> >+Pawel & Peter > >On 09/05/2023 08:58, Ravi Gunasekaran wrote: >> Hi Roger, >> >> On 05/05/23 6:02 pm, Roger Quadros wrote: >>> Hi Ravi, >>> >>> On 05/05/2023 15:13, Ravi Gunasekaran wrote: >>>> From: Aswath Govindraju <a-govindr...@ti.com> >>>> >>>> When the device port is in a low power state [U3/L2/Not Connected], >>>> accesses to usb device registers may take a long time. This could >>>> lead to potential core hang when the controller registers are >>>> accessed after the port is disabled by setting DEVDS field. Setting >>>> the fast register access bit ensures that the PHY clock is keeping up in >active state. >>>> >>>> Therefore, set fast access bit to ensure the accesses to device >>>> registers are quick even in low power states. >>>> >>>> Signed-off-by: Aswath Govindraju <a-govindr...@ti.com> >>>> --- >>>> drivers/usb/cdns3/gadget.c | 4 ++++ >>>> 1 file changed, 4 insertions(+) >>>> >>>> diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c >>>> index fcaeab9cc1..fddc8c931a 100644 >>>> --- a/drivers/usb/cdns3/gadget.c >>>> +++ b/drivers/usb/cdns3/gadget.c >>>> @@ -2321,6 +2321,9 @@ static void cdns3_gadget_config(struct >cdns3_device *priv_dev) >>>> writel(USB_IEN_INIT, ®s->usb_ien); >>>> writel(USB_CONF_CLK2OFFDS | USB_CONF_L1DS, ®s->usb_conf); >>>> >>>> + /* Set the Fast access bit */ >>>> + writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr); >>>> + >>> >>> Should this be done in cdns3_gadget_udc_start() so it is symmetric? >>> >> >> cdns3_gadget_config() is called in cdns3_gadget_udc_start() and >> cdns3_gadget_resume(). These settings seems to be needed during resume >> as well. > >But this bit was never cleared in suspend so why do you need to set it again it >in resume? >
In my opinion setting PUSB_PWR_FST_REG_ACCESS is not needed in cdns3_gadget_resume, but it should not have any negative impact for driver. The cdns3_gadget_config function seems like a good place for setting this bit. Regards, Pawel Laszczak >The commit log says that this bit must be kept set in low power states. > >> >>>> cdns3_configure_dmult(priv_dev, NULL); >>>> >>>> cdns3_gadget_pullup(&priv_dev->gadget, 1); @@ -2378,6 +2381,7 >@@ >>>> static int cdns3_gadget_udc_stop(struct usb_gadget *gadget) >>>> >>>> /* disable interrupt for device */ >>>> writel(0, &priv_dev->regs->usb_ien); >>>> + writel(0, &priv_dev->regs->usb_pwr); >>>> writel(USB_CONF_DEVDS, &priv_dev->regs->usb_conf); >>>> >>>> return ret; >>>> >>>> base-commit: a25dcda452bf6a6de72764a8d990d72e5def643d >>> > >-- >cheers, >-roger