[PATCH v6 6/8] platform/mellanox: Introduce support for Mellanox register access driver

From: Vadim Pasternak
Date: Sun Jun 17 2018 - 11:21:28 EST

Introduce new Mellanox platform driver to allow access to Mellanox
programmable device register space trough sysfs interface.
The driver purpose is to provide sysfs interface for user space for the
registers essential for system control and monitoring.
The sets of registers for sysfs access are supposed to be defined per
system type bases and include the registers related to system resets
operation, system reset causes monitoring and some kinds of mux selection.

Signed-off-by: Vadim Pasternak <vadimp@xxxxxxxxxxxx>
---
v5-v6:
Comments pointed out by Darren:
- Fix "filed" to "field" and "form" to "from".
- Drop redundant case for "full register" kind of attribute.
Since regmap_config structure includes the field with the number of
bits in a register address, it protects register from reading/writing
above this limit.
- Use len parameter, received from the user space in kstrtou32 to prevent
reading beyond the end of input buffer.
- Move comment to correct location in mlxreg_io_attr_store routine.
- Provide regval reading operation into a static local function.
v4-v5:
Comments pointed out by Darren:
- Add more comments.
- Add validation for the buffer length in attribute store method.
- Remove unnecessary check for input value in attribute store method.
- Change name val to input_value in order to improve code readability.
Changes added by Vadim:
- Extend logic in attribute show and store methods to cover all
configurations.
v2->v3:
Comments pointed out by Darren:
- Remove conditional assignment per attribute mode type, because mode
will guard against not permitted access.
Verified by Vadim.
v1->v2:
Change added by Vadim:
- Change ---help--- to help in Kconfig, according to new requirements;
---
drivers/platform/mellanox/Kconfig | 11 ++
drivers/platform/mellanox/Makefile | 1 +
drivers/platform/mellanox/mlxreg-io.c | 245 ++++++++++++++++++++++++++++++++++
3 files changed, 257 insertions(+)
create mode 100644 drivers/platform/mellanox/mlxreg-io.c

diff --git a/drivers/platform/mellanox/Kconfig b/drivers/platform/mellanox/Kconfig
index 591bccd..ddfae9fc 100644
--- a/drivers/platform/mellanox/Kconfig
+++ b/drivers/platform/mellanox/Kconfig
@@ -23,4 +23,15 @@ config MLXREG_HOTPLUG
This driver handles hot-plug events for the power suppliers, power
cables and fans on the wide range Mellanox IB and Ethernet systems.

