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SubjectRe: [PATCH] U6715 16550A serial driver support
On Mon, 2 Aug 2010 10:58:39 +0200
Philippe Langlais <philippe.langlais@stericsson.com> wrote:

> UART Features extract from STEricsson U6715 data-sheet (arm926 SoC for mobile phone):
> * Fully compatible with industry standard 16C550 and 16C450 from various
> manufacturers
> * RX and TX 64 byte FIFO reduces CPU interrupts
> * Full double buffering
> * Modem control signals include CTS, RTS, (and DSR, DTR on UART1 only)
> * Automatic baud rate selection
> * Manual or automatic RTS/CTS smart hardware flow control
> * Programmable serial characteristics:
> ___ Baud rate generation (50 to 3.25M baud)
> ___ 5, 6, 7 or 8-bit characters
> ___ Even, odd or no-parity bit generation and detection
> ___ 1, 1.5 or 2 stop bit generation
> * Independent control of transmit, receive, line status, data set interrupts and FIFOs
> * Full status-reporting capabilities
> * Separate DMA signaling for RX and TX
> * Timed interrupt to spread receive interrupt on known duration
> * DMA time-out interrupt to allow detection of end of reception
> * Carkit pulse coding and decoding compliant with USB carkit control interface [40]
>
> In 16550A auto-configuration, if the fifo size is 64 then it's an U6 16550A port
> Add set_termios hook & export serial8250_do_set_termios to change uart
> clock following baudrate

Confused.

> ...
>
> --- a/include/linux/serial_8250.h
> +++ b/include/linux/serial_8250.h
> @@ -32,6 +32,9 @@ struct plat_serial8250_port {
> unsigned int type; /* If UPF_FIXED_TYPE */
> unsigned int (*serial_in)(struct uart_port *, int);
> void (*serial_out)(struct uart_port *, int, int);
> + void (*set_termios)(struct uart_port *,
> + struct ktermios *new,
> + struct ktermios *old);
> };
>
> ...
>
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -279,6 +279,9 @@ struct uart_port {
> unsigned char __iomem *membase; /* read/write[bwl] */
> unsigned int (*serial_in)(struct uart_port *, int);
> void (*serial_out)(struct uart_port *, int, int);
> + void (*set_termios)(struct uart_port *,
> + struct ktermios *new,
> + struct ktermios *old);
> unsigned int irq; /* irq number */
> unsigned long irqflags; /* irq flags */
> unsigned int uartclk; /* base uart clock */

The patch adds these .set_termios hooks but doesn't actually use them
for anything.

The changelog doesn't tell us _why_ this was done (it should) and
lacking any code to look at it's all a bit mysterious.



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