Re: [PATCH v2 3/3] usb: dwc3: gadget: Add support for disabling U1 and U2 entries

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

Hi Anurag,

Anurag Kumar Vulisha wrote:
> Gadget applications may have a requirement to disable the U1 and U2
> entry based on the usecase. Below are few usecases where the disabling
> U1/U2 entries may be possible.
>
> Usecase 1:
> When combining dwc3 with an redriver for a USB Type-C device solution, it
> sometimes have problems with leaving U1/U2 for certain hosts, resulting in
> link training errors and reconnects. For this U1/U2 state entries may be
> avoided.
>
> Usecase 2:
> When performing performance benchmarking on mass storage gadget the
> U1 and U2 entries can be disabled.
>
> Usecase 3:
> When periodic transfers like ISOC transfers are used with bInterval
> of 1 which doesn't require the link to enter into U1 or U2 state entry
> (since ping is issued from host for every uframe interval). In this
> case the U1 and U2 entry can be disabled.
>
> Disablement of U1/U2 can be done by setting U1DevExitLat and U2DevExitLat
> values to 0 in the BOS descriptor. Host on seeing 0 value for U1DevExitLat
> and U2DevExitLat, it doesn't send SET_SEL requests to the gadget. There
> may be some hosts which may send SET_SEL requests even after seeing 0 in
> the UxDevExitLat of BOS descriptor. To aviod U1/U2 entries for these type
> of hosts, dwc3 controller can be programmed to reject those U1/U2 requests
> by not enabling ACCEPTUxENA bits in DCTL register.
>
> This patch updates the same.
>
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> Signed-off-by: Claus H. Stovgaard <cst@phaseone.com>
> ---
>  Changes in v2
> 	1. As suggested by Thinh Nguyen changed the "snps,dis_u1_entry_quirk"
> 	   to "snps,dis-u1-entry-quirk"
> 	2. Merged the changes done by Claus H. Stovgaard in ep0.c for rejecting
> 	   U1/U2 requests into this patch. Changes done by Claus can be found
> 	   here https://urldefense.proofpoint.com/v2/url?u=https-3A__marc.info_-3Fl-3Dlinux-2Dkernel-26m-3D155722068820568-26w-3D2&d=DwIBAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=u9FYoxKtyhjrGFcyixFYqTjw1ZX0VsG2d8FCmzkTY-w&m=dJMdvubLsepuGRDdkLZNJ00bhu52jPV7TZaFkDGD0Vs&s=wT7eyWpRKPAqXmLfdfiArbnZ7vE9Vi8DOfRdULmeIqY&e=
> 	3. Changed the commit message.
> ---
>  drivers/usb/dwc3/core.c   |  4 ++++
>  drivers/usb/dwc3/core.h   |  4 ++++
>  drivers/usb/dwc3/ep0.c    |  9 ++++++++-
>  drivers/usb/dwc3/gadget.c | 19 +++++++++++++++++++
>  drivers/usb/dwc3/gadget.h |  6 ++++++
>  5 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index a1b126f..180239b 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1285,6 +1285,10 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  				"snps,dis_u2_susphy_quirk");
>  	dwc->dis_enblslpm_quirk = device_property_read_bool(dev,
>  				"snps,dis_enblslpm_quirk");
> +	dwc->dis_u1_entry_quirk = device_property_read_bool(dev,
> +				"snps,dis-u1-entry-quirk");
> +	dwc->dis_u2_entry_quirk = device_property_read_bool(dev,
> +				"snps,dis-u2-entry-quirk");
>  	dwc->dis_rxdet_inp3_quirk = device_property_read_bool(dev,
>  				"snps,dis_rxdet_inp3_quirk");
>  	dwc->dis_u2_freeclk_exists_quirk = device_property_read_bool(dev,
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 1528d39..fa398e2 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1015,6 +1015,8 @@ struct dwc3_scratchpad_array {
>   * @dis_u2_susphy_quirk: set if we disable usb2 suspend phy
>   * @dis_enblslpm_quirk: set if we clear enblslpm in GUSB2PHYCFG,
>   *                      disabling the suspend signal to the PHY.
> + * @dis_u1_entry_quirk: set if link entering into U1 state needs to be disabled.
> + * @dis_u2_entry_quirk: set if link entering into U2 state needs to be disabled.
>   * @dis_rxdet_inp3_quirk: set if we disable Rx.Detect in P3
>   * @dis_u2_freeclk_exists_quirk : set if we clear u2_freeclk_exists
>   *			in GUSB2PHYCFG, specify that USB2 PHY doesn't
> @@ -1206,6 +1208,8 @@ struct dwc3 {
>  	unsigned		dis_u3_susphy_quirk:1;
>  	unsigned		dis_u2_susphy_quirk:1;
>  	unsigned		dis_enblslpm_quirk:1;
> +	unsigned		dis_u1_entry_quirk:1;
> +	unsigned		dis_u2_entry_quirk:1;
>  	unsigned		dis_rxdet_inp3_quirk:1;
>  	unsigned		dis_u2_freeclk_exists_quirk:1;
>  	unsigned		dis_del_phy_power_chg_quirk:1;
> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
> index 8efde17..8e94efc 100644
> --- a/drivers/usb/dwc3/ep0.c
> +++ b/drivers/usb/dwc3/ep0.c
> @@ -379,6 +379,8 @@ static int dwc3_ep0_handle_u1(struct dwc3 *dwc, enum usb_device_state state,
>  	if ((dwc->speed != DWC3_DSTS_SUPERSPEED) &&
>  			(dwc->speed != DWC3_DSTS_SUPERSPEED_PLUS))
>  		return -EINVAL;
> +	if (dwc->dis_u1_entry_quirk)

