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

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Message-ID: <CA+H2tpH2dKFHxHUaGtr-vEqxZDtQ_MVTmQTnu5kn-zzUFyXk4Q@mail.gmail.com>
Date:	Mon, 20 Oct 2014 18:23:38 +0800
From:	Orson Zhai <orsonzhai@...il.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	Chunyan Zhang <chunyan.zhang@...eadtrum.com>,
	Catalin Marinas <catalin.marinas@....com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"jslaby@...e.cz" <jslaby@...e.cz>,
	Kumar Gala <galak@...eaurora.org>,
	Mark Brown <broonie@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	"m-karicheri2@...com" <m-karicheri2@...com>,
	Pawel Moll <pawel.moll@....com>,
	Ramkumar Ramachandra <artagnon@...il.com>,
	"rrichter@...ium.com" <rrichter@...ium.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Will Deacon <will.deacon@....com>,
	Geng Ren (任赓) <geng.ren@...eadtrum.com>,
	Zhizhou Zhang (张治洲) 
	<zhizhou.zhang@...eadtrum.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	sprdlinux <sprdlinux@...elists.org>
Subject: Re: [PATCH v2 5/5] tty/serial: Add earlycon support for Spreadtrum
 serial driver

On Sun, Oct 19, 2014 at 5:06 AM, One Thousand Gnomes
<gnomes@...rguk.ukuu.org.uk> wrote:
> 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
>

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
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