[PATCH 2/5] gpio: 104-idi-48: Implement and utilize register structures

[William Breathitt Gray <william.gray@xxxxxxxxxx>]

Reduce magic numbers and improve code readability by implementing and
utilizing named register data structures.

Signed-off-by: William Breathitt Gray <william.gray@xxxxxxxxxx>
---
 drivers/gpio/gpio-104-idi-48.c | 128 ++++++++++++++++-----------------
 1 file changed, 63 insertions(+), 65 deletions(-)

diff --git a/drivers/gpio/gpio-104-idi-48.c b/drivers/gpio/gpio-104-idi-48.c
index 9521ece3ebef..1f8c556d9013 100644
--- a/drivers/gpio/gpio-104-idi-48.c
+++ b/drivers/gpio/gpio-104-idi-48.c
@@ -20,6 +20,7 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/spinlock.h>
+#include <linux/types.h>
 
 #define IDI_48_EXTENT 8
 #define MAX_NUM_IDI_48 max_num_isa_dev(IDI_48_EXTENT)
@@ -33,13 +34,28 @@ static unsigned int irq[MAX_NUM_IDI_48];
 module_param_hw_array(irq, uint, irq, NULL, 0);
 MODULE_PARM_DESC(irq, "ACCES 104-IDI-48 interrupt line numbers");
 
+/**
+ * struct idi_48_reg - device register structure
+ * @port0:	Port 0 Inputs
+ * @unused:	Unused
+ * @port1:	Port 1 Inputs
+ * @irq:	Read: IRQ Status Register/IRQ Clear
+ *		Write: IRQ Enable/Disable
+ */
+struct idi_48_reg {
+	u8 port0[3];
+	u8 unused;
+	u8 port1[3];
+	u8 irq;
+};
+
 /**
  * struct idi_48_gpio - GPIO device private data structure
  * @chip:	instance of the gpio_chip
  * @lock:	synchronization lock to prevent I/O race conditions
  * @ack_lock:	synchronization lock to prevent IRQ handler race conditions
  * @irq_mask:	input bits affected by interrupts
- * @base:	base port address of the GPIO device
+ * @reg:	I/O address offset for the device registers
  * @cos_enb:	Change-Of-State IRQ enable boundaries mask
  */
 struct idi_48_gpio {
@@ -47,7 +63,7 @@ struct idi_48_gpio {
 	raw_spinlock_t lock;
 	spinlock_t ack_lock;
 	unsigned char irq_mask[6];
-	void __iomem *base;
+	struct idi_48_reg __iomem *reg;
 	unsigned char cos_enb;
 };
 
@@ -64,39 +80,38 @@ static int idi_48_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
 static int idi_48_gpio_get(struct gpio_chip *chip, unsigned offset)
 {
 	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
-	unsigned i;
-	static const unsigned int register_offset[6] = { 0, 1, 2, 4, 5, 6 };
-	void __iomem *port_addr;
-	unsigned mask;
-
-	for (i = 0; i < 48; i += 8)
-		if (offset < i + 8) {
-			port_addr = idi48gpio->base + register_offset[i / 8];
-			mask = BIT(offset - i);
-
-			return !!(ioread8(port_addr) & mask);
-		}
-
-	/* The following line should never execute since offset < 48 */
-	return 0;
+	struct idi_48_reg __iomem *const reg = idi48gpio->reg;
+	const unsigned long boundary = offset / 8;
+	const unsigned long group = boundary / 3;
+	u8 __iomem *const port_addr = group ? reg->port1 : reg->port0;
+	const unsigned long in_port = boundary - (group * 3);
+	const unsigned long mask = BIT(offset % 8);
+
+	return !!(ioread8(port_addr + in_port) & mask);
 }
 
 static int idi_48_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
 	unsigned long *bits)
 {
 	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
+	struct idi_48_reg __iomem *const reg = idi48gpio->reg;
 	unsigned long offset;
 	unsigned long gpio_mask;
-	static const size_t ports[] = { 0, 1, 2, 4, 5, 6 };
-	void __iomem *port_addr;
+	unsigned long boundary;
+	unsigned long group;
+	unsigned long in_port;
+	u8 __iomem *port_addr;
 	unsigned long port_state;
 
 	/* clear bits array to a clean slate */
 	bitmap_zero(bits, chip->ngpio);
 
-	for_each_set_clump8(offset, gpio_mask, mask, ARRAY_SIZE(ports) * 8) {
-		port_addr = idi48gpio->base + ports[offset / 8];
-		port_state = ioread8(port_addr) & gpio_mask;
+	for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
+		boundary = offset / 8;
+		group = boundary / 3;
+		port_addr = group ? reg->port1 : reg->port0;
+		in_port = boundary - (group * 3);
+		port_state = ioread8(port_addr + in_port) & gpio_mask;
 
 		bitmap_set_value8(bits, port_state, offset);
 	}
@@ -113,30 +128,21 @@ static void idi_48_irq_mask(struct irq_data *data)
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
 	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
 	const unsigned offset = irqd_to_hwirq(data);
-	unsigned i;
-	unsigned mask;
-	unsigned boundary;
+	const unsigned long boundary = offset / 8;
+	const unsigned long mask = BIT(offset % 8);
 	unsigned long flags;
 
