  51         }
  52
  53         lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
  54
  55         /* Process incoming characters first */
  56         if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
  57             (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
  58                 lsr = serial8250_rx_chars(up, lsr);
  59         }
  60
  61         /* Stop processing interrupts on input overrun */
  62         if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
  63                 unsigned long delay;
  64
  65                 up->ier = port->serial_in(port, UART_IER);
  66                 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
  67                         port->ops->stop_rx(port);
  68                 } else {
  69                         /* Keep restarting the timer until
  70                          * the input overrun subsides.
  71                          */
  72                         cancel_delayed_work(&up->overrun_backoff);
  73                 }
  74
  75                 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
  76                 schedule_delayed_work(&up->overrun_backoff, delay);
  77         }
  78
  79         serial8250_modem_status(up);
  80
  81         if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
  82                 serial8250_tx_chars(up);
  83
  84         up->lsr_saved_flags = orig_lsr;
  85         uart_unlock_and_check_sysrq(&up->port, flags);
  86         return 1;
  87 }
  88 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
  89
  90 #ifdef CONFIG_ACPI
  91 static int fsl8250_acpi_probe(struct platform_device *pdev)
  92 {
  93         struct fsl8250_data *data;
  94         struct uart_8250_port port8250;
  95         struct device *dev = &pdev->dev;
  96         struct resource *regs;
  97
  98         int ret, irq;
  99
 100         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 101         if (!regs) {
 102                 dev_err(dev, "no registers defined\n");
 103                 return -EINVAL;
 104         }
 105
 106         irq = platform_get_irq(pdev, 0);
 107         if (irq < 0) {
 108                 if (irq != -EPROBE_DEFER)
 109                         dev_err(dev, "cannot get irq\n");
 110                 return irq;
 111         }
 112
 113         memset(&port8250, 0, sizeof(port8250));
 114
 115         ret = device_property_read_u32(dev, "clock-frequency",
 116                                         &port8250.port.uartclk);
 117         if (ret)
 118                 return ret;
 119
 120         spin_lock_init(&port8250.port.lock);
 121
 122         port8250.port.mapbase           = regs->start;
 123         port8250.port.irq               = irq;
 124         port8250.port.handle_irq        = fsl8250_handle_irq;
 125         port8250.port.type              = PORT_16550A;
 126         port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
 127                                                 | UPF_FIXED_PORT | UPF_IOREMAP
 128                                                 | UPF_FIXED_TYPE;
 129         port8250.port.dev               = dev;
 130         port8250.port.mapsize           = resource_size(regs);
 131         port8250.port.iotype            = UPIO_MEM;
 132         port8250.port.irqflags          = IRQF_SHARED;
 133
 134         port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
 135                                                         port8250.port.mapsize);
 136         if (!port8250.port.membase)
 137                 return -ENOMEM;
 138
 139         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 140         if (!data)
 141                 return -ENOMEM;
 142
 143         data->line = serial8250_register_8250_port(&port8250);
 144         if (data->line < 0)
 145                 return data->line;
 146
 147         platform_set_drvdata(pdev, data);
 148         return 0;
 149 }
 150
 151 static int fsl8250_acpi_remove(struct platform_device *pdev)
 152 {
 153         struct fsl8250_data *data = platform_get_drvdata(pdev);
 154
 155         serial8250_unregister_port(data->line);
 156         return 0;
 157 }
 158
 159 static const struct acpi_device_id fsl_8250_acpi_id[] = {
 160         { "NXP0018", 0 },
 161         { },
 162 };
 163 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
 164
 165 static struct platform_driver fsl8250_platform_driver = {
 166         .driver = {
 167                 .name                   = "fsl-16550-uart",
 168                 .acpi_match_table       = ACPI_PTR(fsl_8250_acpi_id),
 169         },
 170         .probe                  = fsl8250_acpi_probe,
 171         .remove                 = fsl8250_acpi_remove,
 172 };
 173
 174 module_platform_driver(fsl8250_platform_driver);
 175 #endif