gpio: mmio: Fix up inverted direction registers

The bgpio_init() takes one of two arguments to specify a register
to set the direction of the GPIO line: either dirout that
indicates that a 1 in the bit in that register sets the
corresponding line to output, or dirin which indicates that
a 1 in the bit in that register sets the corresponding line to
input. Conversely setting the bit to 0 on these will turn the
line into input and output respectively. One of these can
be defined but not both.

This means that a platform that sets a bit to 1 for output
only defines dirout and a platform that sets a bit to 0 for
output only defines dirin. In short this defines the polarity
of the direction register.

Both can also be left as NULL meaning the GPIO chip is either
input only or output only.

Tomer Maimon discovered that for get/set chips (those where the
get and set registers are defined but no separate clear register,
and specifying BGPIOF_READ_OUTPUT_REG_SET so that we say we
want to read the output value from the SET register)
we are unconditionally reading the value from the SET register
when the direction bit is 1 and from the DAT register when the
direction bit is 0, not taking the direction bit polarity into
account.

It would be expected that when the direction bit is inverted
(dirin is defined but not dirout) we read the current value from
the DAT register when the bit is 1 and from the SET register
when the bit is 0.

Currently only some versions of ATH79, brcmstb, some versions of
CLP711x, GE, IOP and Loongson use the dirin mode (a 1 in the
register means input). They are unaffected because
BGPIOF_READ_OUTPUT_REG_SET is not set on any of them. (They
do not read back the SET register to figure out the output
value.) So this is no regression with current drivers.

However the behaviour is wrong and does not work with Tomer's
new driver where he needs to use the BGIOF_READ_OUTPUT_REG_SET.
This fixes the above issue by:

- Instead of defining separate functions for the inverted case,
  set up a flag in the gpio_chip that indicates that the
  direction is inverted.
- Remove the special inverted functions for setting
  input/output and getting the direction, rely on the flag
  instead.
- Respect this flag in bgpio_get_set() and
  bgpio_get_set_multiple()

Reported-by: Tomer Maimon <tmaimon77@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mmio.c

@@ -136,8 +136,20 @@ static unsigned long bgpio_line2mask(struct gpio_chip *gc, unsigned int line)
 static int bgpio_get_set(struct gpio_chip *gc, unsigned int gpio)
 {
 	unsigned long pinmask = bgpio_line2mask(gc, gpio);
+	bool dir = !!(gc->bgpio_dir & pinmask);
 
-	if (gc->bgpio_dir & pinmask)
+	/*
+	 * If the direction is OUT we read the value from the SET
+	 * register, and if the direction is IN we read the value
+	 * from the DAT register.
+	 *
+	 * If the direction bits are inverted, naturally this gets
+	 * inverted too.
+	 */
+	if (gc->bgpio_dir_inverted)
+		dir = !dir;
+
+	if (dir)
 		return !!(gc->read_reg(gc->reg_set) & pinmask);
 	else
 		return !!(gc->read_reg(gc->reg_dat) & pinmask);
@@ -157,8 +169,13 @@ static int bgpio_get_set_multiple(struct gpio_chip *gc, unsigned long *mask,
 	*bits &= ~*mask;
 
 	/* Exploit the fact that we know which directions are set */
-	set_mask = *mask & gc->bgpio_dir;
-	get_mask = *mask & ~gc->bgpio_dir;
+	if (gc->bgpio_dir_inverted) {
+		set_mask = *mask & ~gc->bgpio_dir;
+		get_mask = *mask & gc->bgpio_dir;
+	} else {
+		set_mask = *mask & gc->bgpio_dir;
+		get_mask = *mask & ~gc->bgpio_dir;
+	}
 
 	if (set_mask)
 		*bits |= gc->read_reg(gc->reg_set) & set_mask;
@@ -359,7 +376,10 @@ static int bgpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
 
 	spin_lock_irqsave(&gc->bgpio_lock, flags);
 
-	gc->bgpio_dir &= ~bgpio_line2mask(gc, gpio);
+	if (gc->bgpio_dir_inverted)
+		gc->bgpio_dir |= bgpio_line2mask(gc, gpio);
+	else
+		gc->bgpio_dir &= ~bgpio_line2mask(gc, gpio);
 	gc->write_reg(gc->reg_dir, gc->bgpio_dir);
 
 	spin_unlock_irqrestore(&gc->bgpio_lock, flags);
@@ -370,7 +390,10 @@ static int bgpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
 static int bgpio_get_dir(struct gpio_chip *gc, unsigned int gpio)
 {
 	/* Return 0 if output, 1 of input */
-	return !(gc->read_reg(gc->reg_dir) & bgpio_line2mask(gc, gpio));
+	if (gc->bgpio_dir_inverted)
+		return !!(gc->read_reg(gc->reg_dir) & bgpio_line2mask(gc, gpio));
+	else
+		return !(gc->read_reg(gc->reg_dir) & bgpio_line2mask(gc, gpio));
 }
 
 static int bgpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
@@ -381,37 +404,10 @@ static int bgpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
 
 	spin_lock_irqsave(&gc->bgpio_lock, flags);
 
