Re: [PATCH v4] tty: serial: add Freescale lpuart driver support

[Shawn Guo <shawn.guo@linaro.org>]

Jingchang,

On Tue, May 28, 2013 at 05:26:01PM +0800, Jingchang Lu wrote:
> +static void lpuart_setup_watermark(struct lpuart_port *sport)
> +{
> +	unsigned char val, old_cr2, cr2;
> +
> +	/* set receiver/transmitter trigger level. */
> +	old_cr2 = cr2 = readb(sport->port.membase + UARTCR2);
> +	cr2 &= ~(UARTCR2_TIE | UARTCR2_TCIE | UARTCR2_TE |
> +			UARTCR2_RIE | UARTCR2_RE);
> +	writeb(cr2, sport->port.membase + UARTCR2);
> +
> +	writeb(2, sport->port.membase + UARTTWFIFO);
> +	writeb(1, sport->port.membase + UARTRWFIFO);
> +
> +	/* determine FIFO size and enable */
> +	val = readb(sport->port.membase + UARTPFIFO);
> +
> +	sport->tx_fifo_size = 0x1 << (((val >> UARTPFIFO_TXSIZE_OFF) &
> +		UARTPFIFO_FIFOSIZE_MASK) + 1);
> +
> +	sport->rx_fifo_size = 0x1 << (((val >> UARTPFIFO_RXSIZE_OFF) &
> +		UARTPFIFO_FIFOSIZE_MASK) + 1);
> +
> +	writeb(val | UARTPFIFO_TXFE | UARTPFIFO_RXFE,
> +			sport->port.membase + UARTPFIFO);
> +
> +	/* Flush the Tx and Rx FIFO to a known state */
> +	writeb(UARTCFIFO_TXFLUSH | UARTCFIFO_RXFLUSH,
> +			sport->port.membase + UARTCFIFO);
> +
> +	/* restore CR2 */
> +	writeb(old_cr2, sport->port.membase + UARTCR2);

I just noticed that you dropped this CR2 restore since v5 of the patch.
I have a patch enabling low-level debug support for Vybrid.  It works
with v4 of your patch but has problem with the v5.  The console stops
working as below.

Serial: IMX driver
serial: Freescale lpuart driver
40028000.serial: ttyLP1 at MMIO 0x40028000 (irq = 94) is a FSL_LPUART
console [ttyLP1] enabled, bootconsole disabled

If I have above CR2 restore code added back.  The low-level debug
support will just work fine with console.

Is it an accident you removed the code?

Shawn

> +
> +}