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

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Hi Anurag,

Anurag Kumar Vulisha wrote:
> Gadget applications may have a requirement to disable the U1 and U2
> entry based on the usecase. For example, when performing performance
> benchmarking on mass storage gadget the U1 and U2 entries can be disabled.
> Another example is 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 (since ping is issued from host for every uframe interval). In this
> case the U1 and U2 entry can be disabled. This 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
> commands to the gadget. Thus entry of U1 and U2 states can be avioded.
> This patch updates the same

I don't think we should assume that's the case for every host driver.

>
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xxxxxxxxxx>
> ---
>  drivers/usb/dwc3/core.c   |  4 ++++
>  drivers/usb/dwc3/core.h   |  4 ++++
>  drivers/usb/dwc3/gadget.c | 19 +++++++++++++++++++
>  drivers/usb/dwc3/gadget.h |  6 ++++++
>  4 files changed, 33 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index a1b126f..4f0912c 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");

Please use "-" rather than "_" in the property names.

>  	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/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;
> +	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;
> +}
> +
>  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))

Setting the exit latency for U1/U2 to 0 to prevent U1/U2 entry looks
more like a workaround than actually disabling U1/U2. There are
DCTL.INITU1/2ENA and DCTL.ACCEPTU1/2ENA for that.

Also, if these properties are set, then the device should rejects
SET_FEATURE(U1/U2) requests.

You can review Felipe's little code snippet from here to disable U1/U2:
https://marc.info/?l=linux-usb&m=155419284426942&w=2

BR,
Thinh




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