linux-kernel - Re: [PATCH v2 01/11] serial:st-asc: Add ST ASC driver.

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Date:	Mon, 10 Jun 2013 10:35:11 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Srinivas KANDAGATLA <srinivas.kandagatla@...com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	"David S. Miller" <davem@...emloft.net>,
	devicetree-discuss@...ts.ozlabs.org,
	Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Olof Johansson <olof@...om.net>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Stephen Gallimore <stephen.gallimore@...com>,
	Stuart Menefy <stuart.menefy@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Prisk <linux@...sktech.co.nz>
Subject: Re: [PATCH v2 01/11] serial:st-asc: Add ST ASC driver.

On Mon, Jun 10, 2013 at 10:21:00AM +0100, Srinivas KANDAGATLA wrote:
> This patch adds support to ASC (asynchronous serial controller)
> driver, which is basically a standard serial driver. This IP is common
> across all the ST parts for settop box platforms.
> 
> ASC is embedded in ST COMMS IP block. It supports Rx & Tx functionality.
> It support all industry standard baud rates.

Your driver is not POSIX compliant.

> +		for (; count != 0; count--) {
> +			c = asc_in(port, ASC_RXBUF);
> +			flag = TTY_NORMAL;
> +			port->icount.rx++;
> +
> +			if (unlikely(c & ASC_RXBUF_FE)) {
> +				if (c == ASC_RXBUF_FE) {
> +					port->icount.brk++;
> +					if (uart_handle_break(port))
> +						continue;
> +					flag = TTY_BREAK;
> +				} else {
> +					port->icount.frame++;
> +					flag = TTY_FRAME;
> +				}
> +			} else if (ascport->check_parity &&
> +				   unlikely(c & ASC_RXBUF_PE)) {
> +				port->icount.parity++;
> +				flag = TTY_PARITY;
> +			}
> +
> +			if (uart_handle_sysrq_char(port, c))
> +				continue;
> +			tty_insert_flip_char(tport, c & 0xff, flag);
> +		}
> +		if (overrun) {
> +			port->icount.overrun++;
> +			tty_insert_flip_char(tport, 0, TTY_OVERRUN);
> +		}

No support for ignoring error conditions.  No support for ignoring all
input... and:

> +static void asc_set_termios(struct uart_port *port, struct ktermios *termios,
> +			    struct ktermios *old)
> +{
> +	struct asc_port *ascport = to_asc_port(port);
> +	unsigned int baud;
> +	u32 ctrl_val;
> +	tcflag_t cflag;
> +	unsigned long flags;
> +
> +	port->uartclk = clk_get_rate(ascport->clk);
> +
> +	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
> +	cflag = termios->c_cflag;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +
> +	/* read control register */
> +	ctrl_val = asc_in(port, ASC_CTL);
> +
> +	/* stop serial port and reset value */
> +	asc_out(port, ASC_CTL, (ctrl_val & ~ASC_CTL_RUN));
> +	ctrl_val = ASC_CTL_RXENABLE | ASC_CTL_FIFOENABLE;
> +
> +	/* reset fifo rx & tx */
> +	asc_out(port, ASC_TXRESET, 1);
> +	asc_out(port, ASC_RXRESET, 1);
> +
> +	/* set character length */
> +	if ((cflag & CSIZE) == CS7) {
> +		ctrl_val |= ASC_CTL_MODE_7BIT_PAR;
> +	} else {
> +		ctrl_val |= (cflag & PARENB) ?  ASC_CTL_MODE_8BIT_PAR :
> +						ASC_CTL_MODE_8BIT;
> +	}
> +
> +	ascport->check_parity = (cflag & PARENB) ? 1 : 0;
> +
> +	/* set stop bit */
> +	ctrl_val |= (cflag & CSTOPB) ? ASC_CTL_STOP_2BIT : ASC_CTL_STOP_1BIT;
> +
> +	/* odd parity */
> +	if (cflag & PARODD)
> +		ctrl_val |= ASC_CTL_PARITYODD;
> +
> +	/* hardware flow control */
> +	if ((cflag & CRTSCTS) && ascport->hw_flow_control)
> +		ctrl_val |= ASC_CTL_CTSENABLE;

This doesn't reflect those facts back into the termios structure to
indicate that they aren't supported.

Consider using uart_port's ignore and read status masks to implement
the break, framing, parity and overrun checking in your interrupt
handler using the same methodology as drivers like 8250, amba-pl011
etc.  That will help you get these code sequences correct.
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