linux-kernel - Re: [PATCH 1/3] usb: musb: da8xx: Call earlier clk_prepare

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Date:   Tue, 25 Oct 2016 14:09:20 -0500
From:   David Lechner <david@...hnology.com>
To:     Alexandre Bailon <abailon@...libre.com>, khilman@...libre.com,
        b-liu@...com, balbi@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 1/3] usb: musb: da8xx: Call earlier clk_prepare_enable()

On 10/25/2016 08:52 AM, Alexandre Bailon wrote:
> The first attempt to read a register may fail because the clock may not
> be enabled, and then the probe of musb driver will fail.
> Call clk_prepare_enable() before the first register read.
>
> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> ---
>  drivers/usb/musb/da8xx.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/musb/da8xx.c b/drivers/usb/musb/da8xx.c
> index 210b7e4..ec93602 100644
> --- a/drivers/usb/musb/da8xx.c
> +++ b/drivers/usb/musb/da8xx.c
> @@ -366,6 +366,12 @@ static int da8xx_musb_init(struct musb *musb)
>
>  	musb->mregs += DA8XX_MENTOR_CORE_OFFSET;
>
> +	ret = clk_prepare_enable(glue->clk);
> +	if (ret) {
> +		dev_err(glue->dev, "failed to enable clock\n");
> +		goto fail;

You can simply return ret; here instead of goto fail;

> +	}
> +
>  	/* Returns zero if e.g. not clocked */
>  	rev = musb_readl(reg_base, DA8XX_USB_REVISION_REG);
>  	if (!rev)
> @@ -377,12 +383,6 @@ static int da8xx_musb_init(struct musb *musb)
>  		goto fail;

The unwinding on error needs to be updated so that 
clk_disable_unprepare() is called at this point and subsequently. 
Currently, all goto fail; will return without disabling the clock.

>  	}
>
> -	ret = clk_prepare_enable(glue->clk);
> -	if (ret) {
> -		dev_err(glue->dev, "failed to enable clock\n");
> -		goto fail;
> -	}
> -
>  	setup_timer(&otg_workaround, otg_timer, (unsigned long)musb);
>
>  	/* Reset the controller */
>