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Subject[PATCH v5 2/2] iio: Aspeed ADC
Date
Aspeed BMC SoCs include a 16 channel, 10-bit ADC. Low and high threshold
interrupts are supported by the hardware but are not currently implemented.

Signed-off-by: Rick Altherr <raltherr@google.com>
---

Changes in v5:
- Return EINVAL for unimplemented read/write channel infos.
- Return EPERM for write attempts to read-only channel infos.

Changes in v4:
- Avoid copying per-model data to per-instance data

Changes in v3:
- Drop model numbers from description as same IP is used in every generation
- Remove unused macros
- Shorten macro prefix to just ASPEED_
- Remove extraneous whitespace
- Rename 2nd argument of ASPEED_CHAN() to clarify purpose
- Use existing macros in place of magic constants
- Remove unnecessary logging in failure conditions during probe
- Disable ADC hardware during remove()
- Add a NULL terminator to of_match_table
- Add per-model data to accomodate slight variations (vref, min/max sample rate)
- Added missing Kconfig depends on COMMON_CLK

Changes in v2:
- Rewritten as an IIO device
- Renamed register macros to describe the register's purpose
- Replaced awkward reading of 16-bit data registers with readw()
- Added Kconfig dependency on COMPILE_TEST

drivers/iio/adc/Kconfig | 11 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/aspeed_adc.c | 294 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 306 insertions(+)
create mode 100644 drivers/iio/adc/aspeed_adc.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 2268a6fb9865..236d05f99e80 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -130,6 +130,17 @@ config AD799X
To compile this driver as a module, choose M here: the module will be
called ad799x.

