linux-kernel - Re: [PATCH v3] USB: dummy-hcd: fix power budget for SuperSpeed mode

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Date:   Thu, 5 Sep 2019 10:14:28 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Jacky.Cao@...y.com
cc:     balbi@...nel.org, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <Kento.A.Kobayashi@...y.com>
Subject: Re: [PATCH v3] USB: dummy-hcd: fix power budget for SuperSpeed mode

On Thu, 5 Sep 2019 Jacky.Cao@...y.com wrote:

> The power budget for SuperSpeed mode should be 900 mA
> according to USB specification, so set the power budget
> to 900mA for dummy_start_ss which is only used for
> SuperSpeed mode.
> 
> If the max power consumption of SuperSpeed device is
> larger than 500 mA, insufficient available bus power
> error happens in usb_choose_configuration function
> when the device connects to dummy hcd.
> 
> Signed-off-by: Jacky Cao <Jacky.Cao@...y.com>
> ---
> Changes in v3:
>   - Rename POWER_BUDGET_3_0 to POWER_BUDGET_3
>   - Update commit message from USB3.0 specification to USB specification
> 
> Changes in v2:
>   - Fix whitespace damage
> 
>  drivers/usb/gadget/udc/dummy_hcd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> index 8414fac..3d499d9 100644
> --- a/drivers/usb/gadget/udc/dummy_hcd.c
> +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> @@ -48,6 +48,7 @@
>  #define DRIVER_VERSION	"02 May 2005"
>  
>  #define POWER_BUDGET	500	/* in mA; use 8 for low-power port testing */
> +#define POWER_BUDGET_3	900	/* in mA */
>  
>  static const char	driver_name[] = "dummy_hcd";
>  static const char	driver_desc[] = "USB Host+Gadget Emulator";
> @@ -2432,7 +2433,7 @@ static int dummy_start_ss(struct dummy_hcd *dum_hcd)
>  	dum_hcd->rh_state = DUMMY_RH_RUNNING;
>  	dum_hcd->stream_en_ep = 0;
>  	INIT_LIST_HEAD(&dum_hcd->urbp_list);
> -	dummy_hcd_to_hcd(dum_hcd)->power_budget = POWER_BUDGET;
> +	dummy_hcd_to_hcd(dum_hcd)->power_budget = POWER_BUDGET_3;
>  	dummy_hcd_to_hcd(dum_hcd)->state = HC_STATE_RUNNING;
>  	dummy_hcd_to_hcd(dum_hcd)->uses_new_polling = 1;
>  #ifdef CONFIG_USB_OTG

Acked-by: Alan Stern <stern@...land.harvard.edu>