linux-kernel - Re: [PATCH 2/2] usb; dwc3: of-simple: Add support to get resets for the device

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Date:   Wed, 15 Mar 2017 11:45:27 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] usb; dwc3: of-simple: Add support to get resets for
 the device

On Wed, 2017-02-22 at 10:54 +0530, Vivek Gautam wrote:
> Add support to get a list of resets available for the device.
> These resets must be kept de-asserted until the device is
> in use.
> 
> Cc: Felipe Balbi <balbi@...nel.org>
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> ---
> 
> Based on torvald's master branch.
> 
>  drivers/usb/dwc3/dwc3-of-simple.c | 49 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/dwc3-of-simple.c b/drivers/usb/dwc3/dwc3-of-simple.c
> index fe414e7a9c78..025de7342d28 100644
> --- a/drivers/usb/dwc3/dwc3-of-simple.c
> +++ b/drivers/usb/dwc3/dwc3-of-simple.c
> @@ -29,13 +29,52 @@
>  #include <linux/of.h>
>  #include <linux/of_platform.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/reset.h>
>  
>  struct dwc3_of_simple {
>  	struct device		*dev;
>  	struct clk		**clks;
>  	int			num_clocks;
> +	struct reset_control	**resets;
> +	int			num_resets;
>  };
>  
> +static int dwc3_of_simple_reset_init(struct dwc3_of_simple *simple, int count)
> +{
> +	struct device		*dev = simple->dev;
> +	int			i;
> +
> +	simple->num_resets = count;
> +
> +	if (!count)
> +		return 0;
> +
> +	simple->resets = devm_kcalloc(dev, simple->num_resets,
> +				sizeof(struct reset_control *), GFP_KERNEL);
> +	if (!simple->resets)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < simple->num_resets; i++) {
> +		struct reset_control *reset;
> +		int ret;
> +
> +		reset = devm_reset_control_get_by_index(dev, i);

Please use devm_reset_control_get_exclusive_by_index instead. See
include/linux/reset.h for details.

> +		if (IS_ERR(reset))
> +			return PTR_ERR(reset);
> +
> +		simple->resets[i] = reset;
> +
> +		ret = reset_control_deassert(reset);
> +		if (ret) {
> +			while (--i >= 0)
> +				reset_control_assert(reset);
> +			return ret;
> +		}
> +	}
> +
> +	return 0;
> +}

This looks rather generic. Should we have a
reset_control_get/assert/deassert_array functionality at the reset API
level?

>  static int dwc3_of_simple_clk_init(struct dwc3_of_simple *simple, int count)
>  {
>  	struct device		*dev = simple->dev;
> @@ -100,6 +139,10 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	ret = dwc3_of_simple_reset_init(simple, of_reset_control_get_count(np));
> +	if (ret)
> +		return ret;
> +

Not a blocker, but it seems a bit inconsistent to count the reset
controls via the device node (of_...), but then get them via the device
(devm_reset_control_get_... instead of of_reset_control_get_...).

regards
Philipp