diff options
| author | Matthew Howell <matthew.howell@sealevel.com> | 2023-09-29 17:40:55 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-10-03 14:36:56 +0200 |
| commit | 687911b37e89c80c47d2f105022b678aef604136 (patch) | |
| tree | df49b145225dfaaa046b5fcf9c2eebf66862e4fd /drivers/tty/serial/8250/8250_exar.c | |
| parent | 6c756af23b3333f14876a80b85028430b243f280 (diff) | |
serial: exar: Add RS-485 support for Sealevel XR17V35X based cards
Sealevel XR17V35X based cards utilize DTR to control RS-485 Enable, but
the current implementation of 8250_exar uses RTS for the auto-RS485-Enable
mode of the XR17V35X UARTs. This patch implements DTR Auto-RS485 on
Sealevel cards.
Signed-off-by: Matthew Howell <matthew.howell@sealevel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenkoa@linux.intel.com>
Link: https://lore.kernel.org/r/4b8ad8ab6728742464c4e048fdeecb2b40522aef.camel@sealevel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/8250/8250_exar.c')
| -rw-r--r-- | drivers/tty/serial/8250/8250_exar.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c index a18fc8f01a41..6085d356ad86 100644 --- a/drivers/tty/serial/8250/8250_exar.c +++ b/drivers/tty/serial/8250/8250_exar.c @@ -77,6 +77,9 @@ #define UART_EXAR_RS485_DLY(x) ((x) << 4) +#define UART_EXAR_DLD 0x02 /* Divisor Fractional */ +#define UART_EXAR_DLD_485_POLARITY 0x80 /* RS-485 Enable Signal Polarity */ + /* * IOT2040 MPIO wiring semantics: * @@ -438,6 +441,44 @@ static int generic_rs485_config(struct uart_port *port, struct ktermios *termios return 0; } +static int sealevel_rs485_config(struct uart_port *port, struct ktermios *termios, + struct serial_rs485 *rs485) +{ + u8 __iomem *p = port->membase; + u8 old_lcr; + u8 efr; + u8 dld; + int ret; + + ret = generic_rs485_config(port, termios, rs485); + if (ret) + return ret; + + if (rs485->flags & SER_RS485_ENABLED) { + old_lcr = readb(p + UART_LCR); + + /* Set EFR[4]=1 to enable enhanced feature registers */ + efr = readb(p + UART_XR_EFR); + efr |= UART_EFR_ECB; + writeb(efr, p + UART_XR_EFR); + + /* Set MCR to use DTR as Auto-RS485 Enable signal */ + writeb(UART_MCR_OUT1, p + UART_MCR); + + /* Set LCR[7]=1 to enable access to DLD register */ + writeb(old_lcr | UART_LCR_DLAB, p + UART_LCR); + + /* Set DLD[7]=1 for inverted RS485 Enable logic */ + dld = readb(p + UART_EXAR_DLD); + dld |= UART_EXAR_DLD_485_POLARITY; + writeb(dld, p + UART_EXAR_DLD); + + writeb(old_lcr, p + UART_LCR); + } + + return 0; +} + static const struct serial_rs485 generic_rs485_supported = { .flags = SER_RS485_ENABLED, }; @@ -559,6 +600,9 @@ pci_xr17v35x_setup(struct exar8250 *priv, struct pci_dev *pcidev, port->port.rs485_config = platform->rs485_config; port->port.rs485_supported = *(platform->rs485_supported); + if (pcidev->subsystem_vendor == PCI_VENDOR_ID_SEALEVEL) + port->port.rs485_config = sealevel_rs485_config; + /* * Setup the UART clock for the devices on expansion slot to * half the clock speed of the main chip (which is 125MHz) |