phy: renesas: rcar-gen3-usb2: Assert PLL reset on PHY power off

Assert PLL reset on PHY power off. This saves power.

Fixes: f3b5a8d ("phy: rcar-gen3-usb2: Add R-Car Gen3 USB2 PHY driver")
Cc: stable@vger.kernel.org
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://lore.kernel.org/r/20250507125032.565017-5-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/renesas/phy-rcar-gen3-usb2.c

@@ -537,9 +537,17 @@ static int rcar_gen3_phy_usb2_power_off(struct phy *p)
 	struct rcar_gen3_chan *channel = rphy->ch;
 	int ret = 0;
 
-	scoped_guard(spinlock_irqsave, &channel->lock)
+	scoped_guard(spinlock_irqsave, &channel->lock) {
 		rphy->powered = false;
 
+		if (rcar_gen3_are_all_rphys_power_off(channel)) {
+			u32 val = readl(channel->base + USB2_USBCTR);
+
+			val |= USB2_USBCTR_PLL_RST;
+			writel(val, channel->base + USB2_USBCTR);
+		}
+	}
+
 	if (channel->vbus)
 		ret = regulator_disable(channel->vbus);