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 int iir;
  34         struct uart_8250_port *up = up_to_u8250p(port);
  35
  36         spin_lock(&up->port.lock);
  37
  38         iir = port->serial_in(port, UART_IIR);
  39         if (iir & UART_IIR_NO_INT) {
  40                 spin_unlock(&up->port.lock);
  41                 return 0;
  42         }
  43
  44         /* This is the WAR; if last event was BRK, then read and return */
  45         if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
  46                 up->lsr_saved_flags &= ~UART_LSR_BI;
  47                 port->serial_in(port, UART_RX);
  48                 spin_unlock(&up->port.lock);
  49                 return 1;
  50         }
  51
  52         lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
  53
  54         /* Process incoming characters first */
  55         if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
  56             (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
  57                 lsr = serial8250_rx_chars(up, lsr);
  58         }
  59
  60         /* Stop processing interrupts on input overrun */
  61         if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
  62                 unsigned long delay;
  63
  64                 up->ier = port->serial_in(port, UART_IER);
  65                 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
  66                         port->ops->stop_rx(port);
  67                 } else {
  68                         /* Keep restarting the timer until
  69                          * the input overrun subsides.
  70                          */
  71                         cancel_delayed_work(&up->overrun_backoff);
  72                 }
  73
  74                 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
  75                 schedule_delayed_work(&up->overrun_backoff, delay);
  76         }
  77
  78         serial8250_modem_status(up);
  79
  80         if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
  81                 serial8250_tx_chars(up);
  82
  83         up->lsr_saved_flags = orig_lsr;
  84
  85         uart_unlock_and_check_sysrq(&up->port);
  86
  87         return 1;
  88 }
  89 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
  90
  91 #ifdef CONFIG_ACPI
  92 static int fsl8250_acpi_probe(struct platform_device *pdev)
  93 {
  94         struct fsl8250_data *data;
  95         struct uart_8250_port port8250;
  96         struct device *dev = &pdev->dev;
  97         struct resource *regs;
  98
  99         int ret, irq;
 100
 101         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 102         if (!regs) {
 103                 dev_err(dev, "no registers defined\n");
 104                 return -EINVAL;
 105         }
 106
 107         irq = platform_get_irq(pdev, 0);
 108         if (irq < 0)
 109                 return irq;
 110
 111         memset(&port8250, 0, sizeof(port8250));
 112
 113         ret = device_property_read_u32(dev, "clock-frequency",
 114                                         &port8250.port.uartclk);
 115         if (ret)
 116                 return ret;
 117
 118         spin_lock_init(&port8250.port.lock);
 119
 120         port8250.port.mapbase           = regs->start;
 121         port8250.port.irq               = irq;
 122         port8250.port.handle_irq        = fsl8250_handle_irq;
 123         port8250.port.type              = PORT_16550A;
 124         port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
 125                                                 | UPF_FIXED_PORT | UPF_IOREMAP
 126                                                 | UPF_FIXED_TYPE;
 127         port8250.port.dev               = dev;
 128         port8250.port.mapsize           = resource_size(regs);
 129         port8250.port.iotype            = UPIO_MEM;
 130         port8250.port.irqflags          = IRQF_SHARED;
 131
 132         port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
 133                                                         port8250.port.mapsize);
 134         if (!port8250.port.membase)
 135                 return -ENOMEM;
 136
 137         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 138         if (!data)
 139                 return -ENOMEM;
 140
 141         data->line = serial8250_register_8250_port(&port8250);
 142         if (data->line < 0)
 143                 return data->line;
 144
 145         platform_set_drvdata(pdev, data);
 146         return 0;
 147 }
 148
 149 static int fsl8250_acpi_remove(struct platform_device *pdev)
 150 {
 151         struct fsl8250_data *data = platform_get_drvdata(pdev);
 152
 153         serial8250_unregister_port(data->line);
 154         return 0;
 155 }
 156
 157 static const struct acpi_device_id fsl_8250_acpi_id[] = {
 158         { "NXP0018", 0 },
 159         { },
 160 };
 161 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
 162
 163 static struct platform_driver fsl8250_platform_driver = {
 164         .driver = {
 165                 .name                   = "fsl-16550-uart",
 166                 .acpi_match_table       = ACPI_PTR(fsl_8250_acpi_id),
 167         },
 168         .probe                  = fsl8250_acpi_probe,
 169         .remove                 = fsl8250_acpi_remove,
 170 };
 171
 172 module_platform_driver(fsl8250_platform_driver);
 173 #endif