[PATCH v2 5/5] tty/serial: Add earlycon support for Spreadtrum serial driver

Orson Zhai
2014-10-20T10:23:38Z

On Sun, Oct 19, 2014 at 5:06 AM, One Thousand Gnomes
<gnomes@lxorguk.ukuu.org.uk> wrote:
> On Fri, 17 Oct 2014 17:54:25 +0800
> Chunyan Zhang <chunyan.zhang@spreadtrum.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
>

Does it matter if those macro are only used in the specific c file?
>From my point of view, private register macro could be treated as
static definitions like static variable or functions in C file.
I also noted that many people use a prefix for the other
manufacturers' macro definition in source file .
I have no intention to break the habit of kernel but just for discussion.

>> +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