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

[Roger Quadros]

On 08/10/2024 23:53, Thinh Nguyen wrote:
> Hi Roger,
> 
> On Tue, Oct 08, 2024, Roger Quadros wrote:
>> Hi Thinh,
>>
>> 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@xxxxxxxxxxxxxxx # 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@xxxxxxxxxx/__;!!A4F2R9G_pg!ahChm4MaKd6VGYqbnM4X1_pY_jqavYDv5HvPFbmicKuhvFsBwlEFi1xO5itGuHmfjbRuUSzReJISf5-1gXpr$ 
>>>> Signed-off-by: Roger Quadros <rogerq@xxxxxxxxxx>
>>>> ---
>>>>  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:
>>
>> Looking at this again, this fix is not specific to AM62 but for all platforms.
>> e.g. if Host Role was already started when going to system suspend, SUSPHY bits
>> were enabled, then after system resume SUSPHY bits are cleared at dwc3_core_init_for_resume().
>>
>> Host stop/start was not called so SUSPHY bits remain cleared. So here
>> we deal with enabling SUSPHY.
>>
> 
> It's true that we have a bug where the SUSPHY bits remain disabled after
> suspend. However, the SUSPHY bits needing to be set during suspend is
> unique to AM62. Let's add this note in the dwc3_suspend_common() check.

Yes I will do that. Thanks!

-- 
cheers,
-roger