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

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Message-ID: <20131017141346.GA22104@kroah.com>
Date:	Thu, 17 Oct 2013 07:13:46 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Nicolas Ferre <nicolas.ferre@...el.com>
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 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...

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

thanks,

greg k-h
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