15.06.2021 04:05, Peter Chen пишет:
> On 21-06-13 17:59:35, Dmitry Osipenko wrote:
>> Some devices need an extra delay after losing VBUS, otherwise VBUS may
>> be detected as active at suspend time, preventing the PHY's suspension
>> by the VBUS detection sensor. This problem was found on Asus Transformer
>> TF700T (Tegra30) tablet device, where the USB PHY wakes up immediately
>> from suspend because VBUS sensor continues to detect VBUS as active after
>> disconnection. We need to poll the PHY's VBUS wakeup status until it's
>> deasserted before suspending PHY in order to fix this minor trouble.
>>
>> Fixes: 35192007d28d ("usb: phy: tegra: Support waking up from a low power mode")
>> Reported-by: Maxim Schwalm <maxim.schwalm@xxxxxxxxx> # Asus TF700T
>> Tested-by: Maxim Schwalm <maxim.schwalm@xxxxxxxxx> # Asus TF700T
>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
>> ---
>> drivers/usb/phy/phy-tegra-usb.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/usb/phy/phy-tegra-usb.c b/drivers/usb/phy/phy-tegra-usb.c
>> index fc5c6cab58ba..ff482c694200 100644
>> --- a/drivers/usb/phy/phy-tegra-usb.c
>> +++ b/drivers/usb/phy/phy-tegra-usb.c
>> @@ -64,6 +64,7 @@
>> #define A_VBUS_VLD_WAKEUP_EN BIT(30)
>>
>> #define USB_PHY_VBUS_WAKEUP_ID 0x408
>> +#define VBUS_WAKEUP_STS BIT(10)
>> #define VBUS_WAKEUP_WAKEUP_EN BIT(30)
>>
>> #define USB1_LEGACY_CTRL 0x410
>> @@ -645,6 +646,15 @@ static int utmi_phy_power_off(struct tegra_usb_phy *phy)
>> void __iomem *base = phy->regs;
>> u32 val;
>>
>> + /*
>> + * Give hardware time to settle down after VBUS disconnection,
>> + * otherwise PHY will immediately wake up from suspend.
>> + */
>> + if (phy->wakeup_enabled && phy->mode != USB_DR_MODE_HOST)
>> + readl_relaxed_poll_timeout(base + USB_PHY_VBUS_WAKEUP_ID,
>> + val, !(val & VBUS_WAKEUP_STS),
>> + 5000, 100000);
>> +
>
> Where will clear VBUS_WAKEUP_STS? Or it will be cleared by HW after VBUS lower than
> B Session Valid?
It's cleared by hardware. Tegra documentation doesn't explicitly saying
what voltage level is used by the VBUS_WAKEUP sensor, but it implies the
session-valid level.
There are two sensors that could be used for detection of
cable-insertion into B-device USB port of Tegra: VBUS_WAKEUP and
A_SESS_VLD (from perspective of Tegra as a B-device).
The VBUS_WAKEUP sensor may not work in some hardware configurations,
always outputting 0. Seems it depends on whether port is OTG-capable
(VBUS_WAKEUP works) or fixed to a device mode. IIUC, only VBUS_WAKEUP
sensor can generate wake event that can resume system for a deepest
suspend state.
