gpio: rcar: Optimize GPIO pin state read on R-Car Gen3

Currently, the R-Car GPIO driver treats R-Car Gen2 and R-Car Gen3 GPIO
controllers the same.  However, there exist small differences, like the
behavior of the General Input Register (INDT):
  - On R-Car Gen1, R-Car Gen2, and RZ/G1, INDT only reflects the state
    of an input pin if the GPIO is configured for input,
  - On R-Car Gen3 and RZ/G2, INDT always reflects the state of the input
    pins.
Hence to accommodate all variants, the driver does not use the INDT
register to read the status of a GPIO line when configured for output,
at the expense of doing 2 or 3 register reads instead of 1.

Given register accesses are slow, change the .get() and .get_multiple()
callbacks to always use INDT to read pin state on SoCs where this is
supported.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
index f3b8c4b..edded64 100644 (file)
--- a/drivers/gpio/gpio-rcar.c
+++ b/drivers/gpio/gpio-rcar.c
@@ -35,6 +35,7 @@ struct gpio_rcar_bank_info {
 struct gpio_rcar_info {
        bool has_outdtsel;
        bool has_both_edge_trigger;
+       bool has_always_in;
 };
 
 struct gpio_rcar_priv {
@@ -302,9 +303,11 @@ static int gpio_rcar_get(struct gpio_chip *chip, unsigned offset)
        struct gpio_rcar_priv *p = gpiochip_get_data(chip);
        u32 bit = BIT(offset);
 
-       /* testing on r8a7790 shows that INDT does not show correct pin state
-        * when configured as output, so use OUTDT in case of output pins */
-       if (gpio_rcar_read(p, INOUTSEL) & bit)
+       /*
+        * Before R-Car Gen3, INDT does not show correct pin state when
+        * configured as output, so use OUTDT in case of output pins
+        */
+       if (!p->info.has_always_in && (gpio_rcar_read(p, INOUTSEL) & bit))
                return !!(gpio_rcar_read(p, OUTDT) & bit);
        else
                return !!(gpio_rcar_read(p, INDT) & bit);
@@ -324,6 +327,11 @@ static int gpio_rcar_get_multiple(struct gpio_chip *chip, unsigned long *mask,
        if (!bankmask)
                return 0;
 
+       if (p->info.has_always_in) {
+               bits[0] = gpio_rcar_read(p, INDT) & bankmask;
+               return 0;
+       }
+
        spin_lock_irqsave(&p->lock, flags);
        outputs = gpio_rcar_read(p, INOUTSEL);
        m = outputs & bankmask;
@@ -383,11 +391,19 @@ static int gpio_rcar_direction_output(struct gpio_chip *chip, unsigned offset,
 static const struct gpio_rcar_info gpio_rcar_info_gen1 = {
        .has_outdtsel = false,
        .has_both_edge_trigger = false,
+       .has_always_in = false,
 };
 
 static const struct gpio_rcar_info gpio_rcar_info_gen2 = {
        .has_outdtsel = true,
        .has_both_edge_trigger = true,
+       .has_always_in = false,
+};
+
+static const struct gpio_rcar_info gpio_rcar_info_gen3 = {
+       .has_outdtsel = true,
+       .has_both_edge_trigger = true,
+       .has_always_in = true,
 };
 
 static const struct of_device_id gpio_rcar_of_table[] = {
@@ -399,8 +415,7 @@ static const struct of_device_id gpio_rcar_of_table[] = {
                .data = &gpio_rcar_info_gen2,
        }, {
                .compatible = "renesas,rcar-gen3-gpio",
-               /* Gen3 GPIO is identical to Gen2. */
-               .data = &gpio_rcar_info_gen2,
+               .data = &gpio_rcar_info_gen3,
        }, {
                .compatible = "renesas,gpio-rcar",
                .data = &gpio_rcar_info_gen1,