[PATCH v3 2/3] ARM: qcom: Add coincell charger driver

[Tim Bird <tim.bird@sonymobile.com>]

This driver is used to configure the coincell charger found in
Qualcomm PMICs.

The driver allows configuring the current-limiting resistor for
the charger, as well as the voltage to apply to the coincell
(or capacitor) when charging.

Signed-off-by: Tim Bird <tim.bird@sonymobile.com>
---

Changes in v3:
 - change 'depends on' in Kconfig 
 - remove 'select REGMAP' in Kconfig
 - put spaces in map lists
 - use 'bool' type for enable variable
 - remove some printks
 - add missing braces in error handling in qcom_coincell_chgr_config
 - eliminate of_node NULL check in probe routine
 - rename driver to qcom-spmi-coincell
 - put struct qcom_coincell on stack, instead of allocating it
 - return the result of a function directly (in a few places)
 - reorder operations to avoid partial register update

 drivers/misc/Kconfig         |  10 +++
 drivers/misc/Makefile        |   1 +
 drivers/misc/qcom-coincell.c | 152 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 163 insertions(+)
 create mode 100644 drivers/misc/qcom-coincell.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 42c3852..ccccc29 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -271,6 +271,16 @@ config HP_ILO
 	  To compile this driver as a module, choose M here: the
 	  module will be called hpilo.
 
+config QCOM_COINCELL
+	tristate "Qualcomm coincell charger support"
+	depends on MFD_SPMI_PMIC || COMPILE_TEST
+	help
+	  This driver supports the coincell block found inside of
+	  Qualcomm PMICs.  The coincell charger provides a means to
+	  charge a coincell battery or backup capacitor which is used
+	  to maintain PMIC register and RTC state in the absence of
+	  external power.
+
 config SGI_GRU
 	tristate "SGI GRU driver"
 	depends on X86_UV && SMP
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index d056fb7..537d7f3 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_LKDTM)		+= lkdtm.o
 obj-$(CONFIG_TIFM_CORE)       	+= tifm_core.o
 obj-$(CONFIG_TIFM_7XX1)       	+= tifm_7xx1.o
 obj-$(CONFIG_PHANTOM)		+= phantom.o
+obj-$(CONFIG_QCOM_COINCELL)	+= qcom-coincell.o
 obj-$(CONFIG_SENSORS_BH1780)	+= bh1780gli.o
 obj-$(CONFIG_SENSORS_BH1770)	+= bh1770glc.o
 obj-$(CONFIG_SENSORS_APDS990X)	+= apds990x.o
diff --git a/drivers/misc/qcom-coincell.c b/drivers/misc/qcom-coincell.c
new file mode 100644
index 0000000..7b4a2da
--- /dev/null
+++ b/drivers/misc/qcom-coincell.c
@@ -0,0 +1,152 @@
+/* Copyright (c) 2013, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2015, Sony Mobile Communications Inc.
+ *
+ * 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
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+
+struct qcom_coincell {
+	struct device	*dev;
+	struct regmap	*regmap;
+	u32		base_addr;
+};
+
+#define QCOM_COINCELL_REG_RSET		0x44
+#define QCOM_COINCELL_REG_VSET		0x45
+#define QCOM_COINCELL_REG_ENABLE	0x46
+
+#define QCOM_COINCELL_ENABLE		BIT(7)
+
+static const int qcom_rset_map[] = { 2100, 1700, 1200, 800 };
+static const int qcom_vset_map[] = { 2500, 3200, 3100, 3000 };
+/* NOTE: for pm8921 and others, voltage of 2500 is 16 (10000b), not 0 */
+
+/* if enable==0, rset and vset are ignored */
+static int qcom_coincell_chgr_config(struct qcom_coincell *chgr, int rset,
+				     int vset, bool enable)
+{
+	int i, j, rc;
+
+	/* if disabling, just do that and skip other operations */
+	if (!enable)
+		return regmap_write(chgr->regmap,
+			  chgr->base_addr + QCOM_COINCELL_REG_ENABLE, 0);
+
+	/* find index for current-limiting resistor */
+	for (i = 0; i < ARRAY_SIZE(qcom_rset_map); i++)
+		if (rset == qcom_rset_map[i])
+			break;
+
+	if (i >= ARRAY_SIZE(qcom_rset_map)) {
+		dev_err(chgr->dev, "invalid rset-ohms value %d\n", rset);
+		return -EINVAL;
+	}
+
+	/* find index for charge voltage */
+	for (j = 0; j < ARRAY_SIZE(qcom_vset_map); j++)
+		if (vset == qcom_vset_map[j])
+			break;
+
+	if (j >= ARRAY_SIZE(qcom_vset_map)) {
+		dev_err(chgr->dev, "invalid vset-millivolts value %d\n", vset);
+		return -EINVAL;
+	}
+
+	rc = regmap_write(chgr->regmap,
+			  chgr->base_addr + QCOM_COINCELL_REG_RSET, i);
+	if (rc) {
+		/*
+		 * This is mainly to flag a bad base_addr (reg) from dts.
+		 * Other failures writing to the registers should be
+		 * extremely rare, or indicative of problems that
+		 * should be reported elsewhere (eg. spmi failure).
+		 */
+		dev_err(chgr->dev, "could not write to RSET register\n");
+		return rc;
+	}
+
+	rc = regmap_write(chgr->regmap,
+		chgr->base_addr + QCOM_COINCELL_REG_VSET, j);
+	if (rc)
+		return rc;
+
+	/* set 'enable' register */
+	return regmap_write(chgr->regmap,
+			    chgr->base_addr + QCOM_COINCELL_REG_ENABLE,
+			    QCOM_COINCELL_ENABLE);
+}
+
+static int qcom_coincell_probe(struct platform_device *pdev)
+{
+	struct device_node *node = pdev->dev.of_node;
+	struct qcom_coincell chgr;
+	u32 rset, vset;
+	bool enable;
+	int rc;
+
+	chgr.dev = &pdev->dev;
+
+	chgr.regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!chgr.regmap) {
+		dev_err(chgr.dev, "Unable to get regmap\n");
+		return -EINVAL;
+	}
+
+	rc = of_property_read_u32(node, "reg", &chgr.base_addr);
+	if (rc)
+		return rc;
+
+	enable = !of_property_read_bool(node, "qcom,charger-disable");
+
+	if (enable) {
+		rc = of_property_read_u32(node, "qcom,rset-ohms", &rset);
+		if (rc) {
+			dev_err(chgr.dev,
+				"can't find 'qcom,rset-ohms' in DT block");
+			return rc;
+		}
+
+		rc = of_property_read_u32(node, "qcom,vset-millivolts", &vset);
+		if (rc) {
+			dev_err(chgr.dev,
+			    "can't find 'qcom,vset-millivolts' in DT block");
+			return rc;
+		}
+	}
+
+	return qcom_coincell_chgr_config(&chgr, rset, vset, enable);
+}
+
+static const struct of_device_id qcom_coincell_match_table[] = {
+	{ .compatible = "qcom,pm8941-coincell", },
+	{}
+};
+
+MODULE_DEVICE_TABLE(of, qcom_coincell_match_table);
+
+static struct platform_driver qcom_coincell_driver = {
+	.driver	= {
+		.name		= "qcom-spmi-coincell",
+		.of_match_table	= qcom_coincell_match_table,
+	},
+	.probe		= qcom_coincell_probe,
+};
+
+module_platform_driver(qcom_coincell_driver);
+
+MODULE_DESCRIPTION("Qualcomm PMIC coincell charger driver");
+MODULE_LICENSE("GPL v2");
-- 
1.8.2.2