linux-kernel - Re: [PATCH 2/2] tty/serial: at91: add a fallback option to determine uart/usart property

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Date:	Tue, 15 Oct 2013 11:19:18 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
CC:	Josh Wu <josh.wu@...el.com>, Bo Shen <voice.shen@...el.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-serial@...r.kernel.org>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] tty/serial: at91: add a fallback option to determine
 uart/usart property

On 14/10/2013 15:59, Jean-Christophe PLAGNIOL-VILLARD :
> On 10:43 Thu 10 Oct     , Nicolas Ferre wrote:
>> On older SoC, the "name" field is not filled in the register map.
>> Fix the way to figure out if the serial port is an uart or an usart for these
>> older products (with corresponding properties).
>>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
>> ---
>>   drivers/tty/serial/atmel_serial.c | 19 ++++++++++++++++++-
>>   include/linux/atmel_serial.h      |  1 +
>>   2 files changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
>> index 6b0f75e..c7d99af 100644
>> --- a/drivers/tty/serial/atmel_serial.c
>> +++ b/drivers/tty/serial/atmel_serial.c
>> @@ -99,6 +99,7 @@ static void atmel_stop_rx(struct uart_port *port);
>>   #define UART_PUT_RTOR(port,v)	__raw_writel(v, (port)->membase + ATMEL_US_RTOR)
>>   #define UART_PUT_TTGR(port, v)	__raw_writel(v, (port)->membase + ATMEL_US_TTGR)
>>   #define UART_GET_IP_NAME(port)	__raw_readl((port)->membase + ATMEL_US_NAME)
>> +#define UART_GET_IP_VERSION(port) __raw_readl((port)->membase + ATMEL_US_VERSION)
>>
>>    /* PDC registers */
>>   #define UART_PUT_PTCR(port,v)	__raw_writel(v, (port)->membase + ATMEL_PDC_PTCR)
>> @@ -1503,6 +1504,7 @@ static void atmel_get_ip_name(struct uart_port *port)
>>   {
>>   	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>>   	int name = UART_GET_IP_NAME(port);
>> +	u32 version;
>>   	int usart, uart;
>>   	/* usart and uart ascii */
>>   	usart = 0x55534152;
>> @@ -1517,7 +1519,22 @@ static void atmel_get_ip_name(struct uart_port *port)
>>   		dev_dbg(port->dev, "This is uart\n");
>>   		atmel_port->is_usart = false;
>>   	} else {
>> -		dev_err(port->dev, "Not supported ip name, set to uart\n");
>> +		/* fallback for older SoCs: use version field */
>> +		version = UART_GET_IP_VERSION(port);
>> +		switch (version) {
>> +		case 0x302:
>> +		case 0x10213:
>> +			dev_dbg(port->dev, "This version is usart\n");
>> +			atmel_port->is_usart = true;
>> +			break;
>> +		case 0x203:
>> +		case 0x10202:
>> +			dev_dbg(port->dev, "This version is uart\n");
>> +			atmel_port->is_usart = false;
>> +			break;
>> +		default:
>> +			dev_err(port->dev, "Not supported ip name nor version, set to uart\n");
>
> it's not really an error a dev_warn is more oppropriate

As we are already in -rc5 and that these fixes are critical for at91 
platforms, I will not re-spin another patch just for this.

Moreover, I have the feeling that if we end up in this case, it means 
that we are in big troubles because the usart/uart included in the 
product triggering this log is not known (I recall that newer products 
do not have to hit these lines of code).

With these 2 reasons, I prefer to keep my patch like it is.

Greg, can you consider taking these two patches as regression fixes for 
3.12 (with Tested-by tag from Thomas)?

Thanks, bye,

>> +		}
>>   	}
>>   }
>>
>> diff --git a/include/linux/atmel_serial.h b/include/linux/atmel_serial.h
>> index be201ca..00beddf 100644
>> --- a/include/linux/atmel_serial.h
>> +++ b/include/linux/atmel_serial.h
>> @@ -125,5 +125,6 @@
>>   #define ATMEL_US_IF		0x4c			/* IrDA Filter Register */
>>
>>   #define ATMEL_US_NAME		0xf0			/* Ip Name */
>> +#define ATMEL_US_VERSION	0xfc			/* Ip Version */
>>
>>   #endif
>> --
>> 1.8.2.2
>>
>
>


-- 
Nicolas Ferre
--
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