arm: stm32mp: protect DBGMCU_IDC access with BSEC

As debugger must be totally closed on Sec closed chip,
the DBGMCU_IDC register is no more accessible (self
hosted debug is disabled with OTP).

This patch adds a function bsec_dbgswenable() to check
if the DBGMCU registers are available before to access them:
BSEC_DENABLE.DBGSWENABLE = self hosted debug status.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>

arch/arm/mach-stm32mp/bsec.c

@@ -8,6 +8,7 @@
 #include <log.h>
 #include <misc.h>
 #include <asm/io.h>
+#include <asm/arch/bsec.h>
 #include <asm/arch/stm32mp1_smc.h>
 #include <linux/arm-smccc.h>
 #include <linux/iopoll.h>
@@ -21,6 +22,7 @@
 #define BSEC_OTP_WRDATA_OFF		0x008
 #define BSEC_OTP_STATUS_OFF		0x00C
 #define BSEC_OTP_LOCK_OFF		0x010
+#define BSEC_DENABLE_OFF		0x014
 #define BSEC_DISTURBED_OFF		0x01C
 #define BSEC_ERROR_OFF			0x034
 #define BSEC_WRLOCK_OFF			0x04C /* OTP write permananet lock */
@@ -46,6 +48,9 @@
 #define BSEC_MODE_PROGFAIL_MASK		0x10
 #define BSEC_MODE_PWR_MASK		0x20
 
+/* DENABLE Register */
+#define BSEC_DENABLE_DBGSWENABLE	BIT(10)
+
 /*
  * OTP Lock services definition
  * Value must corresponding to the bit number in the register
@@ -506,3 +511,23 @@ U_BOOT_DRIVER(stm32mp_bsec) = {
 	.ops = &stm32mp_bsec_ops,
 	.probe = stm32mp_bsec_probe,
 };
+
+bool bsec_dbgswenable(void)
+{
+	struct udevice *dev;
+	struct stm32mp_bsec_platdata *plat;
+	int ret;
+
+	ret = uclass_get_device_by_driver(UCLASS_MISC,
+					  DM_GET_DRIVER(stm32mp_bsec), &dev);
+	if (ret || !dev) {
+		pr_debug("bsec driver not available\n");
+		return false;
+	}
+
+	plat = dev_get_platdata(dev);
+	if (readl(plat->base + BSEC_DENABLE_OFF) & BSEC_DENABLE_DBGSWENABLE)
+		return true;
+
+	return false;
+}

arch/arm/mach-stm32mp/cpu.c

@@ -12,6 +12,7 @@
 #include <misc.h>
 #include <net.h>
 #include <asm/io.h>
+#include <asm/arch/bsec.h>
 #include <asm/arch/stm32.h>
 #include <asm/arch/sys_proto.h>
 #include <dm/device.h>
@@ -155,7 +156,12 @@ static void dbgmcu_init(void)
 {
 	setbits_le32(RCC_DBGCFGR, RCC_DBGCFGR_DBGCKEN);
 
-	/* Freeze IWDG2 if Cortex-A7 is in debug mode */
+	/*
+	 * Freeze IWDG2 if Cortex-A7 is in debug mode
+	 * done in TF-A for TRUSTED boot and
+	 * DBGMCU access is controlled by BSEC_DENABLE.DBGSWENABLE
+	*/
+	if (!IS_ENABLED(CONFIG_TFABOOT) && bsec_dbgswenable())
 		setbits_le32(DBGMCU_APB4FZ1, DBGMCU_APB4FZ1_IWDG2);
 }
 #endif /* !defined(CONFIG_SPL) || defined(CONFIG_SPL_BUILD) */
@@ -276,11 +282,19 @@ void enable_caches(void)
 
 static u32 read_idc(void)
 {
+	/* DBGMCU access is controlled by BSEC_DENABLE.DBGSWENABLE */
+	if (bsec_dbgswenable()) {
 		setbits_le32(RCC_DBGCFGR, RCC_DBGCFGR_DBGCKEN);
 
 		return readl(DBGMCU_IDC);
 	}
 
+	if (CONFIG_IS_ENABLED(STM32MP15x))
+		return CPU_DEV_STM32MP15; /* STM32MP15x and unknown revision */
+	else
+		return 0x0;
+}
+
 u32 get_cpu_dev(void)
 {
 	return (read_idc() & DBGMCU_IDC_DEV_ID_MASK) >> DBGMCU_IDC_DEV_ID_SHIFT;

arch/arm/mach-stm32mp/include/mach/bsec.h

@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause */
+/*
+ * Copyright (C) 2020, STMicroelectronics - All Rights Reserved
+ */
+
+/* check self hosted debug status = BSEC_DENABLE.DBGSWENABLE */
+bool bsec_dbgswenable(void);