linux-kernel - Re: [PATCH] tty: serial: msm

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Date:	Mon, 10 Nov 2014 17:56:03 -0800
From:	Frank Rowand <frowand.list@...il.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	Kevin Hilman <khilman@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-serial@...r.kernel.org, Olof Johansson <olof@...om.net>,
	Arnd Bergmann <arnd@...db.de>,
	Tyler Baker <tyler.baker@...aro.org>
Subject: Re: [PATCH] tty: serial: msm_serial: Use DT aliases

On 11/10/2014 11:42 AM, Stephen Boyd wrote:
> On 11/10/2014 10:54 AM, Kevin Hilman wrote:
>> On Wed, Oct 22, 2014 at 5:33 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
>>> We rely on probe order of this driver to determine the line number for
>>> the uart port. This makes it impossible to know the line number
>>> when these devices are populated via DT. Use the DT alias
>>> mechanism to assign the line based on the aliases node.
>>>
>>> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
>> FYI... this patch hit linux-next and caused multiple boot failures on
>> qcom platforms[1] as of next-20141110.  I'm assuming this is because
>> the corresponding DTS changes have not hit linux-next yet.
>>
>> Kevin
>>
>> [1] http://status.armcloud.us/boot/?qcom
> 
> Hmm the intention was to make it optional so that dts changes aren't
> necessary unless you want deterministic numbering. I screwed that up
> badly :/ Thanks for finding this.
> 
> Greg, can you also apply this patch or squash it into the bad one?
> 
> ----8<-----
> 
> From: Stephen Boyd <sboyd@...eaurora.org>
> Subject: [PATCH] tty: serial: msm_serial: Don't required DT aliases
> 
> If there isn't a DT alias then of_alias_get_id() will return
> -ENODEV. This will cause the msm_serial driver to fail probe,
> when we want to keep the previous behavior where we generated a
> dynamic line number at probe time. Restore this behavior by
> generating a dynamic id if the line number is still negative
> after checking for an alias or (in the non-DT case) looking at the
> .id field of the platform device.
> 
> Reported-by: Kevin Hilman <khilman@...nel.org>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>  drivers/tty/serial/msm_serial.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
> index 09364dd8cf3a..d1bc6b6cbc70 100644
> --- a/drivers/tty/serial/msm_serial.c
> +++ b/drivers/tty/serial/msm_serial.c
> @@ -1046,14 +1046,14 @@ static int msm_serial_probe(struct platform_device *pdev)
>  	const struct of_device_id *id;
>  	int irq, line;
>  
> -	if (pdev->id == -1)
> -		pdev->id = atomic_inc_return(&msm_uart_next_id) - 1;
> -
>  	if (pdev->dev.of_node)
>  		line = of_alias_get_id(pdev->dev.of_node, "serial");
>  	else
>  		line = pdev->id;
>  
> +	if (line < 0)
> +		line = atomic_inc_return(&msm_uart_next_id) - 1;
> +
>  	if (unlikely(line < 0 || line >= UART_NR))

Then this original check for "line < 0" can also be removed.


>  		return -ENXIO;
>  
> 

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