Re: [PATCH v5 2/2] iio: Aspeed ADC

[Joel Stanley]

On Wed, Mar 29, 2017 at 8:22 AM, Rick Altherr <raltherr@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>

Reviewed-by: Joel Stanley <joel@xxxxxxxxx>

> ---
>
> 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@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Aspeed AST2400/2500 ADC Driver");
> +MODULE_LICENSE("GPL");
> --
> 2.12.2.564.g063fe858b8-goog
>