linux-kernel - Re: [PATCH] serial/arc-uart: Add new driver

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Date:	Thu, 25 Oct 2012 11:36:19 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Vineet.Gupta1@...opsys.com
Cc:	alan@...ux.intel.com, arc-linux-dev@...opsys.com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial/arc-uart: Add new driver

On Thu, Oct 25, 2012 at 12:00:08PM +0530, Vineet.Gupta1@...opsys.com wrote:
> From: Vineet Gupta <vgupta@...opsys.com>
> 
> Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
> FPGA Boards such as ARCAngel4/ML50x
> 
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> ---
>  drivers/tty/serial/Kconfig       |   25 ++
>  drivers/tty/serial/Makefile      |    1 +
>  drivers/tty/serial/arc_uart.c    |  747 ++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/serial_core.h |    2 +
>  4 files changed, 775 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/tty/serial/arc_uart.c
> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 2a53be5..efee7fe 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1423,4 +1423,29 @@ config SERIAL_EFM32_UART_CONSOLE
>  	depends on SERIAL_EFM32_UART=y
>  	select SERIAL_CORE_CONSOLE
>  
> +config SERIAL_ARC
> +	bool "ARC UART driver support"
> +	select SERIAL_CORE
> +	default y
> +	help
> +	  Driver for on-chip UART for ARC(Synopsys) for the legacy
> +	  FPGA Boards (ML50x/ARCAngel4)

Unless you will break a user's box, NEVER define a default value for a
new configuration option as y.

And why can't I select this driver as a module?

> +
> +config SERIAL_ARC_CONSOLE
> +	bool
> +	select SERIAL_CORE_CONSOLE
> +	depends on SERIAL_ARC=y
> +	default y
> +	help
> +	  Enable system Console on ARC UART
> +
> +config SERIAL_ARC_NR_PORTS
> +	int 'Number of ports'
> +	range 1 3
> +	default 1
> +	depends on SERIAL_ARC
> +	help
> +	  Set this to the number of serial ports you want the driver
> +	  to support.
> +
>  endmenu
> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> index 4f694da..df1b998 100644
> --- a/drivers/tty/serial/Makefile
> +++ b/drivers/tty/serial/Makefile
> @@ -82,3 +82,4 @@ obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
>  obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
>  obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
>  obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
> +obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
> diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
> new file mode 100644
> index 0000000..9215bf4
> --- /dev/null
> +++ b/drivers/tty/serial/arc_uart.c
> @@ -0,0 +1,747 @@
> +/*
> + * ARC On-Chip(fpga) UART Driver
> + *
> + * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * vineetg: July 10th 2012
> + *  -Decoupled the driver from arch/arc
> + *    +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
> + *    +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
> + *
> + * Vineetg: Aug 21st 2010
> + *  -Is uart_tx_stopped() not done in tty write path as it has already been
> + *   taken care of, in serial core
> + *
> + * Vineetg: Aug 18th 2010
> + *  -New Serial Core based ARC UART driver
> + *  -Derived largely from blackfin driver albiet with some major tweaks
> + *
> + * TODO:
> + *  -check if sysreq works
> + */
> +
> +#if defined(CONFIG_SERIAL_ARC_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
> +#define SUPPORT_SYSRQ
> +#endif

Are you sure this works?  Don't you usually need to include some .h
files before you check these config values?

> +
> +#include <linux/module.h>
> +#include <linux/serial.h>
> +#include <linux/console.h>
> +#include <linux/sysrq.h>
> +#include <linux/platform_device.h>
> +#include <linux/tty.h>
> +#include <linux/tty_flip.h>
> +#include <linux/serial_core.h>
> +#include <linux/io.h>
> +
> +/*************************************
> + * ARC UART Hardware Specs
> + ************************************/
> +#define ARC_UART_TX_FIFO_SIZE  1
> +
> +/*
> + * UART Register set (this is not a Standards Compliant IP)
> + * Also each reg is Word aligned, but only 8 bits wide
> + */
> +#define R_ID0	0
> +#define R_ID1	1
> +#define R_ID2	2
> +#define R_ID3	3
> +#define R_DATA	4
> +#define R_STS	5
> +#define R_BAUDL	6
> +#define R_BAUDH	7
> +
> +/* Bits for UART Status Reg (R/W) */
> +#define RXIENB  0x04	/* Receive Interrupt Enable */
> +#define TXIENB  0x40	/* Transmit Interrupt Enable */
> +
> +#define RXEMPTY 0x20	/* Receive FIFO Empty: No char receivede */
> +#define TXEMPTY 0x80	/* Transmit FIFO Empty, thus char can be written into */
> +
> +#define RXFULL  0x08	/* Receive FIFO full */
> +#define RXFULL1 0x10	/* Receive FIFO has space for 1 char (tot space=4) */
> +
> +#define RXFERR  0x01	/* Frame Error: Stop Bit not detected */
> +#define RXOERR  0x02	/* OverFlow Err: Char recv but RXFULL still set */
> +
> +/* Uart bit fiddling helpers: lowest level */
> +#define RBASE(uart, reg)      ((unsigned int *)uart->port.membase + reg)
> +#define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
> +#define UART_REG_GET(u, r)    readb(RBASE(u, r))

What happens when you run sparse on this driver?

thanks,

greg k-h
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