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

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Message-ID: <52600336.4050401@atmel.com>
Date:	Thu, 17 Oct 2013 17:33:10 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	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 17/10/2013 16:13, Greg Kroah-Hartman :
> On Thu, Oct 17, 2013 at 10:16:47AM +0200, Nicolas Ferre wrote:
>> On 16/10/2013 22:14, Greg Kroah-Hartman :
>>> On Tue, Oct 15, 2013 at 11:19:18AM +0200, Nicolas Ferre wrote:
>>>> 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)?
>>>
>>> Is this really a regression from 3.11?
>>
>> Yes it is. Commit id that I am referring to in patch 1/2
>> (055560b04a8cd063aea916fd083b7aec02c2adb8) hit the mainline in 3.12-rc
>> time-frame.
>
> Ok.
>
>>> What's the worry about waiting
>>> for 3.13-rc1, getting this correct, and then backporting them to the
>>> 3.12-stable trees?
>>
>> It will break all older at91 in 3.12-final. Moreover, I do think that
>> the actual patches are bringing an incorrect solution and I do not plan
>> to have a better one (which one?) for 3.13...
>>
>>> I'd prefer that, so, please clean this up properly and resend it, with
>>> the tested-by: lines and I'll queue them up for 3.13-rc1.
>>
>> I do not know what to cleanup. Anyway, tell me if you want that I resend
>> the series of 2 patches with the "Tested-by" tag included.
>
> I thought there was some dev_warn() changes that were asked for...

Asked for, but I do not agree (my arguments above).

> Anyway, please resend them if you want me to take them for any tree as I
> no longer have them in my queue.

Okay, I re-send you them right now.

Thanks, bye,
-- 
Nicolas Ferre
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