usb: misc: qcom_eud: Access EUD_MODE_MANAGER2 through secure calls

EUD_MODE_MANAGER2 register is mapped to a memory region that is marked
as read-only for operating system running at EL1, enforcing access
restrictions that prohibit direct memory-mapped writes via writel().

Attempts to write to this region from HLOS can result in silent failures
or memory access violations, particularly when toggling EUD (Embedded
USB Debugger) state. To ensure secure register access, modify the driver
to use qcom_scm_io_writel(), which routes the write operation to Qualcomm
Secure Channel Monitor (SCM). SCM has the necessary permissions to access
protected memory regions, enabling reliable control over EUD state.

SC7280, the only user of EUD is also affected, indicating that this could
never have worked on a properly fused device.

Fixes: 9a1bf58ccd44 ("usb: misc: eud: Add driver support for Embedded USB Debugger(EUD)")
Signed-off-by: Melody Olvera <[e-mail]>
Reviewed-by: Konrad Dybcio <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Reviewed-by: Souradeep Chowdhury <[e-mail]>
Signed-off-by: Komal Bajaj <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/Kconfig

···
 config USB_QCOM_EUD
 	tristate "QCOM Embedded USB Debugger(EUD) Driver"
 	depends on ARCH_QCOM || COMPILE_TEST
+	select QCOM_SCM
 	select USB_ROLE_SWITCH
 	help
 	  This module enables support for Qualcomm Technologies, Inc.

drivers/usb/misc/qcom_eud.c

···
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 #include <linux/usb/role.h>
+#include <linux/firmware/qcom/qcom_scm.h>
 
 #define EUD_REG_INT1_EN_MASK	0x0024
 #define EUD_REG_INT_STATUS_1	0x0044
···
 	struct device			*dev;
 	struct usb_role_switch		*role_sw;
 	void __iomem			*base;
-	void __iomem			*mode_mgr;
+	phys_addr_t			mode_mgr;
 	unsigned int			int_status;
 	int				irq;
 	bool				enabled;
···
 
 static int enable_eud(struct eud_chip *priv)
 {
+	int ret;
+
+	ret = qcom_scm_io_writel(priv->mode_mgr + EUD_REG_EUD_EN2, 1);
+	if (ret)
+		return ret;
+
 	writel(EUD_ENABLE, priv->base + EUD_REG_CSR_EUD_EN);
 	writel(EUD_INT_VBUS | EUD_INT_SAFE_MODE,
 			priv->base + EUD_REG_INT1_EN_MASK);
-	writel(1, priv->mode_mgr + EUD_REG_EUD_EN2);
 
 	return usb_role_switch_set_role(priv->role_sw, USB_ROLE_DEVICE);
 }
 
-static void disable_eud(struct eud_chip *priv)
+static int disable_eud(struct eud_chip *priv)
 {
+	int ret;
+
+	ret = qcom_scm_io_writel(priv->mode_mgr + EUD_REG_EUD_EN2, 0);
+	if (ret)
+		return ret;
+
 	writel(0, priv->base + EUD_REG_CSR_EUD_EN);
-	writel(0, priv->mode_mgr + EUD_REG_EUD_EN2);
+	return 0;
 }
 
 static ssize_t enable_show(struct device *dev,
···
 			chip->enabled = enable;
 		else
 			disable_eud(chip);
+
 	} else {
-		disable_eud(chip);
+		ret = disable_eud(chip);
 	}
 
-	return count;
+	return ret < 0 ? ret : count;
 }
 
 static DEVICE_ATTR_RW(enable);
···
 static int eud_probe(struct platform_device *pdev)
 {
 	struct eud_chip *chip;
+	struct resource *res;
 	int ret;
 
 	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
···
 	if (IS_ERR(chip->base))
 		return PTR_ERR(chip->base);
 
-	chip->mode_mgr = devm_platform_ioremap_resource(pdev, 1);
-	if (IS_ERR(chip->mode_mgr))
-		return PTR_ERR(chip->mode_mgr);
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	if (!res)
+		return -ENODEV;
+	chip->mode_mgr = res->start;
 
 	chip->irq = platform_get_irq(pdev, 0);
 	if (chip->irq < 0)