Re: [PATCH] usb: dwc3: core: Fix system suspend on TI AM62 platforms

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

Hi,

On Mon, Oct 07, 2024, Roger Quadros wrote:
> Hi,
> 
> On 05/10/2024 04:04, Thinh Nguyen wrote:
> > Hi,
> > 
> > On Tue, Oct 01, 2024, Roger Quadros wrote:
> >> Since commit 6d735722063a ("usb: dwc3: core: Prevent phy suspend during init"),
> >> system suspend is broken on AM62 TI platforms.
> >>
> >> Before that commit, both DWC3_GUSB3PIPECTL_SUSPHY and DWC3_GUSB2PHYCFG_SUSPHY
> >> bits (hence forth called 2 SUSPHY bits) were being set during core
> >> initialization and even during core re-initialization after a system
> >> suspend/resume.
> >>
> >> These bits are required to be set for system suspend/resume to work correctly
> >> on AM62 platforms.
> >>
> >> Since that commit, the 2 SUSPHY bits are not set for DEVICE/OTG mode if gadget
> >> driver is not loaded and started.
> >> For Host mode, the 2 SUSPHY bits are set before the first system suspend but
> >> get cleared at system resume during core re-init and are never set again.
> >>
> >> This patch resovles these two issues by ensuring the 2 SUSPHY bits are set
> >> before system suspend and restored to the original state during system resume.
> >>
> >> Cc: stable@vger.kernel.org # v6.9+
> >> Fixes: 6d735722063a ("usb: dwc3: core: Prevent phy suspend during init")
> >> Link: https://urldefense.com/v3/__https://lore.kernel.org/all/1519dbe7-73b6-4afc-bfe3-23f4f75d772f@kernel.org/__;!!A4F2R9G_pg!ahChm4MaKd6VGYqbnM4X1_pY_jqavYDv5HvPFbmicKuhvFsBwlEFi1xO5itGuHmfjbRuUSzReJISf5-1gXpr$ 
> >> Signed-off-by: Roger Quadros <rogerq@kernel.org>
> >> ---
> >>  drivers/usb/dwc3/core.c | 16 ++++++++++++++++
> >>  drivers/usb/dwc3/core.h |  2 ++
> >>  2 files changed, 18 insertions(+)
> >>
> >> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> >> index 9eb085f359ce..1233922d4d54 100644
> >> --- a/drivers/usb/dwc3/core.c
> >> +++ b/drivers/usb/dwc3/core.c
> >> @@ -2336,6 +2336,9 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> >>  	u32 reg;
> >>  	int i;
> >>  
> >> +	dwc->susphy_state = !!(dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0)) &
> >> +			    DWC3_GUSB2PHYCFG_SUSPHY);
> >> +
> >>  	switch (dwc->current_dr_role) {
> >>  	case DWC3_GCTL_PRTCAP_DEVICE:
> >>  		if (pm_runtime_suspended(dwc->dev))
> >> @@ -2387,6 +2390,11 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> >>  		break;
> >>  	}
> >>  
> >> +	if (!PMSG_IS_AUTO(msg)) {
> >> +		if (!dwc->susphy_state)
> >> +			dwc3_enable_susphy(dwc, true);
> >> +	}
> >> +
> >>  	return 0;
> >>  }
> >>  
> >> @@ -2454,6 +2462,14 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
> >>  		break;
> >>  	}
> >>  
> >> +	if (!PMSG_IS_AUTO(msg)) {
> >> +		/* dwc3_core_init_for_resume() disables SUSPHY so just handle
> >> +		 * the enable case
> >> +		 */
> > 
> > Can we note that this is a particular behavior needed for AM62 here?
> > And can we use this comment style:
> > 
> > /*
> >  * xxxxx
> >  * xxxxx
> >  */
> 
> OK.
> 
> > 
> > 
> >> +		if (dwc->susphy_state)
> > 
> > Shouldn't we check for if (!dwc->susphy_state) and clear the susphy
> > bits?
> 
> In that case it would have already been cleared so no need to check
> and clear again.
> 
> > 
> >> +			dwc3_enable_susphy(dwc, true);
> > 
> > The dwc3_enable_susphy() set and clear both GUSB3PIPECTL_SUSPHY and
> > GUSB2PHYCFG_SUSPHY, perhaps we should split that function out so we can
> > only need to set for GUSB2PHYCFG_SUSPHY since you only track for that.
> 
> As  dwc3_enable_susphy() sets and clears both GUSB3PIPECTL_SUSPHY and
> GUSB2PHYCFG_SUSPHY together it doesn't really help to track both
> separately, but just complicates things.

Then we should check if either GUSB2PHYCFG_SUSPHY or GUSB3PIPECTL_SUSPHY
is set, then apply this.

> 
> > 
> >> +	}
> >> +
> >>  	return 0;
> >>  }
> >>  
> >> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> >> index c71240e8f7c7..b2ed5aba4c72 100644
> >> --- a/drivers/usb/dwc3/core.h
> >> +++ b/drivers/usb/dwc3/core.h
> >> @@ -1150,6 +1150,7 @@ struct dwc3_scratchpad_array {
> >>   * @sys_wakeup: set if the device may do system wakeup.
> >>   * @wakeup_configured: set if the device is configured for remote wakeup.
> >>   * @suspended: set to track suspend event due to U3/L2.
> >> + * @susphy_state: state of DWC3_GUSB2PHYCFG_SUSPHY before PM suspend.
> >>   * @imod_interval: set the interrupt moderation interval in 250ns
> >>   *			increments or 0 to disable.
> >>   * @max_cfg_eps: current max number of IN eps used across all USB configs.
> >> @@ -1382,6 +1383,7 @@ struct dwc3 {
> >>  	unsigned		sys_wakeup:1;
> >>  	unsigned		wakeup_configured:1;
> >>  	unsigned		suspended:1;
> >> +	unsigned		susphy_state:1;
> >>  
> >>  	u16			imod_interval;
> >>  
> >>
> >> ---
> >> base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
> >> change-id: 20240923-am62-lpm-usb-f420917bd707
> >>
> >> Best regards,
> >> -- 
> >> Roger Quadros <rogerq@kernel.org>
> >>
> > 
> > <rant/>
> > While reviewing your change, I see that we misuse the
> > dis_u2_susphy_quirk to make this property a conditional thing during
> > suspend and resume for certain platform. That bugs me because we can't
> > easily change it without the reported hardware to test.
> > </rant>
> 
> No it is not conditional. if dis_u2_susphy_quirk or dis_u3_susphy_quirk
> is set then we never enable the respective U2/U3 SUSPHY bit.
> 

I'm not referring to your change. I was referring to this in particular:
bcb128777af5 ("usb: dwc3: core: Suspend PHYs on runtime suspend in host mode")

BR,
Thinh