irqchip/stm32-exti: Skip secure events

Secure OS can reserve some EXTI events, marking them as "secure" by setting
the corresponding bit in register SECCFGR (aka TZENR).  These events cannot
be used by Linux.

Read the list of reserved events and check it during interrupt domain
allocation.

Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240415134926.1254428-6-antonio.borneo@foss.st.com

Author: AntonioBorneo

drivers/irqchip/irq-stm32-exti.c

@@ -36,6 +36,7 @@ struct stm32_exti_bank {
 	u32 rpr_ofst;
 	u32 fpr_ofst;
 	u32 trg_ofst;
+	u32 seccfgr_ofst;
 };
 
 #define UNDEF_REG ~0
@@ -54,10 +55,12 @@ struct stm32_exti_chip_data {
 	u32 mask_cache;
 	u32 rtsr_cache;
 	u32 ftsr_cache;
+	u32 event_reserved;
 };
 
 struct stm32_exti_host_data {
 	void __iomem *base;
+	struct device *dev;
 	struct stm32_exti_chip_data *chips_data;
 	const struct stm32_exti_drv_data *drv_data;
 	struct hwspinlock *hwlock;
@@ -73,6 +76,7 @@ static const struct stm32_exti_bank stm32f4xx_exti_b1 = {
 	.rpr_ofst	= 0x14,
 	.fpr_ofst	= UNDEF_REG,
 	.trg_ofst	= UNDEF_REG,
+	.seccfgr_ofst	= UNDEF_REG,
 };
 
 static const struct stm32_exti_bank *stm32f4xx_exti_banks[] = {
@@ -93,6 +97,7 @@ static const struct stm32_exti_bank stm32h7xx_exti_b1 = {
 	.rpr_ofst	= 0x88,
 	.fpr_ofst	= UNDEF_REG,
 	.trg_ofst	= UNDEF_REG,
+	.seccfgr_ofst	= UNDEF_REG,
 };
 
 static const struct stm32_exti_bank stm32h7xx_exti_b2 = {
@@ -104,6 +109,7 @@ static const struct stm32_exti_bank stm32h7xx_exti_b2 = {
 	.rpr_ofst	= 0x98,
 	.fpr_ofst	= UNDEF_REG,
 	.trg_ofst	= UNDEF_REG,
+	.seccfgr_ofst	= UNDEF_REG,
 };
 
 static const struct stm32_exti_bank stm32h7xx_exti_b3 = {
@@ -115,6 +121,7 @@ static const struct stm32_exti_bank stm32h7xx_exti_b3 = {
 	.rpr_ofst	= 0xA8,
 	.fpr_ofst	= UNDEF_REG,
 	.trg_ofst	= UNDEF_REG,
+	.seccfgr_ofst	= UNDEF_REG,
 };
 
 static const struct stm32_exti_bank *stm32h7xx_exti_banks[] = {
@@ -137,6 +144,7 @@ static const struct stm32_exti_bank stm32mp1_exti_b1 = {
 	.rpr_ofst	= 0x0C,
 	.fpr_ofst	= 0x10,
 	.trg_ofst	= 0x3EC,
+	.seccfgr_ofst	= 0x14,
 };
 
 static const struct stm32_exti_bank stm32mp1_exti_b2 = {
@@ -148,6 +156,7 @@ static const struct stm32_exti_bank stm32mp1_exti_b2 = {
 	.rpr_ofst	= 0x2C,
 	.fpr_ofst	= 0x30,
 	.trg_ofst	= 0x3E8,
+	.seccfgr_ofst	= 0x34,
 };
 
 static const struct stm32_exti_bank stm32mp1_exti_b3 = {
@@ -159,6 +168,7 @@ static const struct stm32_exti_bank stm32mp1_exti_b3 = {
 	.rpr_ofst	= 0x4C,
 	.fpr_ofst	= 0x50,
 	.trg_ofst	= 0x3E4,
+	.seccfgr_ofst	= 0x54,
 };
 
 static const struct stm32_exti_bank *stm32mp1_exti_banks[] = {
@@ -706,6 +716,12 @@ static int stm32_exti_h_domain_alloc(struct irq_domain *dm,
 	bank  = hwirq / IRQS_PER_BANK;
 	chip_data = &host_data->chips_data[bank];
 
+	/* Check if event is reserved (Secure) */
+	if (chip_data->event_reserved & BIT(hwirq % IRQS_PER_BANK)) {
+		dev_err(host_data->dev, "event %lu is reserved, secure\n", hwirq);
+		return -EPERM;
+	}
+
 	event_trg = readl_relaxed(host_data->base + chip_data->reg_bank->trg_ofst);
 	chip = (event_trg & BIT(hwirq % IRQS_PER_BANK)) ?
 	       &stm32_exti_h_chip : &stm32_exti_h_chip_direct;
@@ -803,6 +819,10 @@ stm32_exti_chip_data *stm32_exti_chip_init(struct stm32_exti_host_data *h_data,
 	if (stm32_bank->emr_ofst != UNDEF_REG)
 		writel_relaxed(0, base + stm32_bank->emr_ofst);
 
+	/* reserve Secure events */
+	if (stm32_bank->seccfgr_ofst != UNDEF_REG)
+		chip_data->event_reserved = readl_relaxed(base + stm32_bank->seccfgr_ofst);
+
 	pr_info("%pOF: bank%d\n", node, bank_idx);
 
 	return chip_data;
@@ -908,6 +928,7 @@ static int stm32_exti_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	dev_set_drvdata(dev, host_data);
+	host_data->dev = dev;
 
 	/* check for optional hwspinlock which may be not available yet */
 	ret = of_hwspin_lock_get_id(np, 0);