linux-kernel - Re: [PATCH 01/10] serial: mvebu-uart: initial support for Armada-3700 serial port

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Message-ID: <87r3gt4uvq.fsf@free-electrons.com>
Date:	Wed, 03 Feb 2016 17:32:41 +0100
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Jason Cooper <jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	arm@...nel.org, Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Jonathan Corbet <corbet@....net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, Hans de Goede <hdegoede@...hat.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org,
	Wilson Ding <dingwei@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>
Subject: Re: [PATCH 01/10] serial: mvebu-uart: initial support for Armada-3700 serial port

Hi Mark,
 
 On mar., févr. 02 2016, Mark Rutland <mark.rutland@....com> wrote:

> On Tue, Feb 02, 2016 at 07:07:39PM +0100, Gregory CLEMENT wrote:
>> From: Wilson Ding <dingwei@...vell.com>
>> 
>> Armada-3700's uart is a simple serial port, which doesn't
>> support. Configuring the modem control lines. The uart port has a 32
>> bytes Tx FIFO and a 64 bytes Rx FIFO
>> 
>> The uart driver implements the uart core operations. It also support the
>> system (early) console based on Armada-3700's serial port.
>> 
>> Known Issue:
>> 
>> The uart driver currently doesn't support clock programming, which means
>> the baud-rate stays with the default value configured by the bootloader
>> at boot time
>
> To ensure that the bootloader and kernel match, it's best to place the
> rate in the stdout-path property (as in
> Documentation/devicetree/bindings/chosen.txt).
>
> Presumably that is what you want?

It is done in patch 7.

>
> Is it difficutl to add clock programming?

Currently there is no clock tree support before adding it I would like
to be able to test it.

Thanks,

Gregory

>
>> 
>> [gregory.clement@...e-electrons.com: Rewrite many part which are too long
>> to enumerate]
>> 
>> Signed-off-by: Wilson Ding <dingwei@...vell.com>
>> Signed-off-by: Nadav Haklai <nadavh@...vell.com>
>> Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
>> ---
>>  .../devicetree/bindings/tty/serial/mvebu-uart.txt  |  13 +
>>  Documentation/kernel-parameters.txt                |   6 +
>>  drivers/tty/serial/Kconfig                         |  22 +
>>  drivers/tty/serial/Makefile                        |   1 +
>>  drivers/tty/serial/mvebu-uart.c                    | 649 +++++++++++++++++++++
>>  include/uapi/linux/serial_core.h                   |   3 +
>>  6 files changed, 694 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/tty/serial/mvebu-uart.txt
>>  create mode 100644 drivers/tty/serial/mvebu-uart.c
>> 
>> diff --git a/Documentation/devicetree/bindings/tty/serial/mvebu-uart.txt b/Documentation/devicetree/bindings/tty/serial/mvebu-uart.txt
>> new file mode 100644
>> index 000000000000..6087defd9f93
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/tty/serial/mvebu-uart.txt
>> @@ -0,0 +1,13 @@
>> +* Marvell UART : Non standard UART used in some of Marvell EBU SoCs (e.g., Armada-3700)
>> +
>> +Required properties:
>> +- compatible: "marvell,armada-3700-uart"
>> +- reg: offset and length of the register set for the device.
>> +- interrupts: device interrupt
>> +
>> +Example:
>> +	serial@...00 {
>> +		compatible = "marvell,armada-3700-uart";
>> +		reg = <0x12000 0x400>;
>> +		interrupts = <43>;
>> +	};
>
> There are no external clock inputs?
>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 87d40a72f6a1..198f6bd56e84 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -1058,6 +1058,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>>  			A valid base address must be provided, and the serial
>>  			port must already be setup and configured.
>>  
>> +		mvebu_uart,<addr>
>> +			Start an early, polled-mode console on an some mvebu
>> +			SoC (as the Armada-3700) serial port at the specified
>> +			address. The serial port must already be setup and
>> +			configured. Options are not yet supported.
>> +
>
> Does the the mvebu UART vary between platforms at all?
>
> Thanks,
> Mark.

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com