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((iir & UART_IIR_ID) == UART_IIR_RLSI &&
  55                      (up->lsr_saved_flags & UART_LSR_BI))) {
  56                 up->lsr_saved_flags &= ~UART_LSR_BI;
  57                 port->serial_in(port, UART_RX);
  58                 uart_port_unlock_irqrestore(&up->port, flags);
  59                 return 1;
  60         }
  61
  62         lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
  63
  64         /* Process incoming characters first */
  65         if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
  66             (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
  67                 lsr = serial8250_rx_chars(up, lsr);
  68         }
  69
  70         /* Stop processing interrupts on input overrun */
  71         if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
  72                 unsigned long delay;
  73
  74                 up->ier = port->serial_in(port, UART_IER);
  75                 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
  76                         port->ops->stop_rx(port);
  77                 } else {
  78                         /* Keep restarting the timer until
  79                          * the input overrun subsides.
  80                          */
  81                         cancel_delayed_work(&up->overrun_backoff);
  82                 }
  83
  84                 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
  85                 schedule_delayed_work(&up->overrun_backoff, delay);
  86         }
  87
  88         serial8250_modem_status(up);
  89
  90         if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
  91                 serial8250_tx_chars(up);
  92
  93         up->lsr_saved_flags |= orig_lsr & UART_LSR_BI;
  94
  95         uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
  96
  97         return 1;
  98 }
  99 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
 100
 101 #ifdef CONFIG_ACPI
 102 struct fsl8250_data {
 103         int     line;
 104 };
 105
 106 static int fsl8250_acpi_probe(struct platform_device *pdev)
 107 {
 108         struct fsl8250_data *data;
 109         struct uart_8250_port port8250;
 110         struct device *dev = &pdev->dev;
 111         struct resource *regs;
 112
 113         int ret, irq;
 114
 115         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 116         if (!regs) {
 117                 dev_err(dev, "no registers defined\n");
 118                 return -EINVAL;
 119         }
 120
 121         irq = platform_get_irq(pdev, 0);
 122         if (irq < 0)
 123                 return irq;
 124
 125         memset(&port8250, 0, sizeof(port8250));
 126
 127         ret = device_property_read_u32(dev, "clock-frequency",
 128                                         &port8250.port.uartclk);
 129         if (ret)
 130                 return ret;
 131
 132         spin_lock_init(&port8250.port.lock);
 133
 134         port8250.port.mapbase           = regs->start;
 135         port8250.port.irq               = irq;
 136         port8250.port.handle_irq        = fsl8250_handle_irq;
 137         port8250.port.type              = PORT_16550A;
 138         port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
 139                                                 | UPF_FIXED_PORT | UPF_IOREMAP
 140                                                 | UPF_FIXED_TYPE;
 141         port8250.port.dev               = dev;
 142         port8250.port.mapsize           = resource_size(regs);
 143         port8250.port.iotype            = UPIO_MEM;
 144         port8250.port.irqflags          = IRQF_SHARED;
 145
 146         port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
 147                                                         port8250.port.mapsize);
 148         if (!port8250.port.membase)
 149                 return -ENOMEM;
 150
 151         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 152         if (!data)
 153                 return -ENOMEM;
 154
 155         data->line = serial8250_register_8250_port(&port8250);
 156         if (data->line < 0)
 157                 return data->line;
 158
 159         platform_set_drvdata(pdev, data);
 160         return 0;
 161 }
 162
 163 static void fsl8250_acpi_remove(struct platform_device *pdev)
 164 {
 165         struct fsl8250_data *data = platform_get_drvdata(pdev);
 166
 167         serial8250_unregister_port(data->line);
 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_new             = 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");