linux-kernel - Re: [PATCH v2] serial: 8250

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Date:   Mon, 29 May 2017 11:43:22 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Joel Stanley <joel@....id.au>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] serial: 8250_of: Add reset support

Hi Joel,

On Fri, 2017-05-26 at 11:55 +1000, Joel Stanley wrote:
> This adds the hooks for an optional reset controller in the 8250 device
> tree node.
> 
> Signed-off-by: Joel Stanley <joel@....id.au>
> 
> ---
> v2:
>  Address Philipp's comments. Thanks for the review!
>  - use _shared variant
>  - remove unnecessary error handling
> 
>  Documentation/devicetree/bindings/serial/8250.txt |  1 +
>  drivers/tty/serial/8250/8250_of.c                 | 10 ++++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
> index 10276a46ecef..63e32393f82b 100644
> --- a/Documentation/devicetree/bindings/serial/8250.txt
> +++ b/Documentation/devicetree/bindings/serial/8250.txt
> @@ -45,6 +45,7 @@ Optional properties:
>    property.
>  - tx-threshold: Specify the TX FIFO low water indication for parts with
>    programmable TX FIFO thresholds.
> +- resets : phandle + reset specifier pairs
>  
>  Note:
>  * fsl,ns16550:
> diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
> index 1cbadafc6889..e95cc9698c32 100644
> --- a/drivers/tty/serial/8250/8250_of.c
> +++ b/drivers/tty/serial/8250/8250_of.c
> @@ -19,11 +19,13 @@
>  #include <linux/of_irq.h>
>  #include <linux/of_platform.h>
>  #include <linux/clk.h>
> +#include <linux/reset.h>
>  
>  #include "8250.h"
>  
>  struct of_serial_info {
>  	struct clk *clk;
> +	struct reset_control *rst;
>  	int type;
>  	int line;
>  };
> @@ -132,6 +134,13 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
>  		}
>  	}
>  
> +	info->rst = devm_reset_control_get_optional_shared(&ofdev->dev, NULL);
> +	if (IS_ERR(info->rst))
> +		goto out;
> +	ret = reset_control_deassert(info->rst);
> +	if (ret)
> +		goto out;
> +
>  	port->type = type;
>  	port->uartclk = clk;
>  	port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP
> @@ -231,6 +240,7 @@ static int of_platform_serial_remove(struct platform_device *ofdev)
>  
>  	if (info->clk)
>  		clk_disable_unprepare(info->clk);
> +	reset_control_assert(info->rst);

The clock is enabled before the reset is deasserted in
of_platform_serial_setup, I'd disable it after asserting the reset in
of_platform_serial_remove. Other than that,

Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp