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

From: Anurag Kumar Vulisha
Date: Tue May 07 2019 - 05:47:28 EST

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Next in thread: Anurag Kumar Vulisha: "[PATCH 1/3] doc: dt: bindings: usb: dwc3: Update entries for disabling U1 and U2"
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Hi Thinh,

>-----Original Message-----
>From: Thinh Nguyen [mailto:Thinh.Nguyen@xxxxxxxxxxxx]
>Sent: Tuesday, May 07, 2019 12:51 AM
>To: Anurag Kumar Vulisha <anuragku@xxxxxxxxxx>; Greg Kroah-Hartman
><gregkh@xxxxxxxxxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Mark Rutland
><mark.rutland@xxxxxxx>; Felipe Balbi <balbi@xxxxxxxxxx>
>Cc: linux-usb@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-
>kernel@xxxxxxxxxxxxxxx; v.anuragkumar@xxxxxxxxx
>Subject: Re: [PATCH 3/3] usb: dwc3: gadget: Add support for disabling U1 and U2
>entries
>
>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.

I agree with you, as Claus already mentioned, observed that windows 10
issues SET_SEL commands even after UxDevExitLat are zero.

>
>>
>> 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.
>

Okay , will change this

>> 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
>

As there are some host platforms (like windows 10) which initiates U1/U2 states
even after sending zero in UxExitLat of BOS descriptor, I agree with you that the
dwc3 controller should reject the U1/U2 requests from host by configuring DCTL.
Along with DCTL changes, I think the changes required for sending zero value in
UxExitLat field reported in the BOSDescriptor are also required (there is no point
in sending non-zero exit latencies when U1/U2 state entries are disabled). So, this
patch changes should be added along with the changes reported by Claus.
Please provide your suggestion on this

Thanks,
Anurag Kumar Vulisha

Next message: syzbot: "KASAN: slab-out-of-bounds Read in page_get_anon_vma"
Previous message: Serge Semin: "Re: [PATCH v2 0/3] i2c-mux-gpio: Split plat- and dt-specific code up"
In reply to: Thinh Nguyen: "Re: [PATCH 3/3] usb: dwc3: gadget: Add support for disabling U1 and U2 entries"
Next in thread: Anurag Kumar Vulisha: "[PATCH 1/3] doc: dt: bindings: usb: dwc3: Update entries for disabling U1 and U2"
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