Re: [PATCH v2 2/2] iio: Aspeed AST2400/AST2500 ADC

From: Rick Altherr
Date: Thu Mar 23 2017 - 12:54:20 EST

Restoring the list after an accidental direct reply.

On Wed, Mar 22, 2017 at 1:30 PM, Rick Altherr <raltherr@xxxxxxxxxx> wrote:
> On Tue, Mar 21, 2017 at 2:14 PM, Peter Meerwald-Stadler
> <pmeerw@xxxxxxxxxx> wrote:
>>
>>> Aspeed AST2400/AST2500 BMC SoCs include a 16 channel, 10-bit ADC. Low
>>> and high threshold interrupts are supported by the hardware but are not
>>> currently implemented.
>>
>> comments below
>> link to a datasheet would be nice
>>
>
> No public datasheet is available. I've tried.
>
>>> Signed-off-by: Rick Altherr <raltherr@xxxxxxxxxx>
>>> ---
>>>
>>> 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 | 10 ++
>>> drivers/iio/adc/Makefile | 1 +
>>> drivers/iio/adc/aspeed_adc.c | 271 +++++++++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 282 insertions(+)
>>> create mode 100644 drivers/iio/adc/aspeed_adc.c
>>>
>>> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
>>> index 2268a6fb9865..9672d799a3fb 100644
>>> --- a/drivers/iio/adc/Kconfig
>>> +++ b/drivers/iio/adc/Kconfig
>>> @@ -130,6 +130,16 @@ config AD799X
>>> To compile this driver as a module, choose M here: the module will be
>>> called ad799x.
>>>
>>> +config ASPEED_ADC
>>> + tristate "Aspeed AST2400/AST2500 ADC"
>>> + depends on ARCH_ASPEED || COMPILE_TEST
>>> + help
>>> + If you say yes here you get support for the Aspeed AST2400/AST2500
>>> + ADC.
>>> +
>>> + 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..9220909aefd4
>>> --- /dev/null
>>> +++ b/drivers/iio/adc/aspeed_adc.c
>>> @@ -0,0 +1,271 @@
>>> +/*
>>> + * 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_ADC_NUM_CHANNELS 16
>>
>> _NUM_CHANNELS is not used, remove
>
> Ack
>
>>
>>> +#define ASPEED_ADC_REF_VOLTAGE 2500 /* millivolts */
>>
>> should be used below
>
> Ack
>
>>
>>> +#define ASPEED_ADC_RESOLUTION_BITS 10
>>
>> should be used below
>
> Ack
>
>>
>>> +#define ASPEED_ADC_MIN_SAMP_RATE 10000
>>> +#define ASPEED_ADC_MAX_SAMP_RATE 500000
>>> +#define ASPEED_ADC_CLOCKS_PER_SAMPLE 12
>>> +
>>> +#define ASPEED_ADC_REG_ENGINE_CONTROL 0x00
>>> +#define ASPEED_ADC_REG_INTERRUPT_CONTROL 0x04
>>> +#define ASPEED_ADC_REG_VGA_DETECT_CONTROL 0x08
>>> +#define ASPEED_ADC_REG_CLOCK_CONTROL 0x0C
>>> +#define ASPEED_ADC_REG_MAX 0xC0
>>> +
>>> +#define ASPEED_ADC_OPERATION_MODE_POWER_DOWN (0x0 << 1)
>>> +#define ASPEED_ADC_OPERATION_MODE_STANDBY (0x1 << 1)
>>> +#define ASPEED_ADC_OPERATION_MODE_NORMAL (0x7 << 1)
>>> +
>>> +#define ASPEED_ADC_ENGINE_ENABLE BIT(0)
>>> +
>>> +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_ADC_CHAN(_idx, _addr) { \
>>> + .type = IIO_VOLTAGE, \
>>> + .indexed = 1, \
>>> + .channel = (_idx), \
>>> + .address = (_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_ADC_CHAN(0, 0x10),
>>> + ASPEED_ADC_CHAN(1, 0x12),
>>> + ASPEED_ADC_CHAN(2, 0x14),
>>> + ASPEED_ADC_CHAN(3, 0x16),
>>> + ASPEED_ADC_CHAN(4, 0x18),
>>> + ASPEED_ADC_CHAN(5, 0x1A),
>>> + ASPEED_ADC_CHAN(6, 0x1C),
>>> + ASPEED_ADC_CHAN(7, 0x1E),
>>> + ASPEED_ADC_CHAN(8, 0x20),
>>> + ASPEED_ADC_CHAN(9, 0x22),
>>> + ASPEED_ADC_CHAN(10, 0x24),
>>> + ASPEED_ADC_CHAN(11, 0x26),
>>> + ASPEED_ADC_CHAN(12, 0x28),
>>> + ASPEED_ADC_CHAN(13, 0x2A),
>>> + ASPEED_ADC_CHAN(14, 0x2C),
>>> + ASPEED_ADC_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);
>>> +
>>> + switch (mask) {
>>> + case IIO_CHAN_INFO_RAW:
>>> + *val = readw(data->base + chan->address);
