linux-kernel - Re: [RFC 1/8] serial:st-asc: Add ST ASC driver.

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Message-ID: <518A9330.2010906@st.com>
Date:	Wed, 08 May 2013 19:02:24 +0100
From:	Srinivas KANDAGATLA <srinivas.kandagatla@...com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	gregkh@...uxfoundation.org, jslaby@...e.cz,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Stuart Menefy <stuart.menefy@...com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Olof Johansson <olof@...om.net>,
	Jason Cooper <jason@...edaemon.net>,
	Stephen Warren <swarren@...dia.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Nicolas Pitre <nico@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Dave Martin <dave.martin@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Dong Aisheng <dong.aisheng@...aro.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux-serial@...r.kernel.org,
	Stephen Gallimore <stephen.gallimore@...com>
Subject: Re: [RFC 1/8] serial:st-asc: Add ST ASC driver.

Thankyou for the comments.
On 08/05/13 15:34, Arnd Bergmann wrote:
> On Wednesday 08 May 2013, Srinivas KANDAGATLA wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla@...com>
>> +*st-asc(Serial Port)
>> +
>> +Required properties:
>> +- compatible : Should be "st,asc".
> Are there any hardware revision numbers for the asc? If there are potentially
> incompatible or backwards-compatible variants, it would be good to include
> the version in this string.
Unfortunately, there is no version numbering for this IP.
>
>> +- reg, reg-names, interrupts, interrupt-names	: Standard way to define device
>> +			resources with names. look in
>> +			Documentation/devicetree/bindings/resource-names.txt
>> +
>> +Optional properties:
>> +- st,hw-flow-ctrl	bool flag to enable hardware flow control.
>> +- st,force-m1		bool flat to force asc to be in Mode-1 recommeded
>> +			for high bit rates (above 19.2K)
>> +Example:
>> +serial@...40000{
>> +    compatible    = "st,asc";
>> +    reg         = <0xfe440000 0x2c>;
>> +    interrupts     =  <0 209 0>;
>> +};
> I would also recommed adding a way to set the default baud rate through
> a property. Following the example of the 8250 driver, you should probably
> call that "current-speed".
Yes, I will add this in the next version.
>
>> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
>> index 7e7006f..346f325 100644
>> --- a/drivers/tty/serial/Kconfig
>> +++ b/drivers/tty/serial/Kconfig
>> @@ -1484,6 +1484,25 @@ config SERIAL_RP2_NR_UARTS
>>  	  If multiple cards are present, the default limit of 32 ports may
>>  	  need to be increased.
>>  
>> +config SERIAL_ST_ASC
>> +	tristate "ST ASC serial port support"
>> +	depends on PLAT_STIXXXX
>> +	default y
>> +	select SERIAL_CORE
>> +	help
>> +	  This driver is for the on-chip Asychronous Serial Controller on
>> +	  STMicroelectronics STixxxx SoCs.
>> +	  ASC is embedded in ST COMMS IP block. It supports Rx & Tx functionality.
>> +	  It support all industry standard baud rates.
>> +
>> +	  If unsure, say N.
> I would not make it "default y".
Yep.
>> +config SERIAL_ST_ASC_CONSOLE
>> +	bool "Support for console on ST ASC"
>> +	depends on SERIAL_ST_ASC
>> +	default y
>> +	select SERIAL_CORE_CONSOLE
>> +
>>  endmenu
> This needs to be "depends on SERIAL_ST_ASC=y". You would get a link error
> if you try to make SERIAL_ST_ASC a loadable module and SERIAL_ST_ASC_CONSOLE
> built-in.
Ok, got it.
>
>> +
>> +static struct asc_port asc_ports[ASC_MAX_PORTS];
>> +static struct uart_driver asc_uart_driver;
>> +
>> +/*---- Forward function declarations---------------------------*/
>> +static irqreturn_t asc_interrupt(int irq, void *ptr);
>> +static void asc_transmit_chars(struct uart_port *);
>> +static int asc_set_baud(struct asc_port *ascport, int baud);
>> +
> Please remove all forward declarations, by reordering the functions in
> the way they are called.
Will do.
>
>
>> diff --git a/drivers/tty/serial/st-asc.h b/drivers/tty/serial/st-asc.h
>> new file mode 100644
>> index 0000000..e59f818
>> --- /dev/null
>> +++ b/drivers/tty/serial/st-asc.h
>> +#ifndef _ST_ASC_H
>> +#define _ST_ASC_H
>> +
>> +#include <linux/serial_core.h>
>> +#include <linux/clk.h>
>> +
>> +struct asc_port {
>> +	struct uart_port port;
>> +	struct clk *clk;
>> +	unsigned int hw_flow_control:1;
>> +	unsigned int check_parity:1;
>> +	unsigned int force_m1:1;
>> +};
> Since this header file is only used in one place, just merge it into
> the driver itself.
Ok, will do it.

>
>> +#define ASC_MAJOR		204
>> +#define ASC_MINOR_START		40
> I don't know what the current policy is on allocating major/minor numbers,
> but I'm sure you cannot just reuse one that is already used.
>
> Documentation/devices.txt lists the ones that are officially assigned.
> Can't you use dynamic allocation here?
>
> 	Arnd
>

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