ARM: qcom: Add coincell charger driver

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>
Reviewed-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 152 insertions, 0 deletions

diff --git a/drivers/misc/qcom-coincell.c b/drivers/misc/qcom-coincell.c
new file mode 100644
index 000000000000..7b4a2da487a5
--- /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");