usb: gadget: tegra-xudc: Add handling for BLCG_COREPLL_PWRDN

The COREPLL_PWRDN bit in the BLCG register must be set when the XUSB
device controller is powergated and cleared when it is unpowergated.
If this bit is not explicitly controlled, the core PLL may remain in an
incorrect power state across suspend/resume or ELPG transitions.
Therefore, update the driver to explicitly control this bit during
powergate transitions.

Fixes: 49db427 ("usb: gadget: Add UDC driver for tegra XUSB device mode controller")
Cc: stable <stable@kernel.org>
Signed-off-by: Haotien Hsu <haotienh@nvidia.com>
Signed-off-by: Wayne Chang <waynec@nvidia.com>
Link: https://patch.msgid.link/20260123173121.4093902-1-waynec@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Haotien Hsu

drivers/usb/gadget/udc/tegra-xudc.c

@@ -3392,17 +3392,18 @@ static void tegra_xudc_device_params_init(struct tegra_xudc *xudc)
 {
 	u32 val, imod;
 
+	val = xudc_readl(xudc, BLCG);
 	if (xudc->soc->has_ipfs) {
-		val = xudc_readl(xudc, BLCG);
 		val |= BLCG_ALL;
 		val &= ~(BLCG_DFPCI | BLCG_UFPCI | BLCG_FE |
 				BLCG_COREPLL_PWRDN);
 		val |= BLCG_IOPLL_0_PWRDN;
 		val |= BLCG_IOPLL_1_PWRDN;
 		val |= BLCG_IOPLL_2_PWRDN;
-
-		xudc_writel(xudc, val, BLCG);
+	} else {
+		val &= ~BLCG_COREPLL_PWRDN;
 	}
+	xudc_writel(xudc, val, BLCG);
 
 	if (xudc->soc->port_speed_quirk)
 		tegra_xudc_limit_port_speed(xudc);
@@ -3953,6 +3954,7 @@ static void tegra_xudc_remove(struct platform_device *pdev)
 static int __maybe_unused tegra_xudc_powergate(struct tegra_xudc *xudc)
 {
 	unsigned long flags;
+	u32 val;
 
 	dev_dbg(xudc->dev, "entering ELPG\n");
 
@@ -3965,6 +3967,10 @@ static int __maybe_unused tegra_xudc_powergate(struct tegra_xudc *xudc)
 
 	spin_unlock_irqrestore(&xudc->lock, flags);
 
+	val = xudc_readl(xudc, BLCG);
+	val |= BLCG_COREPLL_PWRDN;
+	xudc_writel(xudc, val, BLCG);
+
 	clk_bulk_disable_unprepare(xudc->soc->num_clks, xudc->clks);
 
 	regulator_bulk_disable(xudc->soc->num_supplies, xudc->supplies);