gpio: ws16c48: Implement get_multiple callback

The WinSystems WS16C48 device provides 48 lines of digital I/O accessed
via six 8-bit ports. Since eight input lines are acquired on a single
port input read, the WS16C48 GPIO driver may improve multiple input
reads by utilizing a get_multiple callback. This patch implements the
ws16c48_gpio_get_multiple function which serves as the respective
get_multiple callback.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-ws16c48.c b/drivers/gpio/gpio-ws16c48.c
index 746648244bf3..c7028eb0b8e1 100644
--- a/drivers/gpio/gpio-ws16c48.c
+++ b/drivers/gpio/gpio-ws16c48.c
@@ -11,6 +11,7 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  */
+#include <linux/bitmap.h>
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/errno.h>
@@ -129,6 +130,51 @@ static int ws16c48_gpio_get(struct gpio_chip *chip, unsigned offset)
         return !!(port_state & mask);
 }
 
+static int ws16c48_gpio_get_multiple(struct gpio_chip *chip,
+        unsigned long *mask, unsigned long *bits)
+{
+        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
+        const unsigned int gpio_reg_size = 8;
+        size_t i;
+        const size_t num_ports = chip->ngpio / gpio_reg_size;
+        unsigned int bits_offset;
+        size_t word_index;
+        unsigned int word_offset;
+        unsigned long word_mask;
+        const unsigned long port_mask = GENMASK(gpio_reg_size - 1, 0);
+        unsigned long port_state;
+
+        /* clear bits array to a clean slate */
+        bitmap_zero(bits, chip->ngpio);
+
+        /* get bits are evaluated a gpio port register at a time */
+        for (i = 0; i < num_ports; i++) {
+                /* gpio offset in bits array */
+                bits_offset = i * gpio_reg_size;
+
+                /* word index for bits array */
+                word_index = BIT_WORD(bits_offset);
+
+                /* gpio offset within current word of bits array */
+                word_offset = bits_offset % BITS_PER_LONG;
+
+                /* mask of get bits for current gpio within current word */
+                word_mask = mask[word_index] & (port_mask << word_offset);
+                if (!word_mask) {
+                        /* no get bits in this port so skip to next one */
+                        continue;
+                }
+
+                /* read bits from current gpio port */
+                port_state = inb(ws16c48gpio->base + i);
+
+                /* store acquired bits at respective bits array offset */
+                bits[word_index] |= port_state << word_offset;
+        }
+
+        return 0;
+}
+
 static void ws16c48_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 {
         struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
@@ -383,6 +429,7 @@ static int ws16c48_probe(struct device *dev, unsigned int id)
         ws16c48gpio->chip.direction_input = ws16c48_gpio_direction_input;
         ws16c48gpio->chip.direction_output = ws16c48_gpio_direction_output;
         ws16c48gpio->chip.get = ws16c48_gpio_get;
+        ws16c48gpio->chip.get_multiple = ws16c48_gpio_get_multiple;
         ws16c48gpio->chip.set = ws16c48_gpio_set;
         ws16c48gpio->chip.set_multiple = ws16c48_gpio_set_multiple;
         ws16c48gpio->base = base[id];