usb: dwc3: core: Fix system suspend on TI AM62 platforms

Since commit 6d735722 ("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: 6d735722 ("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>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Tested-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: Dhruva Gole <d-gole@ti.com>
Link: https://lore.kernel.org/r/20241011-am62-lpm-usb-v3-1-562d445625b5@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/core.c

@@ -2342,6 +2342,11 @@ 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))
@@ -2393,6 +2398,15 @@ 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;
 }
 
@@ -2460,6 +2474,11 @@ 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;
 }
 

drivers/usb/dwc3/core.h

@@ -1150,6 +1150,8 @@ 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 + DWC3_GUSB3PIPECTL_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 +1384,7 @@ struct dwc3 {
 	unsigned		sys_wakeup:1;
 	unsigned		wakeup_configured:1;
 	unsigned		suspended:1;
+	unsigned		susphy_state:1;
 
 	u16			imod_interval;