Re: [PATCH 1/2] usb: chipidea: Add DT vbus-supply parsing

[Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>]

On 07/28/2014 10:23 PM, Markus Pargmann wrote:
> Add some code to parse and enable vbus supply when probing.
> 
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
>  drivers/usb/imx/chipidea-imx.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/usb/imx/chipidea-imx.c b/drivers/usb/imx/chipidea-imx.c
> index 9b6829b8f59f..a4cf4a1a5f3d 100644
> --- a/drivers/usb/imx/chipidea-imx.c
> +++ b/drivers/usb/imx/chipidea-imx.c
> @@ -15,6 +15,7 @@
>  #include <common.h>
>  #include <init.h>
>  #include <io.h>
> +#include <linux/err.h>
>  #include <of.h>
>  #include <errno.h>
>  #include <driver.h>
> @@ -23,6 +24,7 @@
>  #include <usb/chipidea-imx.h>
>  #include <usb/ulpi.h>
>  #include <usb/fsl_usb2.h>
> +#include <regulator.h>
>  
>  #define MXC_EHCI_PORTSC_MASK ((0xf << 28) | (1 << 25))
>  
> @@ -187,6 +189,16 @@ static int imx_chipidea_probe(struct device_d *dev)
>  		ret = -ENODEV;
>  	}
>  
> +	if (ci->mode == IMX_USB_MODE_HOST) {
> +		struct regulator *vbus = regulator_get(dev, "vbus");
> +		if (!IS_ERR(vbus)) {
> +			regulator_enable(vbus);
> +		} else {
> +			dev_err(dev, "Failed to get vbus regulator %ld\n", PTR_ERR(vbus));
> +			ret = PTR_ERR(vbus);
> +		}

regulator_get should return a NULL pointer if there is no regulator for
"vbus". The NULL regulator is a valid (dummy) regulator that can be used
as if there was a real one.

That basically means, you should check for an error and always use
regulator_enable otherwise:

struct regulator *vbus = regulator_get(dev, "vbus");
if (IS_ERR(vbus)) {
	dev_err(dev, "Failed to get vbus regulator %ld\n", PTR_ERR(vbus));
	return PTR_ERR(vbus);
}

regulator_enable(vbus);

But even more important: You should also check for a regulator on
peripheral/otg mode. That's the cases where you can actually break
things when you don't disable the regulator.

Sebastian

> +	}
> +
>  	return ret;
>  };
>  
> 


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