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

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Message-ID: <ebe0b4dd-0603-4ef5-8007-d0a768561e95@kernel.org>
Date: Wed, 9 Oct 2024 14:50:22 +0300
From: Roger Quadros <rogerq@...nel.org>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <len.brown@...el.com>,
 Pavel Machek <pavel@....cz>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Nishanth Menon <nm@...com>,
 Tero Kristo <kristo@...nel.org>, Santosh Shilimkar <ssantosh@...nel.org>,
 Dhruva Gole <d-gole@...com>, Vishal Mahaveer <vishalm@...com>,
 "msp@...libre.com" <msp@...libre.com>, "srk@...com" <srk@...com>,
 "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
 "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: core: Fix system suspend on TI AM62 platforms



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@...r.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@...nel.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:
>>
>> 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