linux-kernel - Re: [PATCH v2 5/5] tty/serial: Add earlycon support for Spreadtrum serial driver

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Date:	Sat, 18 Oct 2014 22:06:15 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Chunyan Zhang <chunyan.zhang@...eadtrum.com>
Cc:	<catalin.marinas@....com>, <gregkh@...uxfoundation.org>,
	<ijc+devicetree@...lion.org.uk>, <jslaby@...e.cz>,
	<galak@...eaurora.org>, <broonie@...aro.org>,
	<mark.rutland@....com>, <m-karicheri2@...com>,
	<pawel.moll@....com>, <artagnon@...il.com>, <rrichter@...ium.com>,
	<robh+dt@...nel.org>, <will.deacon@....com>, <orsonzhai@...il.com>,
	<geng.ren@...eadtrum.com>, <zhizhou.zhang@...eadtrum.com>,
	<devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <sprdlinux@...elists.org>
Subject: Re: [PATCH v2 5/5] tty/serial: Add earlycon support for Spreadtrum
 serial driver

On Fri, 17 Oct 2014 17:54:25 +0800
Chunyan Zhang <chunyan.zhang@...eadtrum.com> wrote:

> Add serial driver for spreadtrum sharkl platform with earlycon
> support at first.

> +#define UART_TXD	0x0000
> +#define UART_RXD	0x0004
> +#define UART_STS0	0x0008
> +#define UART_STS1	0x000C
> +#define UART_IEN	0x0010
> +#define UART_ICLR	0x0014
> +#define UART_CTL0	0x0018
> +#define UART_CTL1	0x001C
> +#define UART_CTL2	0x0020
> +#define UART_CLKD0	0x0024
> +#define UART_CLKD1	0x0028
> +#define UART_STS2	0x002C
> +
> +/*line status */
> +#define UART_LSR_TX_OVER	(0x1<<15)

Given we use UART_ for all the 8250 defines it might be better to use
something else - SHARK_LSR_TX_OVER etc to avoid future confusion

> +static void serial_sprd_putc(struct uart_port *port, int c)
> +{
> +	while (!(readl(port->membase + UART_STS0) & UART_LSR_TX_OVER))
> +		;
> +	writeb(c, port->membase + UART_TXD);
> +}
> +
> +static void serial_sprd_early_write(struct console *con, const char *s,
> +				    unsigned n)
> +{
> +	struct earlycon_device *dev = con->data;
> +
> +	uart_console_write(&dev->port, s, n, serial_sprd_putc);
> +}
> +
> +static int __init serial_sprd_early_console_setup(
> +				struct earlycon_device *device,
> +				const char *opt)
> +{
> +	if (!device->port.membase)
> +		return -ENODEV;
> +
> +	device->con->write = serial_sprd_early_write;
> +	return 0;
> +}

This seems fine but it would be useful to see both the earlycon and the
main uart/console driver and how they fit together.

Alan
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