linux-kernel - Re: [PATCH 4/4] serial/arc-uart: switch to devicetree based probing

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Date:	Fri, 08 Feb 2013 23:01:27 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Arnd Bergmann <arnd@...db.de>, Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devicetree-discuss@...ts.ozlabs.org,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>
Subject: Re: [PATCH 4/4] serial/arc-uart: switch to devicetree based probing

On Fri, 11 Jan 2013 11:50:23 +0530, Vineet Gupta <Vineet.Gupta1@...opsys.com> wrote:
> * DT binding for arc-uart
> * With alll the bits in place we can now use DT probing.
> 
> Note that there's a bit of kludge right now because earlyprintk portion
> of driver can't use the DT infrastrcuture to get resoures/plat_data.
> This requires some infrastructre changes to of_flat_ framework
> 
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> Cc: Grant Likely <grant.likely@...retlab.ca>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: linux-serial@...r.kernel.org
> Cc: Alan Cox <alan@...ux.intel.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: devicetree-discuss@...ts.ozlabs.org
> Cc: Rob Herring <rob.herring@...xeda.com>
> Cc: Rob Landley <rob@...dley.net>
> Cc: linux-serial@...r.kernel.org
> ---
>  .../devicetree/bindings/tty/serial/arc-uart.txt    |   26 ++++++++++++
>  drivers/tty/serial/arc_uart.c                      |   43 ++++++++++++++++++-
>  2 files changed, 66 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/tty/serial/arc-uart.txt
> 
> diff --git a/Documentation/devicetree/bindings/tty/serial/arc-uart.txt b/Documentation/devicetree/bindings/tty/serial/arc-uart.txt
> new file mode 100644
> index 0000000..c3bd8f9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/tty/serial/arc-uart.txt
> @@ -0,0 +1,26 @@
> +* Synopsys ARC UART : Non standard UART used in some of the ARC FPGA boards
> +
> +Required properties:
> +- compatible		: "snps,arc-uart"
> +- reg			: offset and length of the register set for the device.
> +- interrupts		: device interrupt
> +- clock-frequency	: the input clock frequency for the UART
> +- baud			: baud rate for UART

change 'baud' to 'current-speed'. There is already precedence for this
with other serial devices.

g.

> @@ -673,8 +693,18 @@ static int __init arc_serial_probe_earlyprintk(struct platform_device *pdev)
>  static int arc_serial_probe(struct platform_device *pdev)
>  {
>  	int rc, dev_id;
> +	struct device_node *np = pdev->dev.of_node;
> +
> +	/* no device tree device */
> +	if (!np)
> +		return -ENODEV;

This breaks non-DT users. Is this what you intend? It creates a flag day
where users have to switch from non-DT to DT cold-turkey.

> +	dev_id = of_alias_get_id(np, "serial");
> +	if (dev_id < 0) {
> +		dev_err(&pdev->dev, "failed to get alias id: %d\n", dev_id);
> +		return dev_id;
> +	}

Don't fail on this. If you can't get an id then choose one dynamically.

>  
> -	dev_id = pdev->id < 0 ? 0 : pdev->id;
>  	rc = arc_uart_init_one(pdev, dev_id);
>  	if (rc)
>  		return rc;
> @@ -689,12 +719,19 @@ static int arc_serial_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +static const struct of_device_id arc_uart_dt_ids[] = {
> +	{ .compatible = "snps,arc-uart" },
> +	{ /* Sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, arc_uart_dt_ids);
> +
>  static struct platform_driver arc_platform_driver = {
>  	.probe = arc_serial_probe,
>  	.remove = arc_serial_remove,
>  	.driver = {
>  		.name = DRIVER_NAME,
>  		.owner = THIS_MODULE,
> +		.of_match_table  = arc_uart_dt_ids,
>  	 },
>  };
>  
> -- 
> 1.7.4.1
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
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