On 10/22/2015 07:36 PM, Timur Tabi wrote:

On Fri, Sep 18, 2015 at 5:51 AM, Andre Przywara [off-list ref] wrote:

quoted

quoted

 static void pl011_putc(struct uart_port *port, int c)
 {
-       while (readl(port->membase + REG_FR) & UART01x_FR_TXFF)
+       struct uart_amba_port *uap =
+           container_of(port, struct uart_amba_port, port);
+
+       while (pl011_readw(uap, REG_FR) & UART01x_FR_TXFF)
                ;
-       writeb(c, port->membase + REG_DR);
-       while (readl(port->membase + REG_FR) & UART01x_FR_BUSY)
+       pl011_writeb(uap, c, REG_DR);
+       while (pl011_readw(uap, REG_FR) & UART01x_FR_BUSY)
                ;
 }

Just for the records, as this has been discussed before: pl011_putc() is
called by the earlycon code, before the uart_port is actually
initialized. So we cannot rely on the accessors, but have to use the
old-fashioned director accessors for this.

Which means you cannot use that approach to get earlycon support for the
ZTE UART, if I get this correctly. It shouldn't be to hard to introduce
another earlycon type specificly for that one, copying pl011_early_write
and pl011_early_console_setup and changing pl011_putc into
zte_uart_putc. But of course this belongs into the final patch (or a
separate one), not in this. So I guess you just leave that function
unchanged in this patch.

How about something like this?  It adds the "sbsa32" option to the
earlycon command-line parameter.

static void pl011_putc(struct uart_port *port, int c)
{
    while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF)
        cpu_relax();
    writeb(c, port->membase + UART01x_DR);
    while (readl(port->membase + UART01x_FR) & UART01x_FR_BUSY)
        cpu_relax();
}

static void pl011_early_write(struct console *con, const char *s, unsigned n)
{
    struct earlycon_device *dev = con->data;

    uart_console_write(&dev->port, s, n, pl011_putc);
}

static void pl011_putc_sbsa32(struct uart_port *port, int c)
{
    while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF)
        cpu_relax();
    writel(c, port->membase + UART01x_DR);
    while (readl(port->membase + UART01x_FR) & UART01x_FR_BUSY)
        cpu_relax();
}

static void pl011_early_write_sbsa32(struct console *con, const char
*s, unsigned n)
{
    struct earlycon_device *dev = con->data;

    uart_console_write(&dev->port, s, n, pl011_putc_sbsa32);
}

static int __init pl011_early_console_setup(struct earlycon_device *device,
                        const char *opt)
{
    if (!device->port.membase)
        return -ENODEV;

    if (strcmp(device->options, "sbsa32"))
        device->con->write = pl011_early_write_sbsa32;
    else
        device->con->write = pl011_early_write;

    return 0;
}

For earlycon support, I'd prefer to see different OF_EARLYCON_DECLARE()
(and EARLYCON_DECLARE()) declarations with alternate setup() functions
for zte and sbsa32. For example:

static int __init zte_early_console_setup(struct earlycon_device *device,
	const char *opt)
{
	if (!device->port.membase)
		return -ENODEV;
	device->con->write = zte_early_write;
	return 0;
}

static int __init sbsa32_early_console_setup(struct earlycon_device *device,
	const char *opt)
{
	if (!device->port.membase)
		return -ENODEV;
	device->con->write = sbsa32_early_write;
	return 0;
}

EARLYCON_DECLARE(zte, zte_early_console_setup);
OF_EARLYCON_DECLARE(zte, ".......", zte_early_console_setup);
EARLYCON_DECLARE(sbsa32, sbsa32_early_console_setup);
OF_EARLYCON_DECLARE(sbsa32, "arm,sbsa-uart", sbsa32_early_console_setup);

The above assumes that the sbsa32 maintains the equivalence of
earlycon and console; ie., that 

/ {
	chosen {
		stdout-path = &uart0;
	};

	soc {
		uart0: serial at xxxxxx {
			compatible = "arm,sbsa-uart";
		};
	};
};


will start a sbsa32 earlycon and later replace that with
sbsa console.


Regards,
Peter Hurley