+config ASPEED_ADC
+ tristate "Aspeed ADC"
+ depends on ARCH_ASPEED || COMPILE_TEST
+ depends on COMMON_CLK
+ help
+ If you say yes here you get support for the ADC included in Aspeed
+ BMC SoCs.
+
+ To compile this driver as a module, choose M here: the module will be
+ called aspeed_adc.
+
config AT91_ADC
tristate "Atmel AT91 ADC"
depends on ARCH_AT91
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 73dbe399f894..306f10ffca74 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_AD7791) += ad7791.o
obj-$(CONFIG_AD7793) += ad7793.o
obj-$(CONFIG_AD7887) += ad7887.o
obj-$(CONFIG_AD799X) += ad799x.o
+obj-$(CONFIG_ASPEED_ADC) += aspeed_adc.o
obj-$(CONFIG_AT91_ADC) += at91_adc.o
obj-$(CONFIG_AT91_SAMA5D2_ADC) += at91-sama5d2_adc.o
obj-$(CONFIG_AXP288_ADC) += axp288_adc.o
diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
new file mode 100644
index 000000000000..2283ed202194
--- /dev/null
+++ b/drivers/iio/adc/aspeed_adc.c
@@ -0,0 +1,294 @@
+/*
+ * Aspeed AST2400/2500 ADC
+ *
+ * Copyright (C) 2017 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ */
+
+#include <asm/io.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/driver.h>
+
+#define ASPEED_RESOLUTION_BITS 10
+#define ASPEED_CLOCKS_PER_SAMPLE 12
+
+#define ASPEED_REG_ENGINE_CONTROL 0x00
+#define ASPEED_REG_INTERRUPT_CONTROL 0x04
+#define ASPEED_REG_VGA_DETECT_CONTROL 0x08
+#define ASPEED_REG_CLOCK_CONTROL 0x0C
+#define ASPEED_REG_MAX 0xC0
+
+#define ASPEED_OPERATION_MODE_POWER_DOWN (0x0 << 1)
+#define ASPEED_OPERATION_MODE_STANDBY (0x1 << 1)
+#define ASPEED_OPERATION_MODE_NORMAL (0x7 << 1)
+
+#define ASPEED_ENGINE_ENABLE BIT(0)
+
+struct aspeed_adc_model_data {
+ const char *model_name;
+ unsigned int min_sampling_rate; // Hz
+ unsigned int max_sampling_rate; // Hz
+ unsigned int vref_voltage; // mV
+};
+
+struct aspeed_adc_data {
+ struct device *dev;
+ void __iomem *base;
+ spinlock_t clk_lock;
+ struct clk_hw *clk_prescaler;
+ struct clk_hw *clk_scaler;
+};
+
+#define ASPEED_CHAN(_idx, _data_reg_addr) { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = (_idx), \
+ .address = (_data_reg_addr), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \
+ BIT(IIO_CHAN_INFO_SAMP_FREQ), \
+}
+
+static const struct iio_chan_spec aspeed_adc_iio_channels[] = {
+ ASPEED_CHAN(0, 0x10),
+ ASPEED_CHAN(1, 0x12),
+ ASPEED_CHAN(2, 0x14),
+ ASPEED_CHAN(3, 0x16),
+ ASPEED_CHAN(4, 0x18),
+ ASPEED_CHAN(5, 0x1A),
+ ASPEED_CHAN(6, 0x1C),
+ ASPEED_CHAN(7, 0x1E),
+ ASPEED_CHAN(8, 0x20),
+ ASPEED_CHAN(9, 0x22),
+ ASPEED_CHAN(10, 0x24),
+ ASPEED_CHAN(11, 0x26),
+ ASPEED_CHAN(12, 0x28),
+ ASPEED_CHAN(13, 0x2A),
+ ASPEED_CHAN(14, 0x2C),
+ ASPEED_CHAN(15, 0x2E),
+};
+
+static int aspeed_adc_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct aspeed_adc_data *data = iio_priv(indio_dev);
+ const struct aspeed_adc_model_data *model_data =
+ of_device_get_match_data(data->dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ *val = readw(data->base + chan->address);
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ *val = model_data->vref_voltage;
+ *val2 = ASPEED_RESOLUTION_BITS;
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ *val = clk_get_rate(data->clk_scaler->clk) /
+ ASPEED_CLOCKS_PER_SAMPLE;
+ return IIO_VAL_INT;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static int aspeed_adc_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct aspeed_adc_data *data = iio_priv(indio_dev);
+ const struct aspeed_adc_model_data *model_data =
+ of_device_get_match_data(data->dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ if (val < model_data->min_sampling_rate ||
+ val > model_data->max_sampling_rate)
+ return -EINVAL;
+
+ clk_set_rate(data->clk_scaler->clk,
+ val * ASPEED_CLOCKS_PER_SAMPLE);
+ return 0;
+
+ case IIO_CHAN_INFO_SCALE:
+ case IIO_CHAN_INFO_RAW:
+ /*
+ * Technically, these could be written but the only reasons
+ * for doing so seem better handled in userspace. EPERM is
+ * returned to signal this is a policy choice rather than a
+ * hardware limitation.
+ */
+ return -EPERM;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static int aspeed_adc_reg_access(struct iio_dev *indio_dev,
+ unsigned int reg, unsigned int writeval,
+ unsigned int *readval)
+{
+ struct aspeed_adc_data *data = iio_priv(indio_dev);