-	gc->bgpio_dir |= bgpio_line2mask(gc, gpio);
-	gc->write_reg(gc->reg_dir, gc->bgpio_dir);
-
-	spin_unlock_irqrestore(&gc->bgpio_lock, flags);
-
-	return 0;
-}
-
-static int bgpio_dir_in_inv(struct gpio_chip *gc, unsigned int gpio)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&gc->bgpio_lock, flags);
-
-	gc->bgpio_dir |= bgpio_line2mask(gc, gpio);
-	gc->write_reg(gc->reg_dir, gc->bgpio_dir);
-
-	spin_unlock_irqrestore(&gc->bgpio_lock, flags);
-
-	return 0;
-}
-
-static int bgpio_dir_out_inv(struct gpio_chip *gc, unsigned int gpio, int val)
-{
-	unsigned long flags;
-
-	gc->set(gc, gpio, val);
-
-	spin_lock_irqsave(&gc->bgpio_lock, flags);
-
-	gc->bgpio_dir &= ~bgpio_line2mask(gc, gpio);
+	if (gc->bgpio_dir_inverted)
+		gc->bgpio_dir &= ~bgpio_line2mask(gc, gpio);
+	else
+		gc->bgpio_dir |= bgpio_line2mask(gc, gpio);
 	gc->write_reg(gc->reg_dir, gc->bgpio_dir);
 
 	spin_unlock_irqrestore(&gc->bgpio_lock, flags);
@@ -419,12 +415,6 @@ static int bgpio_dir_out_inv(struct gpio_chip *gc, unsigned int gpio, int val)
 	return 0;
 }
 
-static int bgpio_get_dir_inv(struct gpio_chip *gc, unsigned int gpio)
-{
-	/* Return 0 if output, 1 if input */
-	return !!(gc->read_reg(gc->reg_dir) & bgpio_line2mask(gc, gpio));
-}
-
 static int bgpio_setup_accessors(struct device *dev,
 				 struct gpio_chip *gc,
 				 bool byte_be)
@@ -560,9 +550,10 @@ static int bgpio_setup_direction(struct gpio_chip *gc,
 		gc->get_direction = bgpio_get_dir;
 	} else if (dirin) {
 		gc->reg_dir = dirin;
-		gc->direction_output = bgpio_dir_out_inv;
-		gc->direction_input = bgpio_dir_in_inv;
-		gc->get_direction = bgpio_get_dir_inv;
+		gc->direction_output = bgpio_dir_out;
+		gc->direction_input = bgpio_dir_in;
+		gc->get_direction = bgpio_get_dir;
+		gc->bgpio_dir_inverted = true;
 	} else {
 		if (flags & BGPIOF_NO_OUTPUT)
 			gc->direction_output = bgpio_dir_out_err;
@@ -582,6 +573,33 @@ static int bgpio_request(struct gpio_chip *chip, unsigned gpio_pin)
 	return -EINVAL;
 }
 
+/**
+ * bgpio_init() - Initialize generic GPIO accessor functions
+ * @gc: the GPIO chip to set up
+ * @dev: the parent device of the new GPIO chip (compulsory)
+ * @sz: the size (width) of the MMIO registers in bytes, typically 1, 2 or 4
+ * @dat: MMIO address for the register to READ the value of the GPIO lines, it
+ *	is expected that a 1 in the corresponding bit in this register means the
+ *	line is asserted
+ * @set: MMIO address for the register to SET the value of the GPIO lines, it is
+ *	expected that we write the line with 1 in this register to drive the GPIO line
+ *	high.
+ * @clr: MMIO address for the register to CLEAR the value of the GPIO lines, it is
+ *	expected that we write the line with 1 in this register to drive the GPIO line
+ *	low. It is allowed to leave this address as NULL, in that case the SET register
+ *	will be assumed to also clear the GPIO lines, by actively writing the line
+ *	with 0.
+ * @dirout: MMIO address for the register to set the line as OUTPUT. It is assumed
+ *	that setting a line to 1 in this register will turn that line into an
+ *	output line. Conversely, setting the line to 0 will turn that line into
+ *	an input. Either this or @dirin can be defined, but never both.
+ * @dirin: MMIO address for the register to set this line as INPUT. It is assumed
+ *	that setting a line to 1 in this register will turn that line into an
+ *	input line. Conversely, setting the line to 0 will turn that line into
+ *	an output. Either this or @dirout can be defined, but never both.
+ * @flags: Different flags that will affect the behaviour of the device, such as
+ *	endianness etc.
+ */
 int bgpio_init(struct gpio_chip *gc, struct device *dev,
 	       unsigned long sz, void __iomem *dat, void __iomem *set,
 	       void __iomem *clr, void __iomem *dirout, void __iomem *dirin,

include/linux/gpio/driver.h

@@ -201,6 +201,8 @@ static inline struct gpio_irq_chip *to_gpio_irq_chip(struct irq_chip *chip)
  * @reg_set: output set register (out=high) for generic GPIO
  * @reg_clr: output clear register (out=low) for generic GPIO
  * @reg_dir: direction setting register for generic GPIO
+ * @bgpio_dir_inverted: indicates that the direction register is inverted
+ *	(gpiolib private state variable)
  * @bgpio_bits: number of register bits used for a generic GPIO i.e.
  *	<register width> * 8
  * @bgpio_lock: used to lock chip->bgpio_data. Also, this is needed to keep
@@ -267,6 +269,7 @@ struct gpio_chip {
 	void __iomem *reg_set;
 	void __iomem *reg_clr;
 	void __iomem *reg_dir;
+	bool bgpio_dir_inverted;
 	int bgpio_bits;
 	spinlock_t bgpio_lock;
 	unsigned long bgpio_data;