[PATCH] gpio: tegra186: Fix tegra186_gpio_is_accessible() check

[Prathamesh Shete <pshete@nvidia.com>]

The controller has several register bits describing access control
information for a given GPIO pin. When SCR_SEC_[R|W]EN is unset, it
means we have full read/write access to all the registers for given GPIO
pin. When SCR_SEC[R|W]EN is set, it means we need to further check the
accompanying SCR_SEC_G1[R|W] bit to determine read/write access to all
the registers for given GPIO pin.

This check was previously declaring that a GPIO pin was accessible
only if either of the following conditions were met:

  - SCR_SEC_REN + SCR_SEC_WEN both set

    or

  - SCR_SEC_REN + SCR_SEC_WEN both set and
    SCR_SEC_G1R + SCR_SEC_G1W both set

Update the check to properly handle cases where only one of
SCR_SEC_REN or SCR_SEC_WEN is set.

Fixes: b2b56a163230 ("gpio: tegra186: Check GPIO pin permission before access.")
Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
---
 drivers/gpio/gpio-tegra186.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpio-tegra186.c b/drivers/gpio/gpio-tegra186.c
index d87dd06db40d..54c8b02eec22 100644
--- a/drivers/gpio/gpio-tegra186.c
+++ b/drivers/gpio/gpio-tegra186.c
@@ -36,12 +36,10 @@
 #define  TEGRA186_GPIO_SCR_SEC_REN		BIT(27)
 #define  TEGRA186_GPIO_SCR_SEC_G1W		BIT(9)
 #define  TEGRA186_GPIO_SCR_SEC_G1R		BIT(1)
-#define  TEGRA186_GPIO_FULL_ACCESS		(TEGRA186_GPIO_SCR_SEC_WEN | \
-						 TEGRA186_GPIO_SCR_SEC_REN | \
-						 TEGRA186_GPIO_SCR_SEC_G1R | \
+#define  TEGRA186_GPIO_READ_ACCESS		(TEGRA186_GPIO_SCR_SEC_REN | \
+						 TEGRA186_GPIO_SCR_SEC_G1R)
+#define  TEGRA186_GPIO_WRITE_ACCESS		(TEGRA186_GPIO_SCR_SEC_WEN | \
 						 TEGRA186_GPIO_SCR_SEC_G1W)
-#define  TEGRA186_GPIO_SCR_SEC_ENABLE		(TEGRA186_GPIO_SCR_SEC_WEN | \
-						 TEGRA186_GPIO_SCR_SEC_REN)
 
 /* control registers */
 #define TEGRA186_GPIO_ENABLE_CONFIG 0x00
@@ -177,10 +175,18 @@ static inline bool tegra186_gpio_is_accessible(struct tegra_gpio *gpio, unsigned
 
 	value = __raw_readl(secure + TEGRA186_GPIO_SCR);
 
-	if ((value & TEGRA186_GPIO_SCR_SEC_ENABLE) == 0)
-		return true;
+	/*
+	 * When SCR_SEC_[R|W]EN is unset, then we have full read/write access to all the
+	 * registers for given GPIO pin.
+	 * When SCR_SEC[R|W]EN is set, then there is need to further check the accompanying
+	 * SCR_SEC_G1[R|W] bit to determine read/write access to all the registers for given
+	 * GPIO pin.
+	 */
 
-	if ((value & TEGRA186_GPIO_FULL_ACCESS) == TEGRA186_GPIO_FULL_ACCESS)
+	if (((value & TEGRA186_GPIO_SCR_SEC_REN) == 0 ||
+	     (value & TEGRA186_GPIO_READ_ACCESS)) &&
+	    ((value & TEGRA186_GPIO_SCR_SEC_WEN) == 0 ||
+	     (value & TEGRA186_GPIO_WRITE_ACCESS)))
 		return true;
 
 	return false;
-- 
2.17.1