>>> + return IIO_VAL_INT;
>>> +
>>> + case IIO_CHAN_INFO_SCALE:
>>> + *val = 2500; // mV
>>
>> REF_VOLTAGE?
>
> Ack
>
>>
>>> + *val2 = 10;
>>> + return IIO_VAL_FRACTIONAL_LOG2;
>>> +
>>> + case IIO_CHAN_INFO_SAMP_FREQ:
>>> + *val = clk_get_rate(data->clk_scaler->clk) /
>>> + ASPEED_ADC_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);
>>> +
>>> + switch (mask) {
>>> + case IIO_CHAN_INFO_SAMP_FREQ:
>>> + if (val < ASPEED_ADC_MIN_SAMP_RATE ||
>>> + val > ASPEED_ADC_MAX_SAMP_RATE)
>>> + return -EINVAL;
>>> +
>>> + clk_set_rate(data->clk_scaler->clk,
>>> + val * ASPEED_ADC_CLOCKS_PER_SAMPLE);
>>> + return 0;
>>> +
>>> + 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_ADC_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,
>>
>> without & (matter of taste)
>
> Ack
>
>>
>>> + .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;
>>> + 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) {
>>> + dev_err(&pdev->dev, "Failed allocating iio device\n");
>>> + return -ENOMEM;
>>> + }
>>> +
>>> + data = iio_priv(indio_dev);
>>> +
>>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>> + data->base = devm_ioremap_resource(&pdev->dev, res);
>>> + if (IS_ERR(data->base)) {
>>> + dev_err(&pdev->dev, "Failed allocating device resources\n");
>>> + ret = PTR_ERR(data->base);
>>> + goto resource_error;
>>
>> just return here?
>
> Ack
>
>>
>>> + }
>>> +
>>> + /* 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_ADC_REG_CLOCK_CONTROL,
>>> + 17, 15, 0, &data->clk_lock);
>>> + if (IS_ERR(data->clk_prescaler)) {
>>> + dev_err(&pdev->dev, "Failed allocating prescaler clock\n");
>>> + ret = PTR_ERR(data->clk_prescaler);
>>> + goto prescaler_error;
>>
>> just return here?
>
> Ack
>
>>
>>> + }
>>> +
>>> + /*
>>> + * 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_ADC_REG_CLOCK_CONTROL,
>>> + 0, 10, 0, &data->clk_lock);
>>> + if (IS_ERR(data->clk_scaler)) {
>>> + dev_err(&pdev->dev, "Failed allocating scaler clock\n");
>>> + 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_ADC_OPERATION_MODE_NORMAL | ASPEED_ADC_ENGINE_ENABLE;
>>> + writel(adc_engine_control_reg_val,
>>> + data->base + ASPEED_ADC_REG_ENGINE_CONTROL);
>>> +
>>> + indio_dev->name = dev_name(&pdev->dev);
>>> + 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) {
>>> + dev_err(&pdev->dev, "Could't register the device.\n");
>>
>> Couldn't
>
> Ack
>
>>
>>> + goto iio_register_error;
>>> + }
>>> +
>>> + return 0;
>>> +
>>> +iio_register_error:
>>> + writel(0x0, data->base + ASPEED_ADC_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);
>>> +
>>> +prescaler_error:
>>> +resource_error:
>>> + 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(0x0, data->base + ASPEED_ADC_REG_ENGINE_CONTROL);
>> I guess this power off the device?
>
> Yes. You're right that it makes sense to do that during removal as well.
>
>>
>> the MODE #defines are now used (powerdown, normal, etc.)
>
> NORMAL is used in probe(). I'll use powerdown here.
>
>>
>>> + clk_disable_unprepare(data->clk_scaler->clk);
>>> + clk_hw_unregister_divider(data->clk_scaler);
>>> + clk_hw_unregister_divider(data->clk_prescaler);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +const struct of_device_id aspeed_adc_matches[] = {
>>> + { .compatible = "aspeed,ast2400-adc" },
>>> + { .compatible = "aspeed,ast2500-adc" },
>>> +};
>>> +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");
>>>
>>
>> --
>>
>> Peter Meerwald-Stadler
>> Mobile: +43 664 24 44 418