+config MLXREG_IO
+ tristate "Mellanox platform register access driver support"
+ depends on REGMAP
+ depends on HWMON
+ help
+ This driver allows access to Mellanox programmable device register
+ space trough sysfs interface. The sets of registers for sysfs access
+ are defined per system type bases and includes the registers related
+ to system resets operation, system reset causes monitoring and some
+ kinds of mux selection.
+
endif # MELLANOX_PLATFORM
diff --git a/drivers/platform/mellanox/Makefile b/drivers/platform/mellanox/Makefile
index 7c8385e..57074d9c 100644
--- a/drivers/platform/mellanox/Makefile
+++ b/drivers/platform/mellanox/Makefile
@@ -4,3 +4,4 @@
# Mellanox Platform-Specific Drivers
#
obj-$(CONFIG_MLXREG_HOTPLUG) += mlxreg-hotplug.o
+obj-$(CONFIG_MLXREG_IO) += mlxreg-io.o
diff --git a/drivers/platform/mellanox/mlxreg-io.c b/drivers/platform/mellanox/mlxreg-io.c
new file mode 100644
index 0000000..c192dfe
--- /dev/null
+++ b/drivers/platform/mellanox/mlxreg-io.c
@@ -0,0 +1,245 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Mellanox register access driver
+ *
+ * Copyright (C) 2018 Mellanox Technologies
+ * Copyright (C) 2018 Vadim Pasternak <vadimp@xxxxxxxxxxxx>
+ */
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_data/mlxreg.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+/* Attribute parameters. */
+#define MLXREG_IO_ATT_SIZE 10
+#define MLXREG_IO_ATT_NUM 48
+
+/**
+ * struct mlxreg_io_priv_data - driver's private data:
+ *
+ * @pdev: platform device;
+ * @pdata: platform data;
+ * @hwmon: hwmon device;
+ * @mlxreg_io_attr: sysfs attributes array;
+ * @mlxreg_io_dev_attr: sysfs sensor device attribute array;
+ * @group: sysfs attribute group;
+ * @groups: list of sysfs attribute group for hwmon registration;
+ */
+struct mlxreg_io_priv_data {
+ struct platform_device *pdev;
+ struct mlxreg_core_platform_data *pdata;
+ struct device *hwmon;
+ struct attribute *mlxreg_io_attr[MLXREG_IO_ATT_NUM + 1];
+ struct sensor_device_attribute mlxreg_io_dev_attr[MLXREG_IO_ATT_NUM];
+ struct attribute_group group;
+ const struct attribute_group *groups[2];
+};
+
+static int
+mlxreg_io_get_reg(void *regmap, struct mlxreg_core_data *data, u32 in_val,
+ bool rw_flag, u32 *regval)
+{
+ int ret;
+
+ ret = regmap_read(regmap, data->reg, regval);
+ if (ret)
+ goto access_error;
+
+ /*
+ * There are three kinds of attributes: single bit, full register's
+ * bits and bit sequence. For the first kind field mask indicates which
+ * bits are not related and field bit is set zero. For the second kind
+ * field mask is set to zero and field bit is set with all bits one.
+ * No special handling for such kind of attributes - pass value as is.
+ * For the third kind, field mask indicates which bits are related and
+ * field bit is set to the first bit number (from 1 to 32) is the bit
+ * sequence.
+ */
+ if (!data->bit) {
+ /* Single bit. */
+ if (rw_flag) {
+ /* For show: expose effective bit value as 0 or 1. */
+ *regval = !!(*regval & ~data->mask);
+ } else {
+ /* For store: set effective bit value. */
+ *regval &= data->mask;
+ if (in_val)
+ *regval |= ~data->mask;
+ }
+ } else if (data->mask) {
+ /* Bit sequence. */
+ if (rw_flag) {
+ /* For show: mask and shift right. */
+ *regval = ror32(*regval & data->mask, (data->bit - 1));
+ } else {
+ /* For store: shift to the position and mask. */
+ in_val = rol32(in_val, data->bit - 1) & data->mask;
+ /* Clear relevant bits and set them to new value. */
+ *regval = (*regval & ~data->mask) | in_val;
+ }
+ }
+
+access_error:
+ return ret;
+}
+
+static ssize_t
