[PATCH 1/2] mfd: palmas: support IRQ inversion at the board level

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

Some boards or SoCs have an inverter between the PMIC IRQ output pin and
the IRQ controller input signal.

The IRQ specifier in DT is meant to represent the IRQ flags at the input
to the IRQ controller.

The Palmas HW's IRQ output has configurable polarity. The driver
currently selects the output polarity by querying the input polarity at
the IRQ controller. This works fine if the IRQ signal is routed directly
from the PMIC to the IRQ controller with no intervening logic. However,
if the signal is inverted between the two, this automatic polarity
selection gets the wrong answer.

Add an additional optional DT and platform data parameter which indicates
that such an inversion occurs. If this option is enabled, the Palmas
driver will configure its IRQ output to the opposite polarity of the IRQ
controller's input.

An alternative would have been to add a new non-optional DT parameter to
indicate the exact desired output polarity. However, this would have been
an incompatible change to the DT binding.

Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
If this patch could be applied to its own branch (w/ signed tag) in the
MFD tree, that would great; then I can pull patch 1/2 into the Tegra tree
so that I can apply patch 2/2 to the Tegra tree. Thanks.
---
 Documentation/devicetree/bindings/mfd/palmas.txt | 6 ++++++
 drivers/mfd/palmas.c                             | 4 ++++
 include/linux/mfd/palmas.h                       | 1 +
 3 files changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/palmas.txt b/Documentation/devicetree/bindings/mfd/palmas.txt
index e5f0f8303461..76ec509d5f87 100644
--- a/Documentation/devicetree/bindings/mfd/palmas.txt
+++ b/Documentation/devicetree/bindings/mfd/palmas.txt
@@ -18,6 +18,12 @@ Required properties:
   ti,tps659038
 and also the generic series names
   ti,palmas
+- interrupts : Should contain a single entry for the IRQ output.
+- ti,irq-externally-inverted : If missing, the polarity of the Palmas IRQ
+  output should be set to the opposite of the polarity indicated by the IRQ
+  specifier in the interrupts property. If absent, the polarity should be
+  configured to match. This allows the representation of an inverter between
+  the Palmas IRQ output and the interrupt parent's IRQ input.
 - interrupt-controller : palmas has its own internal IRQs
 - #interrupt-cells : should be set to 2 for IRQ number and flags
   The first cell is the IRQ number.
diff --git a/drivers/mfd/palmas.c b/drivers/mfd/palmas.c
index d280d789e55a..f4ea932adf8d 100644
--- a/drivers/mfd/palmas.c
+++ b/drivers/mfd/palmas.c
@@ -293,6 +293,8 @@ static int palmas_set_pdata_irq_flag(struct i2c_client *i2c,
 	}
 
 	pdata->irq_flags = irqd_get_trigger_type(irq_data);
+	pdata->irq_external_inversion = of_property_read_bool(i2c->dev.of_node,
+						"ti,irq-externally-inverted");
 	dev_info(&i2c->dev, "Irq flag is 0x%08x\n", pdata->irq_flags);
 	return 0;
 }
@@ -447,6 +449,8 @@ static int palmas_i2c_probe(struct i2c_client *i2c,
 		reg = PALMAS_POLARITY_CTRL_INT_POLARITY;
 	else
 		reg = 0;
+	if (pdata->irq_external_inversion)
+		reg ^= PALMAS_POLARITY_CTRL_INT_POLARITY;
 	ret = palmas_update_bits(palmas, PALMAS_PU_PD_OD_BASE,
 			PALMAS_POLARITY_CTRL, PALMAS_POLARITY_CTRL_INT_POLARITY,
 			reg);
diff --git a/include/linux/mfd/palmas.h b/include/linux/mfd/palmas.h
index 9974e387e483..2fdf08c50a48 100644
--- a/include/linux/mfd/palmas.h
+++ b/include/linux/mfd/palmas.h
@@ -292,6 +292,7 @@ struct palmas_clk_platform_data {
 
 struct palmas_platform_data {
 	int irq_flags;
+	bool irq_external_inversion;
 	int gpio_base;
 
 	/* bit value to be loaded to the POWER_CTRL register */
-- 
1.8.1.5