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         uart_port_lock_irqsave(&up->port, &flags);
  34
  35         iir = port->serial_in(port, UART_IIR);
  36         if (iir & UART_IIR_NO_INT) {
  37                 uart_port_unlock_irqrestore(&up->port, flags);
  38                 return 0;
  39         }
  40
  41         /*
  42          * For a single break the hardware reports LSR.BI for each character
  43          * time. This is described in the MPC8313E chip errata as "General17".
  44          * A typical break has a duration of 0.3s, with a 115200n8 configuration
  45          * that (theoretically) corresponds to ~3500 interrupts in these 0.3s.
  46          * In practise it's less (around 500) because of hardware
  47          * and software latencies. The workaround recommended by the vendor is
  48          * to read the RX register (to clear LSR.DR and thus prevent a FIFO
  49          * aging interrupt). To prevent the irq from retriggering LSR must not be
  50          * read. (This would clear LSR.BI, hardware would reassert the BI event
  51          * immediately and interrupt the CPU again. The hardware clears LSR.BI
  52          * when the next valid char is read.)
  53          */
  54         if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
  55                 up->lsr_saved_flags &= ~UART_LSR_BI;
  56                 port->serial_in(port, UART_RX);
  57                 uart_port_unlock_irqrestore(&up->port, flags);
  58                 return 1;
  59         }
  60
  61         lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
  62
  63         /* Process incoming characters first */
  64         if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
  65             (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
  66                 lsr = serial8250_rx_chars(up, lsr);
  67         }
  68
  69         /* Stop processing interrupts on input overrun */
  70         if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
  71                 unsigned long delay;
  72
  73                 up->ier = port->serial_in(port, UART_IER);
  74                 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
  75                         port->ops->stop_rx(port);
  76                 } else {
  77                         /* Keep restarting the timer until
  78                          * the input overrun subsides.
  79                          */
  80                         cancel_delayed_work(&up->overrun_backoff);
  81                 }
  82
  83                 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
  84                 schedule_delayed_work(&up->overrun_backoff, delay);
  85         }
  86
  87         serial8250_modem_status(up);
  88
  89         if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
  90                 serial8250_tx_chars(up);
  91
  92         up->lsr_saved_flags |= orig_lsr & UART_LSR_BI;
  93
  94         uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
  95
  96         return 1;
  97 }
  98 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
  99
 100 #ifdef CONFIG_ACPI
 101 struct fsl8250_data {
 102         int     line;
 103 };
 104
 105 static int fsl8250_acpi_probe(struct platform_device *pdev)
 106 {
 107         struct fsl8250_data *data;
 108         struct uart_8250_port port8250;
 109         struct device *dev = &pdev->dev;
 110         struct resource *regs;
 111
 112         int ret, irq;
 113
 114         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 115         if (!regs) {
 116                 dev_err(dev, "no registers defined\n");
 117                 return -EINVAL;
 118         }
 119
 120         irq = platform_get_irq(pdev, 0);
 121         if (irq < 0)
 122                 return irq;
 123
 124         memset(&port8250, 0, sizeof(port8250));
 125
 126         ret = device_property_read_u32(dev, "clock-frequency",
 127                                         &port8250.port.uartclk);
 128         if (ret)
 129                 return ret;
 130
 131         spin_lock_init(&port8250.port.lock);
 132
 133         port8250.port.mapbase           = regs->start;
 134         port8250.port.irq               = irq;
 135         port8250.port.handle_irq        = fsl8250_handle_irq;
 136         port8250.port.type              = PORT_16550A;
 137         port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
 138                                                 | UPF_FIXED_PORT | UPF_IOREMAP
 139                                                 | UPF_FIXED_TYPE;
 140         port8250.port.dev               = dev;
 141         port8250.port.mapsize           = resource_size(regs);
 142         port8250.port.iotype            = UPIO_MEM;
 143         port8250.port.irqflags          = IRQF_SHARED;
 144
 145         port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
 146                                                         port8250.port.mapsize);
 147         if (!port8250.port.membase)
 148                 return -ENOMEM;
 149
 150         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 151         if (!data)
 152                 return -ENOMEM;
 153
 154         data->line = serial8250_register_8250_port(&port8250);
 155         if (data->line < 0)
 156                 return data->line;
 157
 158         platform_set_drvdata(pdev, data);
 159         return 0;
 160 }
 161
 162 static int fsl8250_acpi_remove(struct platform_device *pdev)
 163 {
 164         struct fsl8250_data *data = platform_get_drvdata(pdev);
 165
 166         serial8250_unregister_port(data->line);
 167         return 0;
 168 }
 169
 170 static const struct acpi_device_id fsl_8250_acpi_id[] = {
 171         { "NXP0018", 0 },
 172         { },
 173 };
 174 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
 175
 176 static struct platform_driver fsl8250_platform_driver = {
 177         .driver = {
 178                 .name                   = "fsl-16550-uart",
 179                 .acpi_match_table       = ACPI_PTR(fsl_8250_acpi_id),
 180         },
 181         .probe                  = fsl8250_acpi_probe,
 182         .remove                 = fsl8250_acpi_remove,
 183 };
 184
 185 module_platform_driver(fsl8250_platform_driver);
 186 #endif
 187
 188 MODULE_LICENSE("GPL");
 189 MODULE_DESCRIPTION("Handling of Freescale specific 8250 variants");