+mlxreg_io_attr_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct mlxreg_io_priv_data *priv = dev_get_drvdata(dev);
+ int index = to_sensor_dev_attr(attr)->index;
+ struct mlxreg_core_data *data = priv->pdata->data + index;
+ u32 regval = 0;
+ int ret;
+
+ ret = mlxreg_io_get_reg(priv->pdata->regmap, data, 0, true, &regval);
+ if (ret)
+ goto access_error;
+
+ return sprintf(buf, "%u\n", regval);
+
+access_error:
+ return ret;
+}
+
+static ssize_t
+mlxreg_io_attr_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct mlxreg_io_priv_data *priv = dev_get_drvdata(dev);
+ int index = to_sensor_dev_attr(attr)->index;
+ struct mlxreg_core_data *data = priv->pdata->data + index;
+ u32 input_val, regval;
+ int ret;
+
+ if (len > MLXREG_IO_ATT_SIZE)
+ return -EINVAL;
+
+ /* Convert buffer to input value. */
+ ret = kstrtou32(buf, len, &input_val);
+ if (ret)
+ return ret;
+
+ ret = mlxreg_io_get_reg(priv->pdata->regmap, data, input_val, false,
+ &regval);
+ if (ret)
+ goto access_error;
+
+ ret = regmap_write(priv->pdata->regmap, data->reg, regval);
+ if (ret)
+ goto access_error;
+
+ return len;
+
+access_error:
+ dev_err(&priv->pdev->dev, "Bus access error\n");
+ return ret;
+}
+
+static struct device_attribute mlxreg_io_devattr_rw = {
+ .show = mlxreg_io_attr_show,
+ .store = mlxreg_io_attr_store,
+};
+
+static int mlxreg_io_attr_init(struct mlxreg_io_priv_data *priv)
+{
+ int i;
+
+ priv->group.attrs = devm_kzalloc(&priv->pdev->dev,
+ priv->pdata->counter *
+ sizeof(struct attribute *),
+ GFP_KERNEL);
+ if (!priv->group.attrs)
+ return -ENOMEM;
+
+ for (i = 0; i < priv->pdata->counter; i++) {
+ priv->mlxreg_io_attr[i] =
+ &priv->mlxreg_io_dev_attr[i].dev_attr.attr;
+ memcpy(&priv->mlxreg_io_dev_attr[i].dev_attr,
+ &mlxreg_io_devattr_rw, sizeof(struct device_attribute));
+
+ /* Set attribute name as a label. */
+ priv->mlxreg_io_attr[i]->name =
+ devm_kasprintf(&priv->pdev->dev, GFP_KERNEL,
+ priv->pdata->data[i].label);
+
+ if (!priv->mlxreg_io_attr[i]->name) {
+ dev_err(&priv->pdev->dev, "Memory allocation failed for sysfs attribute %d.\n",
+ i + 1);
+ return -ENOMEM;
+ }
+
+ priv->mlxreg_io_dev_attr[i].dev_attr.attr.mode =
+ priv->pdata->data[i].mode;
+ priv->mlxreg_io_dev_attr[i].dev_attr.attr.name =
+ priv->mlxreg_io_attr[i]->name;
+ priv->mlxreg_io_dev_attr[i].index = i;
+ sysfs_attr_init(&priv->mlxreg_io_dev_attr[i].dev_attr.attr);
+ }
+
+ priv->group.attrs = priv->mlxreg_io_attr;
+ priv->groups[0] = &priv->group;
+ priv->groups[1] = NULL;
+
+ return 0;
+}
+
+static int mlxreg_io_probe(struct platform_device *pdev)
+{
+ struct mlxreg_io_priv_data *priv;
+ int err;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->pdata = dev_get_platdata(&pdev->dev);
+ if (!priv->pdata) {
+ dev_err(&pdev->dev, "Failed to get platform data.\n");
+ return -EINVAL;
+ }
+
+ priv->pdev = pdev;
+
+ err = mlxreg_io_attr_init(priv);
+ if (err) {
+ dev_err(&priv->pdev->dev, "Failed to allocate attributes: %d\n",
+ err);
+ return err;
+ }
+
+ priv->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
+ "mlxreg_io",
+ priv,
+ priv->groups);
+ if (IS_ERR(priv->hwmon)) {
+ dev_err(&pdev->dev, "Failed to register hwmon device %ld\n",
+ PTR_ERR(priv->hwmon));
+ return PTR_ERR(priv->hwmon);
+ }
+
+ dev_set_drvdata(&pdev->dev, priv);
+
+ return 0;
+}
+
+static struct platform_driver mlxreg_io_driver = {
+ .driver = {
+ .name = "mlxreg-io",
+ },
+ .probe = mlxreg_io_probe,
+};
+
+module_platform_driver(mlxreg_io_driver);
+
+MODULE_AUTHOR("Vadim Pasternak <vadimp@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Mellanox regmap I/O access driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:mlxreg-io");
--
2.1.4