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://lore.kernel.org/all/1519dbe7-73b6-4afc-bfe3-23f4f75d772f@kernel.org/
Signed-off-by: Roger Quadros <rogerq@kernel.org>
---
Changes in v2:
- Fix comment style
- Use both USB3 and USB2 SUSPHY bits to determine susphy_state during system suspend/resume.
- Restore SUSPHY bits at system resume regardless if it was set or cleared before system suspend.
- Link to v1: https://lore.kernel.org/r/20241001-am62-lpm-usb-v1-1-9916b71165f7@kernel.org
---
 drivers/usb/dwc3/core.c | 21 +++++++++++++++++++++
 drivers/usb/dwc3/core.h |  2 ++
 2 files changed, 23 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 9eb085f359ce..20209de2b295 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -2336,6 +2336,11 @@ 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) ||
+			    (dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0)) &
+			    DWC3_GUSB3PIPECTL_SUSPHY);
+
 	switch (dwc->current_dr_role) {
 	case DWC3_GCTL_PRTCAP_DEVICE:
 		if (pm_runtime_suspended(dwc->dev))
@@ -2387,6 +2392,15 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
 		break;
 	}
 
+	if (!PMSG_IS_AUTO(msg)) {
+		/*
+		 * TI AM62 platform requires SUSPHY to be
+		 * enabled for system suspend to work.
+		 */
+		if (!dwc->susphy_state)
+			dwc3_enable_susphy(dwc, true);
+	}
+
 	return 0;
 }
 
@@ -2454,6 +2468,13 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
 		break;
 	}
 
+	if (!PMSG_IS_AUTO(msg)) {
+		/*
+		 * restore SUSPHY state to that before system suspend.
+		 */
+		dwc3_enable_susphy(dwc, dwc->susphy_state);
+	}
+
 	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>

On Wed, Oct 09, 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!YzLHxyM7y0mqLoGNnBBdkQT-x-08cWwWSIMYbhJZ5W6kLZMaIemCRn4u3tHWoGIJyDrsI7TpN7g1oWKtC_vI$ 
> Signed-off-by: Roger Quadros <rogerq@kernel.org>
> ---
> Changes in v2:
> - Fix comment style
> - Use both USB3 and USB2 SUSPHY bits to determine susphy_state during system suspend/resume.
> - Restore SUSPHY bits at system resume regardless if it was set or cleared before system suspend.
> - Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/r/20241001-am62-lpm-usb-v1-1-9916b71165f7@kernel.org__;!!A4F2R9G_pg!YzLHxyM7y0mqLoGNnBBdkQT-x-08cWwWSIMYbhJZ5W6kLZMaIemCRn4u3tHWoGIJyDrsI7TpN7g1ocSA1YLs$ 
> ---
>  drivers/usb/dwc3/core.c | 21 +++++++++++++++++++++
>  drivers/usb/dwc3/core.h |  2 ++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 9eb085f359ce..20209de2b295 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -2336,6 +2336,11 @@ 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) ||
> +			    (dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0)) &
> +			    DWC3_GUSB3PIPECTL_SUSPHY);
> +
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
>  		if (pm_runtime_suspended(dwc->dev))
> @@ -2387,6 +2392,15 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  		break;
>  	}
>  
> +	if (!PMSG_IS_AUTO(msg)) {
> +		/*
> +		 * TI AM62 platform requires SUSPHY to be
> +		 * enabled for system suspend to work.
> +		 */
> +		if (!dwc->susphy_state)
> +			dwc3_enable_susphy(dwc, true);
> +	}
> +
>  	return 0;
>  }
>  
> @@ -2454,6 +2468,13 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  		break;
>  	}
>  
> +	if (!PMSG_IS_AUTO(msg)) {
> +		/*
> +		 * restore SUSPHY state to that before system suspend.
> +		 */

Very minor nit: use this style for single line comment:

/* single line comment */

> +		dwc3_enable_susphy(dwc, dwc->susphy_state);
> +	}
> +
>  	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.

Can you update this description now that we check for
DWC3_GUSB3PIPECTL_SUSPHY also?

>   * @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>
> 

The rest looks good to me!
You can add this Ack after the couple minor fixes:

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

Thanks,
Thinh