| Message ID | 20201218164234.128762-1-jckuo@nvidia.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xhci: tegra: Delay for disabling LFPS detector | expand |
On Sat, Dec 19, 2020 at 12:42:34AM +0800, JC Kuo wrote: > Occasionally, we are seeing some SuperSpeed devices resumes right after > being directed to U3. This commits add 500us delay to ensure LFPS > detector is disabled before sending ACK to firmware. > > [ 16.099363] tegra-xusb 70090000.usb: entering ELPG > [ 16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203 > [ 16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16 > [ 16.120789] tegra-xusb 70090000.usb: entering ELPG failed > > Signed-off-by: JC Kuo <jckuo@nvidia.com> > --- > drivers/usb/host/xhci-tegra.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c > index 934be1686352..20cdc11f7dc6 100644 > --- a/drivers/usb/host/xhci-tegra.c > +++ b/drivers/usb/host/xhci-tegra.c > @@ -623,6 +623,12 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra, > enable); > if (err < 0) > break; > + > + /* > + * wait 500us for LFPS detector to be disabled before sending ACK > + */ > + if (!enable) > + usleep_range(500, 1000); Where does the magic 500us come from? How can we "know" this is long enough? thanks, greg k-h
On 12/19/20 12:53 AM, Greg KH wrote: > On Sat, Dec 19, 2020 at 12:42:34AM +0800, JC Kuo wrote: >> Occasionally, we are seeing some SuperSpeed devices resumes right after >> being directed to U3. This commits add 500us delay to ensure LFPS >> detector is disabled before sending ACK to firmware. >> >> [ 16.099363] tegra-xusb 70090000.usb: entering ELPG >> [ 16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203 >> [ 16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16 >> [ 16.120789] tegra-xusb 70090000.usb: entering ELPG failed >> >> Signed-off-by: JC Kuo <jckuo@nvidia.com> >> --- >> drivers/usb/host/xhci-tegra.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c >> index 934be1686352..20cdc11f7dc6 100644 >> --- a/drivers/usb/host/xhci-tegra.c >> +++ b/drivers/usb/host/xhci-tegra.c >> @@ -623,6 +623,12 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra, >> enable); >> if (err < 0) >> break; >> + >> + /* >> + * wait 500us for LFPS detector to be disabled before sending ACK >> + */ >> + if (!enable) >> + usleep_range(500, 1000); > > Where does the magic 500us come from? How can we "know" this is long > enough? Hi Greg, The register write passes through a few flop stages of 32KHz clock domain. Our ASIC designer reviewed RTL and suggests 500us delay. It has also been verified thoroughly. Thanks, JC > > thanks, > > greg k-h >
On 6.1.2021 8.05, JC Kuo wrote: > On 12/19/20 12:53 AM, Greg KH wrote: >> On Sat, Dec 19, 2020 at 12:42:34AM +0800, JC Kuo wrote: >>> Occasionally, we are seeing some SuperSpeed devices resumes right after >>> being directed to U3. This commits add 500us delay to ensure LFPS >>> detector is disabled before sending ACK to firmware. >>> >>> [ 16.099363] tegra-xusb 70090000.usb: entering ELPG >>> [ 16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203 >>> [ 16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16 >>> [ 16.120789] tegra-xusb 70090000.usb: entering ELPG failed >>> >>> Signed-off-by: JC Kuo <jckuo@nvidia.com> >>> --- >>> drivers/usb/host/xhci-tegra.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c >>> index 934be1686352..20cdc11f7dc6 100644 >>> --- a/drivers/usb/host/xhci-tegra.c >>> +++ b/drivers/usb/host/xhci-tegra.c >>> @@ -623,6 +623,12 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra, >>> enable); >>> if (err < 0) >>> break; >>> + >>> + /* >>> + * wait 500us for LFPS detector to be disabled before sending ACK >>> + */ >>> + if (!enable) >>> + usleep_range(500, 1000); >> >> Where does the magic 500us come from? How can we "know" this is long >> enough? > > Hi Greg, > The register write passes through a few flop stages of 32KHz clock domain. Our > ASIC designer reviewed RTL and suggests 500us delay. It has also been verified > thoroughly. > Could you add that comment to the commit message? I can pick it up then. Should this go to stable as well? Thanks -Mathias
On 1/7/21 5:53 PM, Mathias Nyman wrote: > On 6.1.2021 8.05, JC Kuo wrote: >> On 12/19/20 12:53 AM, Greg KH wrote: >>> On Sat, Dec 19, 2020 at 12:42:34AM +0800, JC Kuo wrote: >>>> Occasionally, we are seeing some SuperSpeed devices resumes right after >>>> being directed to U3. This commits add 500us delay to ensure LFPS >>>> detector is disabled before sending ACK to firmware. >>>> >>>> [ 16.099363] tegra-xusb 70090000.usb: entering ELPG >>>> [ 16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203 >>>> [ 16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16 >>>> [ 16.120789] tegra-xusb 70090000.usb: entering ELPG failed >>>> >>>> Signed-off-by: JC Kuo <jckuo@nvidia.com> >>>> --- >>>> drivers/usb/host/xhci-tegra.c | 6 ++++++ >>>> 1 file changed, 6 insertions(+) >>>> >>>> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c >>>> index 934be1686352..20cdc11f7dc6 100644 >>>> --- a/drivers/usb/host/xhci-tegra.c >>>> +++ b/drivers/usb/host/xhci-tegra.c >>>> @@ -623,6 +623,12 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra, >>>> enable); >>>> if (err < 0) >>>> break; >>>> + >>>> + /* >>>> + * wait 500us for LFPS detector to be disabled before sending ACK >>>> + */ >>>> + if (!enable) >>>> + usleep_range(500, 1000); >>> >>> Where does the magic 500us come from? How can we "know" this is long >>> enough? >> >> Hi Greg, >> The register write passes through a few flop stages of 32KHz clock domain. Our >> ASIC designer reviewed RTL and suggests 500us delay. It has also been verified >> thoroughly. >> > > Could you add that comment to the commit message? I can pick it up then. > Should this go to stable as well? > Hi Mathias, Yes, I will send v2 with the information in commit message. Yes, this should go to stable as well. Thanks, JC > Thanks > -Mathias >
diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c index 934be1686352..20cdc11f7dc6 100644 --- a/drivers/usb/host/xhci-tegra.c +++ b/drivers/usb/host/xhci-tegra.c @@ -623,6 +623,12 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra, enable); if (err < 0) break; + + /* + * wait 500us for LFPS detector to be disabled before sending ACK + */ + if (!enable) + usleep_range(500, 1000); } if (err < 0) {
Occasionally, we are seeing some SuperSpeed devices resumes right after being directed to U3. This commits add 500us delay to ensure LFPS detector is disabled before sending ACK to firmware. [ 16.099363] tegra-xusb 70090000.usb: entering ELPG [ 16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203 [ 16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16 [ 16.120789] tegra-xusb 70090000.usb: entering ELPG failed Signed-off-by: JC Kuo <jckuo@nvidia.com> --- drivers/usb/host/xhci-tegra.c | 6 ++++++ 1 file changed, 6 insertions(+)