pinctrl: stm32: prevent the use of the secure protected pins

The hardware denies any access from the Linux non-secure world to the
secure-protected pins. Hence, prevent any driver to request such a pin.

Mark the secure-protected GPIO lines as invalid (.init_valid_mask) and
prevent the pinmux request / pinconf setting operations.
Identify the secure pins with "NO ACCESS" in the pinconf sysfs.

Signed-off-by: Fabien Dessenne <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/stm32/pinctrl-stm32.c

···
 #define STM32_GPIO_LCKR		0x1c
 #define STM32_GPIO_AFRL		0x20
 #define STM32_GPIO_AFRH		0x24
+#define STM32_GPIO_SECCFGR	0x30
 
 /* custom bitfield to backup pin status */
 #define STM32_GPIO_BKP_MODE_SHIFT	0
···
 	u32 bank_ioport_nr;
 	u32 pin_backup[STM32_GPIO_PINS_PER_BANK];
 	u8 irq_type[STM32_GPIO_PINS_PER_BANK];
+	bool secure_control;
 };
 
 struct stm32_pinctrl {
···
 	return ret;
 }
 
+static int stm32_gpio_init_valid_mask(struct gpio_chip *chip,
+				      unsigned long *valid_mask,
+				      unsigned int ngpios)
+{
+	struct stm32_gpio_bank *bank = gpiochip_get_data(chip);
+	struct stm32_pinctrl *pctl = dev_get_drvdata(bank->gpio_chip.parent);
+	unsigned int i;
+	u32 sec;
+
+	/* All gpio are valid per default */
+	bitmap_fill(valid_mask, ngpios);
+
+	if (bank->secure_control) {
+		/* Tag secured pins as invalid */
+		sec = readl_relaxed(bank->base + STM32_GPIO_SECCFGR);
+
+		for (i = 0; i < ngpios; i++) {
+			if (sec & BIT(i)) {
+				clear_bit(i, valid_mask);
+				dev_dbg(pctl->dev, "No access to gpio %d - %d\n", bank->bank_nr, i);
+			}
+		}
+	}
+
+	return 0;
+}
+
 static const struct gpio_chip stm32_gpio_template = {
 	.request		= stm32_gpio_request,
 	.free			= stm32_gpio_free,
···
 	.to_irq			= stm32_gpio_to_irq,
 	.get_direction		= stm32_gpio_get_direction,
 	.set_config		= gpiochip_generic_config,
+	.init_valid_mask	= stm32_gpio_init_valid_mask,
 };
 
 static void stm32_gpio_irq_trigger(struct irq_data *d)
···
 	return stm32_pmx_set_mode(bank, pin, !input, 0);
 }
 
+static int stm32_pmx_request(struct pinctrl_dev *pctldev, unsigned int gpio)
+{
+	struct stm32_pinctrl *pctl = pinctrl_dev_get_drvdata(pctldev);
+	struct pinctrl_gpio_range *range;
+
+	range = pinctrl_find_gpio_range_from_pin_nolock(pctldev, gpio);
+	if (!range) {
+		dev_err(pctl->dev, "No gpio range defined.\n");
+		return -EINVAL;
+	}
+
+	if (!gpiochip_line_is_valid(range->gc, stm32_gpio_pin(gpio))) {
+		dev_warn(pctl->dev, "Can't access gpio %d\n", gpio);
+		return -EACCES;
+	}
+
+	return 0;
+}
+
 static const struct pinmux_ops stm32_pmx_ops = {
 	.get_functions_count	= stm32_pmx_get_funcs_cnt,
 	.get_function_name	= stm32_pmx_get_func_name,
 	.get_function_groups	= stm32_pmx_get_func_groups,
 	.set_mux		= stm32_pmx_set_mux,
 	.gpio_set_direction	= stm32_pmx_gpio_set_direction,
+	.request		= stm32_pmx_request,
 	.strict			= true,
 };
 
···
 	bank = gpiochip_get_data(range->gc);
 	offset = stm32_gpio_pin(pin);
 
+	if (!gpiochip_line_is_valid(range->gc, offset)) {
+		dev_warn(pctl->dev, "Can't access gpio %d\n", pin);
+		return -EACCES;
+	}
+
 	switch (param) {
 	case PIN_CONFIG_DRIVE_PUSH_PULL:
 		ret = stm32_pconf_set_driving(bank, offset, 0);
···
 	bank = gpiochip_get_data(range->gc);
 	offset = stm32_gpio_pin(pin);
 
+	if (!gpiochip_line_is_valid(range->gc, offset)) {
+		seq_puts(s, "NO ACCESS");
+		return;
+	}
+
 	stm32_pmx_get_mode(bank, offset, &mode, &alt);
 	bias = stm32_pconf_get_bias(bank, offset);
 
···
 	bank->gpio_chip.parent = dev;
 	bank->bank_nr = bank_nr;
 	bank->bank_ioport_nr = bank_ioport_nr;
+	bank->secure_control = pctl->match_data->secure_control;
 	spin_lock_init(&bank->lock);
 
 	/* create irq hierarchical domain */
···
 
 	range = pinctrl_find_gpio_range_from_pin(pctl->pctl_dev, pin);
 	if (!range)
+		return 0;
+
+	if (!gpiochip_line_is_valid(range->gc, offset))
 		return 0;
 
 	pin_is_irq = gpiochip_line_is_irq(range->gc, offset);

drivers/pinctrl/stm32/pinctrl-stm32.h

···
 struct stm32_pinctrl_match_data {
 	const struct stm32_desc_pin *pins;
 	const unsigned int npins;
+	bool secure_control;
 };
 
 struct stm32_gpio_bank;

drivers/pinctrl/stm32/pinctrl-stm32mp135.c

···
 static struct stm32_pinctrl_match_data stm32mp135_match_data = {
 	.pins = stm32mp135_pins,
 	.npins = ARRAY_SIZE(stm32mp135_pins),
+	.secure_control = true,
 };
 
 static const struct of_device_id stm32mp135_pctrl_match[] = {