linux-kernel - Re: [PATCH v8] usb: dwc3: of-simple: Add support to get resets for the device

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Date:   Fri, 20 Oct 2017 17:10:37 +0530
From:   Manu Gautam <mgautam@...eaurora.org>
To:     Philipp Zabel <p.zabel@...gutronix.de>, linux-usb@...r.kernel.org
Cc:     Felipe Balbi <balbi@...nel.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v8] usb: dwc3: of-simple: Add support to get resets for
 the device

Hi,


On 10/19/2017 5:17 PM, Philipp Zabel wrote:
> From: Vivek Gautam <vivek.gautam@...eaurora.org>
>
> 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.
>
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> [p.zabel@...gutronix.de: switch to hidden reset control array]
> Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
> ---
> v7: Rebased onto git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git testing/next
> ---
>  drivers/usb/dwc3/dwc3-of-simple.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/dwc3/dwc3-of-simple.c b/drivers/usb/dwc3/dwc3-of-simple.c
> index e129c32780818..ceea1619f8aa3 100644
> --- a/drivers/usb/dwc3/dwc3-of-simple.c
> +++ b/drivers/usb/dwc3/dwc3-of-simple.c
> @@ -28,11 +28,13 @@
>  #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;
>  };
>  
>  static int dwc3_of_simple_clk_init(struct dwc3_of_simple *simple, int count)
> @@ -95,10 +97,21 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, simple);
>  	simple->dev = dev;
>  
> +	simple->resets = of_reset_control_array_get_optional_exclusive(np);
> +	if (IS_ERR(simple->resets)) {
> +		ret = PTR_ERR(simple->resets);
> +		dev_err(dev, "failed to get device resets, err=%d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = reset_control_deassert(simple->resets);
> +	if (ret)
> +		goto err_resetc_put;
> +

Are these reset signals asserted by default after power on?
I think correct way to handle this should be to have explicit reset_control_assert
before deassert.

>  	ret = dwc3_of_simple_clk_init(simple, of_count_phandle_with_args(np,
>  						"clocks", "#clock-cells"));
>  	if (ret)
> -		return ret;
> +		goto err_resetc_assert;

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