serial: 8250_ni16550: Add support for NIC7A69

This device uses a 33.333MHz clock with a prescaler value of 1.125 to
achieve baud rates within 1% error up to 921600 baud. We query ACPI
standard _DSD properties to determine if each port is an RS-232 or RS-485
port.

Signed-off-by: Kyle Roeschley <[email protected]>
Natinst-ReviewBoard-ID: 286745

drivers/acpi/acpi_pnp.c

@@ -224,6 +224,7 @@ static const struct acpi_device_id acpi_pnp_device_ids[] = {
  {"NIC7750"}, /* National Instruments (NI) 16550 PNP */
  {"NIC7772"}, /* National Instruments (NI) 16550 PNP */
  {"NIC792B"}, /* National Instruments (NI) 16550 PNP */
+ {"NIC7A69"}, /* National Instruments (NI) 16550 PNP */
  {"PMC2430"}, /* Pace 56 Voice Internal Plug & Play Modem */
  {"PNP0500"}, /* Generic standard PC COM port */
  {"PNP0501"}, /* Generic 16550A-compatible COM port */

drivers/tty/serial/8250/8250_pnp.c

@@ -24,6 +24,7 @@
 #include "8250.h"
 
 #include <linux/ni16550.h>
+#include <linux/property.h>
 
 #define UNKNOWN_DEV 0x3000
 #define CIR_PORT 0x0800
@@ -32,6 +33,7 @@
 #define NI_CAP_PMR 0x0001
 #define NI_CLK_33333333 0x0002
 #define NI_CPR_CLK_25000000 0x0008
+#define NI_CPR_CLK_33333333 0x0010
 
 static bool is_niport(struct pnp_dev *dev)
 {
@@ -219,6 +221,7 @@ static const struct pnp_device_id pnp_dev_table[] = {
  { "NIC7750", NI_CLK_33333333 },
  { "NIC7772", NI_CAP_PMR | NI_16BYTE_FIFO },
  { "NIC792B", NI_CPR_CLK_25000000 },
+ { "NIC7A69", NI_CPR_CLK_33333333 },
  /* NEC 98NOTE SPEAKER PHONE FAX MODEM(33600bps) */
  { "nEC8241", 0 },
  /* Pace 56 Voice Internal Plug & Play Modem */
@@ -502,10 +505,15 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
 
 #ifdef CONFIG_SERIAL_8250_NI16550
  if (is_niport(dev)) {
- WARN_ON((flags & (NI_CLK_33333333 | NI_CPR_CLK_25000000)) ==
- (NI_CLK_33333333 | NI_CPR_CLK_25000000));
+ bool rs232_property = false;
+
+ WARN_ON(hweight32(flags & (NI_CPR_CLK_25000000 |
+ NI_CPR_CLK_33333333 |
+ NI_CLK_33333333)) > 1);
+
  if (flags & NI_CLK_33333333)
  uart.port.uartclk = 33333333;
+
  if (flags & NI_CPR_CLK_25000000) {
  /* Sets UART clock rate to 22.222 MHz
  * with prescaler 1.125.
@@ -515,6 +523,27 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
  ni16550_config_prescaler(uart.port.iobase, 0x9);
  }
 
+ if (flags & NI_CPR_CLK_33333333) {
+ const char *transceiver;
+
+ /*
+ * Set UART clock rate to 29.629 MHz
+ * with prescaler 1.125.
+ */
+ uart.port.uartclk = 29629629;
+ uart.mcr_force = UART_MCR_CLKSEL;
+ ni16550_config_prescaler(uart.port.iobase, 0x9);
+
+ if (device_property_read_string(&dev->dev,
+ "transceiver",
+ &transceiver)) {
+ dev_err(&dev->dev, "transceiver property missing\n");
+ return -EINVAL;
+ }
+
+ rs232_property = strncmp(transceiver, "RS-232", 6) == 0;
+ }
+
  uart.port.flags |= UPF_FIXED_PORT | UPF_FIXED_TYPE;
 
  if (flags & NI_16BYTE_FIFO)
@@ -523,18 +552,21 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
  uart.port.type = PORT_NI16550_F128;
 
  /*
- * NI UARTs are by default connected to RS-485 transceivers,
- * unless the PMR register is implemented, and the UART is
- * dual-mode capable. Then it could be in RS-232 mode and if it
- * is, we will register as a standard 8250 port.
+ * NI UARTs may be connected to RS-485 or RS-232 transceivers,
+ * depending on the ACPI 'transceiver' property and whether or
+ * not the PMR is implemented. If the PMR is implemented and
+ * the port is in RS-232 mode, register as a standard 8250 port
+ * and print about it.
  */
  if ((flags & NI_CAP_PMR) && is_rs232_mode(uart.port.iobase))
  pr_info("NI 16550 at I/O 0x%x (irq = %d) is dual-mode capable and is in RS-232 mode\n",
  (unsigned int)uart.port.iobase,
  uart.port.irq);
- else
- /* Either the PMR register is not implemented, or it is
- * and the UART is in RS-485 mode as set in the PMR
+ else if (!rs232_property)
+ /*
+ * Either the PMR is implemented and set to RS-485 mode
+ * or it's not implemented and the 'transceiver' ACPI
+ * property is 'RS-485';
  */
  ni16550_port_setup(&uart.port);
  }