+
+ if (!readval || reg % 4 || reg > ASPEED_REG_MAX)
+ return -EINVAL;
+
+ *readval = readl(data->base + reg);
+ return 0;
+}
+
+static const struct iio_info aspeed_adc_iio_info = {
+ .driver_module = THIS_MODULE,
+ .read_raw = aspeed_adc_read_raw,
+ .write_raw = aspeed_adc_write_raw,
+ .debugfs_reg_access = aspeed_adc_reg_access,
+};
+
+static int aspeed_adc_probe(struct platform_device *pdev)
+{
+ struct iio_dev *indio_dev;
+ struct aspeed_adc_data *data;
+ const struct aspeed_adc_model_data *model_data;
+ struct resource *res;
+ const char *clk_parent_name;
+ int ret;
+ u32 adc_engine_control_reg_val;
+
+ indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+ data->dev = &pdev->dev;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ data->base = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(data->base))
+ return PTR_ERR(data->base);
+
+ /* Register ADC clock prescaler with source specified by device tree. */
+ spin_lock_init(&data->clk_lock);
+ clk_parent_name = of_clk_get_parent_name(pdev->dev.of_node, 0);
+
+ data->clk_prescaler = clk_hw_register_divider(
+ &pdev->dev, "prescaler", clk_parent_name, 0,
+ data->base + ASPEED_REG_CLOCK_CONTROL,
+ 17, 15, 0, &data->clk_lock);
+ if (IS_ERR(data->clk_prescaler))
+ return PTR_ERR(data->clk_prescaler);
+
+ /*
+ * Register ADC clock scaler downstream from the prescaler. Allow rate
+ * setting to adjust the prescaler as well.
+ */
+ data->clk_scaler = clk_hw_register_divider(
+ &pdev->dev, "scaler", "prescaler",
+ CLK_SET_RATE_PARENT,
+ data->base + ASPEED_REG_CLOCK_CONTROL,
+ 0, 10, 0, &data->clk_lock);
+ if (IS_ERR(data->clk_scaler)) {
+ ret = PTR_ERR(data->clk_scaler);
+ goto scaler_error;
+ }
+
+ /* Start all channels in normal mode. */
+ clk_prepare_enable(data->clk_scaler->clk);
+ adc_engine_control_reg_val = GENMASK(31, 16) |
+ ASPEED_OPERATION_MODE_NORMAL | ASPEED_ENGINE_ENABLE;
+ writel(adc_engine_control_reg_val,
+ data->base + ASPEED_REG_ENGINE_CONTROL);
+
+ model_data = of_device_get_match_data(&pdev->dev);
+ indio_dev->name = model_data->model_name;
+ indio_dev->dev.parent = &pdev->dev;
+ indio_dev->info = &aspeed_adc_iio_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = aspeed_adc_iio_channels;
+ indio_dev->num_channels = ARRAY_SIZE(aspeed_adc_iio_channels);
+
+ ret = iio_device_register(indio_dev);
+ if (ret)
+ goto iio_register_error;
+
+ return 0;
+
+iio_register_error:
+ writel(ASPEED_OPERATION_MODE_POWER_DOWN,
+ data->base + ASPEED_REG_ENGINE_CONTROL);
+ clk_disable_unprepare(data->clk_scaler->clk);
+ clk_hw_unregister_divider(data->clk_scaler);
+
+scaler_error:
+ clk_hw_unregister_divider(data->clk_prescaler);
+ return ret;
+}
+
+static int aspeed_adc_remove(struct platform_device *pdev)
+{
+ struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+ struct aspeed_adc_data *data = iio_priv(indio_dev);
+
+ iio_device_unregister(indio_dev);
+ writel(ASPEED_OPERATION_MODE_POWER_DOWN,
+ data->base + ASPEED_REG_ENGINE_CONTROL);
+ clk_disable_unprepare(data->clk_scaler->clk);
+ clk_hw_unregister_divider(data->clk_scaler);
+ clk_hw_unregister_divider(data->clk_prescaler);
+
+ return 0;
+}
+
+static const struct aspeed_adc_model_data ast2400_model_data = {
+ .model_name = "ast2400-adc",
+ .vref_voltage = 2500, // mV
+ .min_sampling_rate = 10000,
+ .max_sampling_rate = 500000,
+};
+
+static const struct aspeed_adc_model_data ast2500_model_data = {
+ .model_name = "ast2500-adc",
+ .vref_voltage = 1800, // mV
+ .min_sampling_rate = 1,
+ .max_sampling_rate = 1000000,
+};
+
+static const struct of_device_id aspeed_adc_matches[] = {
+ { .compatible = "aspeed,ast2400-adc", .data = &ast2400_model_data },
+ { .compatible = "aspeed,ast2500-adc", .data = &ast2500_model_data },
+ {},
+};
+MODULE_DEVICE_TABLE(of, aspeed_adc_matches);
+
+static struct platform_driver aspeed_adc_driver = {
+ .probe = aspeed_adc_probe,
+ .remove = aspeed_adc_remove,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = aspeed_adc_matches,
+ }
+};
+
+module_platform_driver(aspeed_adc_driver);
+
+MODULE_AUTHOR("Rick Altherr <raltherr@google.com>");
+MODULE_DESCRIPTION("Aspeed AST2400/2500 ADC Driver");
+MODULE_LICENSE("GPL");
--
2.12.2.564.g063fe858b8-goog
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