serial: 8250: Add CAP_MINI, set for bcm2835aux

The AUX/mini-UART in the BCM2835 family of procesors is a cut-down
8250 clone. In particular it is lacking support for the following
features: CSTOPB PARENB PARODD CMSPAR CS5 CS6

Add a new capability (UART_CAP_MINI) that exposes the restrictions to
the user of the termios API by turning off the unsupported features in
the request.

N.B. It is almost possible to automatically discover the missing
features by reading back the LCR register, but the CSIZE bits don't
cooperate (contrary to the documentation, both bits are significant,
but CS5 and CS6 are mapped to CS7) and the code is much longer.

See: https://github.com/raspberrypi/linux/issues/1561

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index 0c23b0079a51977275a16a3c3849dc70f6cb7267..5258a82e73758ec156781b601407eb1840657999 100644 (file)
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -81,6 +81,9 @@ struct serial8250_config {
 #define UART_CAP_HFIFO (1 << 14)       /* UART has a "hidden" FIFO */
 #define UART_CAP_RPM   (1 << 15)       /* Runtime PM is active while idle */
 #define UART_CAP_IRDA  (1 << 16)       /* UART supports IrDA line discipline */
+#define UART_CAP_MINI  (1 << 17)       /* Mini UART on BCM283X family lacks:
+                                        * STOP PARITY EPAR SPAR WLEN5 WLEN6
+                                        */
 
 #define UART_BUG_QUOT  (1 << 0)        /* UART has buggy quot LSB */
 #define UART_BUG_TXEN  (1 << 1)        /* UART has buggy TX IIR status */

diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
index e10f1244409b344b850ffbbd4af5757a66c875f1..a23c7da42ea81342efc26fb35a92a69d535b7cd0 100644 (file)
--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
@@ -39,7 +39,7 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
 
        /* initialize data */
        spin_lock_init(&data->uart.port.lock);
-       data->uart.capabilities = UART_CAP_FIFO;
+       data->uart.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
        data->uart.port.dev = &pdev->dev;
        data->uart.port.regshift = 2;
        data->uart.port.type = PORT_16550;

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index f6e4373a88504b2684dfe86b4c929eb57e47a41f..a44a529e21c123aff2051b4b73d1fac34e511201 100644 (file)
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2557,6 +2557,12 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
        unsigned long flags;
        unsigned int baud, quot, frac = 0;
 
+       if (up->capabilities & UART_CAP_MINI) {
+               termios->c_cflag &= ~(CSTOPB | PARENB | PARODD | CMSPAR);
+               if ((termios->c_cflag & CSIZE) == CS5 ||
+                   (termios->c_cflag & CSIZE) == CS6)
+                       termios->c_cflag = (termios->c_cflag & ~CSIZE) | CS7;
+       }
        cval = serial8250_compute_lcr(up, termios->c_cflag);
 
        baud = serial8250_get_baud_rate(port, termios, old);