usb: host: ohci-at91: add support to enter suspend using SMC

When Linux is running under OP-TEE, the SFR is set as secured and thus
the AT91_OHCIICR_USB_SUSPEND register isn't accessible. Add a SMC to
do the appropriate call to suspend the controller.
The SMC id is fetched from the device-tree property
"microchip,suspend-smc-id". if present, then the syscon regmap is not
used to enter suspend and a SMC is issued.

Reviewed-by: Claudiu Beznea <[e-mail]>
Acked-by: Alan Stern <[e-mail]>
Signed-off-by: Clément Léger <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/ohci-at91.c

···
  * This file is licenced under the GPL.
  */
 
+#include <linux/arm-smccc.h>
 #include <linux/clk.h>
 #include <linux/dma-mapping.h>
 #include <linux/gpio/consumer.h>
···
 	bool clocked;
 	bool wakeup;		/* Saved wake-up state for resume */
 	struct regmap *sfr_regmap;
+	u32 suspend_smc_id;
 };
 /* interface and function clocks; sometimes also an AHB clock */
 
···
 /*-------------------------------------------------------------------------*/
 
 static void usb_hcd_at91_remove (struct usb_hcd *, struct platform_device *);
+
+static u32 at91_dt_suspend_smc(struct device *dev)
+{
+	u32 suspend_smc_id;
+
+	if (!dev->of_node)
+		return 0;
+
+	if (of_property_read_u32(dev->of_node, "microchip,suspend-smc-id", &suspend_smc_id))
+		return 0;
+
+	return suspend_smc_id;
+}
 
 static struct regmap *at91_dt_syscon_sfr(void)
 {
···
 		goto err;
 	}
 
-	ohci_at91->sfr_regmap = at91_dt_syscon_sfr();
-	if (!ohci_at91->sfr_regmap)
-		dev_dbg(dev, "failed to find sfr node\n");
+	ohci_at91->suspend_smc_id = at91_dt_suspend_smc(dev);
+	if (!ohci_at91->suspend_smc_id)  {
+		dev_dbg(dev, "failed to find sfr suspend smc id, using regmap\n");
+		ohci_at91->sfr_regmap = at91_dt_syscon_sfr();
+		if (!ohci_at91->sfr_regmap)
+			dev_dbg(dev, "failed to find sfr node\n");
+	}
 
 	board = hcd->self.controller->platform_data;
 	ohci = hcd_to_ohci(hcd);
···
 	return length;
 }
 
-static int ohci_at91_port_suspend(struct regmap *regmap, u8 set)
+static int ohci_at91_port_suspend(struct ohci_at91_priv *ohci_at91, u8 set)
 {
+	struct regmap *regmap = ohci_at91->sfr_regmap;
 	u32 regval;
 	int ret;
 
-	if (!regmap)
-		return 0;
+	if (ohci_at91->suspend_smc_id) {
+		struct arm_smccc_res res;
 
-	ret = regmap_read(regmap, AT91_SFR_OHCIICR, &regval);
-	if (ret)
-		return ret;
+		arm_smccc_smc(ohci_at91->suspend_smc_id, set, 0, 0, 0, 0, 0, 0, &res);
+		if (res.a0)
+			return -EINVAL;
+	} else if (regmap) {
+		ret = regmap_read(regmap, AT91_SFR_OHCIICR, &regval);
+		if (ret)
+			return ret;
 
-	if (set)
-		regval |= AT91_OHCIICR_USB_SUSPEND;
-	else
-		regval &= ~AT91_OHCIICR_USB_SUSPEND;
+		if (set)
+			regval |= AT91_OHCIICR_USB_SUSPEND;
+		else
+			regval &= ~AT91_OHCIICR_USB_SUSPEND;
 
-	regmap_write(regmap, AT91_SFR_OHCIICR, regval);
+		regmap_write(regmap, AT91_SFR_OHCIICR, regval);
+	}
 
 	return 0;
 }
···
 
 		case USB_PORT_FEAT_SUSPEND:
 			dev_dbg(hcd->self.controller, "SetPortFeat: SUSPEND\n");
-			if (valid_port(wIndex) && ohci_at91->sfr_regmap) {
-				ohci_at91_port_suspend(ohci_at91->sfr_regmap,
-						       1);
+			if (valid_port(wIndex)) {
+				ohci_at91_port_suspend(ohci_at91, 1);
 				return 0;
 			}
 			break;
···
 
 		case USB_PORT_FEAT_SUSPEND:
 			dev_dbg(hcd->self.controller, "ClearPortFeature: SUSPEND\n");
-			if (valid_port(wIndex) && ohci_at91->sfr_regmap) {
-				ohci_at91_port_suspend(ohci_at91->sfr_regmap,
-						       0);
+			if (valid_port(wIndex)) {
+				ohci_at91_port_suspend(ohci_at91, 0);
 				return 0;
 			}
 			break;
···
 		/* flush the writes */
 		(void) ohci_readl (ohci, &ohci->regs->control);
 		msleep(1);
-		ohci_at91_port_suspend(ohci_at91->sfr_regmap, 1);
+		ohci_at91_port_suspend(ohci_at91, 1);
 		at91_stop_clock(ohci_at91);
 	} else {
-		ohci_at91_port_suspend(ohci_at91->sfr_regmap, 1);
+		ohci_at91_port_suspend(ohci_at91, 1);
 	}
 
 	return ret;
···
 	struct usb_hcd	*hcd = dev_get_drvdata(dev);
 	struct ohci_at91_priv *ohci_at91 = hcd_to_ohci_at91_priv(hcd);
 
-	ohci_at91_port_suspend(ohci_at91->sfr_regmap, 0);
+	ohci_at91_port_suspend(ohci_at91, 0);
 
 	if (ohci_at91->wakeup)
 		disable_irq_wake(hcd->irq);