mfd: qcom-spmi-pmic: add support for slow SPMI busses

Add device tree support for configuring if mutexes or spinlocks
should be used in the regmap configuration (i.e. the fast_io
element value).  This ensures that qcom-spmi-pmic slave devices
can be used with SPMI busses that must operate in process
context.

Change-Id: I3abdee36935457db497ce6ff2a242755fc3aff90
Signed-off-by: David Collins <collinsd@codeaurora.org>

Documentation/devicetree/bindings/mfd/qcom,spmi-pmic.txt

@@ -42,6 +42,8 @@ Optional properties for peripheral child nodes:
                    see:
                    Documentation/devicetree/bindings/spmi/qcom,spmi-pmic-arb.txt
 - interrupt-names: Corresponding interrupt name to the interrupts property
+- qcom,can-sleep:  Boolean flag indicating that processes waiting on SPMI
+		   transactions may sleep
 
 Each child node of SPMI slave id represents a function of the PMIC. In the
 example below the rtc device node represents a peripheral of pm8941

drivers/mfd/qcom-spmi-pmic.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2015, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2014-2015, 2017, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -118,12 +118,23 @@ static const struct regmap_config spmi_regmap_config = {
 	.fast_io	= true,
 };
 
+static const struct regmap_config spmi_regmap_can_sleep_config = {
+	.reg_bits	= 16,
+	.val_bits	= 8,
+	.max_register	= 0xffff,
+	.fast_io	= false,
+};
+
 static int pmic_spmi_probe(struct spmi_device *sdev)
 {
 	struct device_node *root = sdev->dev.of_node;
 	struct regmap *regmap;
 
-	regmap = devm_regmap_init_spmi_ext(sdev, &spmi_regmap_config);
+	if (of_property_read_bool(root, "qcom,can-sleep"))
+		regmap = devm_regmap_init_spmi_ext(sdev,
+						&spmi_regmap_can_sleep_config);
+	else
+		regmap = devm_regmap_init_spmi_ext(sdev, &spmi_regmap_config);
 	if (IS_ERR(regmap))
 		return PTR_ERR(regmap);