pinctrl: sun4i: GPIOs configured as irq must be set to input before reading

On sun4i-a10, when GPIOs are configured as external interrupt the value for
them in the data register does not seem to get updated, so set their mux to
input (and restore afterwards) when reading the pin.

Missed edges seem to be buffered, so this does not introduce a race
condition.

I've also tested this on sun5i-a13 and sun7i-a20 and those do not seem to
be affected, the input value representation in the data register does seem
to correctly get updated to the actual pin value while in irq mode there.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

3 files changed, 17 insertions, 2 deletions

diff --git a/drivers/pinctrl/sunxi/pinctrl-sun4i-a10.c b/drivers/pinctrl/sunxi/pinctrl-sun4i-a10.c
index 24c5d88f943f..3c68a8e5e0dd 100644
--- a/drivers/pinctrl/sunxi/pinctrl-sun4i-a10.c
+++ b/drivers/pinctrl/sunxi/pinctrl-sun4i-a10.c
@@ -1011,6 +1011,7 @@ static const struct sunxi_pinctrl_desc sun4i_a10_pinctrl_data = {
         .pins = sun4i_a10_pins,
         .npins = ARRAY_SIZE(sun4i_a10_pins),
         .irq_banks = 1,
+        .irq_read_needs_mux = true,
 };
 
 static int sun4i_a10_pinctrl_probe(struct platform_device *pdev)
diff --git a/drivers/pinctrl/sunxi/pinctrl-sunxi.c b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
index 3d0744337736..f8e171b76693 100644
--- a/drivers/pinctrl/sunxi/pinctrl-sunxi.c
+++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
@@ -29,6 +29,7 @@
 #include <linux/slab.h>
 
 #include "../core.h"
+#include "../../gpio/gpiolib.h"
 #include "pinctrl-sunxi.h"
 
 static struct irq_chip sunxi_pinctrl_edge_irq_chip;
@@ -464,10 +465,19 @@ static int sunxi_pinctrl_gpio_direction_input(struct gpio_chip *chip,
 static int sunxi_pinctrl_gpio_get(struct gpio_chip *chip, unsigned offset)
 {
         struct sunxi_pinctrl *pctl = dev_get_drvdata(chip->dev);
-
         u32 reg = sunxi_data_reg(offset);
         u8 index = sunxi_data_offset(offset);
-        u32 val = (readl(pctl->membase + reg) >> index) & DATA_PINS_MASK;
+        u32 set_mux = pctl->desc->irq_read_needs_mux &&
+                        test_bit(FLAG_USED_AS_IRQ, &chip->desc[offset].flags);
+        u32 val;
+
+        if (set_mux)
+                sunxi_pmx_set(pctl->pctl_dev, offset, SUN4I_FUNC_INPUT);
+
+        val = (readl(pctl->membase + reg) >> index) & DATA_PINS_MASK;
+
+        if (set_mux)
+                sunxi_pmx_set(pctl->pctl_dev, offset, SUN4I_FUNC_IRQ);
 
         return val;
 }
diff --git a/drivers/pinctrl/sunxi/pinctrl-sunxi.h b/drivers/pinctrl/sunxi/pinctrl-sunxi.h
index 5a51523a3459..e248e81a0f9e 100644
--- a/drivers/pinctrl/sunxi/pinctrl-sunxi.h
+++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.h
@@ -77,6 +77,9 @@
 #define IRQ_LEVEL_LOW           0x03
 #define IRQ_EDGE_BOTH           0x04
 
+#define SUN4I_FUNC_INPUT        0
+#define SUN4I_FUNC_IRQ          6
+
 struct sunxi_desc_function {
         const char      *name;
         u8              muxval;
@@ -94,6 +97,7 @@ struct sunxi_pinctrl_desc {
         int                             npins;
         unsigned                        pin_base;
         unsigned                        irq_banks;
+        bool                            irq_read_needs_mux;
 };
 
 struct sunxi_pinctrl_function {