We only need to reject on SET_FEATURE(enable U1/U2) and not
SET_FEATURE(disable U1/U2).

Let's change the if condition to if (set && dis_u1_entry_quirk).

> +		return -EINVAL;
>  
>  	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>  	if (set)
> @@ -401,6 +403,8 @@ static int dwc3_ep0_handle_u2(struct dwc3 *dwc, enum usb_device_state state,
>  	if ((dwc->speed != DWC3_DSTS_SUPERSPEED) &&
>  			(dwc->speed != DWC3_DSTS_SUPERSPEED_PLUS))
>  		return -EINVAL;
> +	if (dwc->dis_u2_entry_quirk)

Same comment as previous.

> +		return -EINVAL;
>  
>  	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>  	if (set)
> @@ -626,7 +630,10 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
>  			 * nothing is pending from application.
>  			 */
>  			reg = dwc3_readl(dwc->regs, DWC3_DCTL);
> -			reg |= (DWC3_DCTL_ACCEPTU1ENA | DWC3_DCTL_ACCEPTU2ENA);
> +			if (!dwc->dis_u1_entry_quirk)
> +				reg |= DWC3_DCTL_ACCEPTU1ENA;
> +			if (!dwc->dis_u2_entry_quirk)
> +				reg |= DWC3_DCTL_ACCEPTU2ENA;
>  			dwc3_writel(dwc->regs, DWC3_DCTL, reg);
>  		}
>  		break;
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index e293400..f2d3112 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2073,6 +2073,24 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>  	return 0;
>  }
>  
> +static void dwc3_gadget_config_params(struct usb_gadget *g,
> +				      struct usb_dcd_config_params *params)
> +{
> +	struct dwc3		*dwc = gadget_to_dwc(g);
> +
> +	/* U1 Device exit Latency */
> +	if (dwc->dis_u1_entry_quirk)
> +		params->bU1devExitLat = 0;

It doesn't make sense to have exit latency of 0. Rejecting
SET_FEATURE(enable U1/U2) should already let the host know that the
device doesn't support U1/U2.

> +	else
> +		params->bU1devExitLat = DWC3_DEFAULT_U1_DEV_EXIT_LAT;
> +
> +	/* U2 Device exit Latency */
> +	if (dwc->dis_u2_entry_quirk)
> +		params->bU2DevExitLat = 0;
> +	else
> +		params->bU2DevExitLat = DWC3_DEFAULT_U2_DEV_EXIT_LAT;

This is a le16 value. Assign it with cpu_to_le16().

> +}
> +
>  static void dwc3_gadget_set_speed(struct usb_gadget *g,
>  				  enum usb_device_speed speed)
>  {
> @@ -2142,6 +2160,7 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
>  	.udc_start		= dwc3_gadget_start,
>  	.udc_stop		= dwc3_gadget_stop,
>  	.udc_set_speed		= dwc3_gadget_set_speed,
> +	.get_config_params	= dwc3_gadget_config_params,
>  };
>  
>  /* -------------------------------------------------------------------------- */
> diff --git a/drivers/usb/dwc3/gadget.h b/drivers/usb/dwc3/gadget.h
> index 3ed738e..5faf4d1 100644
> --- a/drivers/usb/dwc3/gadget.h
> +++ b/drivers/usb/dwc3/gadget.h
> @@ -48,6 +48,12 @@ struct dwc3;
>  /* DEPXFERCFG parameter 0 */
>  #define DWC3_DEPXFERCFG_NUM_XFER_RES(n)	((n) & 0xffff)
>  
> +/* U1 Device exit Latency */
> +#define DWC3_DEFAULT_U1_DEV_EXIT_LAT	0x0A	/* Less then 10 microsec */
> +
> +/* U2 Device exit Latency */
> +#define DWC3_DEFAULT_U2_DEV_EXIT_LAT	0x1FF	/* Less then 511 microsec */
> +
>  /* -------------------------------------------------------------------------- */
>  
>  #define to_dwc3_request(r)	(container_of(r, struct dwc3_request, request))

BR,
Thinh