RE: [PATCH] USB: dwc2: add a call to device_reset_optional()

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> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of John Crispin
> Sent: Friday, October 10, 2014 10:27 AM
> 
> We need this for dwc2 to work on older ralink SoC like the rt3052.
> 
> Signed-off-by: John Crispin <blogic@xxxxxxxxxxx>
> ---
>  drivers/usb/dwc2/hcd.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> index 4d918ed..8b5f966 100644
> --- a/drivers/usb/dwc2/hcd.c
> +++ b/drivers/usb/dwc2/hcd.c
> @@ -47,6 +47,7 @@
>  #include <linux/io.h>
>  #include <linux/slab.h>
>  #include <linux/usb.h>
> +#include <linux/reset.h>
> 
>  #include <linux/usb/hcd.h>
>  #include <linux/usb/ch11.h>
> @@ -2764,6 +2765,11 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg, int irq,
> 
>  	dev_dbg(hsotg->dev, "DWC OTG HCD INIT\n");
> 
> +	/* reset the device if a reset controller is present */
> +	retval = device_reset_optional(hsotg->dev);
> +	if (retval && retval != -ENOSYS)
> +		return retval;
> +
>  	/* Detect config values from hardware */
>  	retval = dwc2_get_hwparams(hsotg);
> 

Hmm. Can you explain this a bit more? I'm not familiar with the reset
control API.

But I see that there is currently no user of device_reset_optional() in
the kernel. Looks like drivers typically call devm_reset_control_get()
in their probe functions, then save the returned pointer and call it
later to do the reset. I wonder why dwc2 would be the only driver not
to do it that way?

-- 
Paul

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