Re: [PATCH] U6715 16550A serial driver support

[Philippe Langlais]

On 08/04/10 21:52, Andrew Morton wrote:
> On Mon, 2 Aug 2010 10:58:39 +0200
> Philippe Langlais<philippe.langlais@xxxxxxxxxxxxxx>  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.
>
>    
This feature is used in our U6715 8250 platform serial driver, to avoid
hack in 8250.c set_termios (Alan Cox requirement).
In this driver the input uart clock frequency depends on baud rate and
is computed in our set_termios override function.
The U6715 paltform serial patch has been submitted on linux-arm mailing 
list,
and is ready to enter Russell King Linux tree.

More things to do ?

Philippe
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