-	for (i = 0; i < 48; i += 8)
-		if (offset < i + 8) {
-			mask = BIT(offset - i);
-			boundary = i / 8;
-
-			idi48gpio->irq_mask[boundary] &= ~mask;
-
-			if (!idi48gpio->irq_mask[boundary]) {
-				idi48gpio->cos_enb &= ~BIT(boundary);
-
-				raw_spin_lock_irqsave(&idi48gpio->lock, flags);
+	idi48gpio->irq_mask[boundary] &= ~mask;
 
-				iowrite8(idi48gpio->cos_enb, idi48gpio->base + 7);
+	/* Exit early if there are still input lines with IRQ unmasked */
+	if (idi48gpio->irq_mask[boundary])
+		return;
 
-				raw_spin_unlock_irqrestore(&idi48gpio->lock, flags);
-			}
+	idi48gpio->cos_enb &= ~BIT(boundary);
 
-			return;
-		}
+	raw_spin_lock_irqsave(&idi48gpio->lock, flags);
+	iowrite8(idi48gpio->cos_enb, &idi48gpio->reg->irq);
+	raw_spin_unlock_irqrestore(&idi48gpio->lock, flags);
 }
 
 static void idi_48_irq_unmask(struct irq_data *data)
@@ -144,32 +150,24 @@ static void idi_48_irq_unmask(struct irq_data *data)
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
 	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
 	const unsigned offset = irqd_to_hwirq(data);
-	unsigned i;
-	unsigned mask;
-	unsigned boundary;
+	const unsigned long boundary = offset / 8;
+	const unsigned long mask = BIT(offset % 8);
 	unsigned prev_irq_mask;
 	unsigned long flags;
 
-	for (i = 0; i < 48; i += 8)
-		if (offset < i + 8) {
-			mask = BIT(offset - i);
-			boundary = i / 8;
-			prev_irq_mask = idi48gpio->irq_mask[boundary];
-
-			idi48gpio->irq_mask[boundary] |= mask;
+	prev_irq_mask = idi48gpio->irq_mask[boundary];
 
-			if (!prev_irq_mask) {
-				idi48gpio->cos_enb |= BIT(boundary);
+	idi48gpio->irq_mask[boundary] |= mask;
 
-				raw_spin_lock_irqsave(&idi48gpio->lock, flags);
+	/* Exit early if IRQ was already unmasked for this boundary */
+	if (prev_irq_mask)
+		return;
 
-				iowrite8(idi48gpio->cos_enb, idi48gpio->base + 7);
+	idi48gpio->cos_enb |= BIT(boundary);
 
-				raw_spin_unlock_irqrestore(&idi48gpio->lock, flags);
-			}
-
-			return;
-		}
+	raw_spin_lock_irqsave(&idi48gpio->lock, flags);
+	iowrite8(idi48gpio->cos_enb, &idi48gpio->reg->irq);
+	raw_spin_unlock_irqrestore(&idi48gpio->lock, flags);
 }
 
 static int idi_48_irq_set_type(struct irq_data *data, unsigned flow_type)
@@ -204,7 +202,7 @@ static irqreturn_t idi_48_irq_handler(int irq, void *dev_id)
 
 	raw_spin_lock(&idi48gpio->lock);
 
-	cos_status = ioread8(idi48gpio->base + 7);
+	cos_status = ioread8(&idi48gpio->reg->irq);
 
 	raw_spin_unlock(&idi48gpio->lock);
 
@@ -250,8 +248,8 @@ static int idi_48_irq_init_hw(struct gpio_chip *gc)
 	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(gc);
 
 	/* Disable IRQ by default */
-	iowrite8(0, idi48gpio->base + 7);
-	ioread8(idi48gpio->base + 7);
+	iowrite8(0, &idi48gpio->reg->irq);
+	ioread8(&idi48gpio->reg->irq);
 
 	return 0;
 }
@@ -273,8 +271,8 @@ static int idi_48_probe(struct device *dev, unsigned int id)
 		return -EBUSY;
 	}
 
-	idi48gpio->base = devm_ioport_map(dev, base[id], IDI_48_EXTENT);
-	if (!idi48gpio->base)
+	idi48gpio->reg = devm_ioport_map(dev, base[id], IDI_48_EXTENT);
+	if (!idi48gpio->reg)
 		return -ENOMEM;
 
 	idi48gpio->chip.label = name;
-- 
2.36.1