Re: [PATCH 3/3] max3100: adds console support for MAX3100

[Feng Tang <feng.tang@intel.com>]

On Fri, 19 Mar 2010 16:39:57 +0800
Christian Pellegrin <chripell@fsfe.org> wrote:

> +#ifdef CONFIG_SERIAL_MAX3100_CONSOLE
> +
> +static void max3100_console_putchar(struct uart_port *port, int ch)
> +{
> +	struct max3100_port *s = container_of(port, struct
> max3100_port, port);
> +	unsigned long tout = 10 * HZ / 1000; /* 10ms */
> +	unsigned long start;
> +	u16 tx, rx;
> +
> +	if (tout == 0)
> +		tout = 1;
> +	start = jiffies;
> +	do {
> +		tx = MAX3100_RC;
> +		max3100_sr(s, tx, &rx);

Hi Christian,

You'd better not call max3110_sr (which calls spi_sync) here, a console's
putchar() func may be called in some atomic context.

I used similar method when I started to implement a console, but then I switch
to current method in my 3110 driver: save the printk buffer inside putchar,
and wake up a thread to really handle the spi transfer later.

Thanks,
Feng
> +	} while ((rx & MAX3100_T) == 0 &&
> +		 !time_after(jiffies, start + tout));
> +	tx = ch;
> +	max3100_calc_parity(s, &tx);
> +	tx |= MAX3100_WD | MAX3100_RTS;
> +	max3100_sr(s, tx, &rx);
> +}
> +
> +static void max3100_console_write(struct console *co,
> +				  const char *str, unsigned int
> count) +{
> +	struct max3100_port *s = max3100s[co->index];;
> +
> +	uart_console_write(&s->port, str, count,
> max3100_console_putchar); +}