[PATCH v2 2/2] iio: Aspeed AST2400/AST2500 ADC
Jonathan Cameron
jic23 at kernel.org
Sun Mar 26 04:20:31 AEDT 2017
On 22/03/17 09:47, Joel Stanley wrote:
> On Wed, Mar 22, 2017 at 7:18 AM, Rick Altherr <raltherr at google.com> 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.
>>
>> Signed-off-by: Rick Altherr <raltherr at google.com>
>
> Looks good Rick. I gave it a review from the perspective of the Aspeed
> soc. I also gave it a spin on the Aspeed AST2500 EVB which mostly
> worked, but uncovered some things that need addressing.
Few follow ups inline... Busy week so I'm playing catch up on this.
>
> My device tree additions looked like this:
>
> adc: adc at 1e6e9000 {
> compatible = "aspeed,ast2500-adc";
> reg = <0x1e6e9000 0xb0>;
> clocks = <&clk_apb>;
> #io-channel-cells = <1>;
>
> pinctrl-names = "default";
> pinctrl-0 = <&pinctrl_adc0_default>;
> };
>
> iio-hwmon {
> compatible = "iio-hwmon";
> io-channels = <&adc 0>;
> };
>
> I got this output from lm-sensors when booted:
>
> iio_hwmon-isa-0000
> Adapter: ISA adapter
> in1: +1.28 V
>
> I then wired up ADC0 to ADC_12V_TW on the EVB. The above changed to:
>
> iio_hwmon-isa-0000
> Adapter: ISA adapter
> in1: +1.80 V
>
> ADC_12V_TW is the 12V rail sampled through a voltage divider. The
> voltage should be: 12 * 680 / ( 5600 + 680) = 1.299
>
> cat /sys/bus/iio/devices/iio:device0/in_voltage1_raw
> 738
>
> 738 / 1023 * 1.8 = 1.2975
>
> Looks like the first channel is working! However our reference is
> incorrect. Your driver has ASPEED_ADC_REF_VOLTAGE but doesn't use it.
> It does hardcode 2500 in the aspeed_adc_read_raw callback:
>
> case IIO_CHAN_INFO_SCALE:
> *val = 2500; // mV
> *val2 = 10;
> return IIO_VAL_FRACTIONAL_LOG2;
>
> Should this value the the constant you define?
>
> Regardless, I don't think the reference voltage should be a constant.
> This is going to vary from system to system. Can we put it in the
> device tree? I notice other devices have vref-supply in their
> bindings.
>
> I noticed that in_voltage_scale is writable. However, it did not
> accept any of the values I give it. Is this because we do not handle
> it in aspeed_adc_write_raw?
Yeah, that's an ugly quirk of IIO I wish we had done differently.
We don't have separate masks for read and write attributes, so there is
no way to have the attributes for the file set correctly.
>
> I suggest we add the reference in the device tree bindings, and also
> allow the value to be updated from userspace.
Not keen on updating from userspace, but indeed to providing it from
device tree. If there is a board out there where it is wrong the devicetree
should be fixed rather than applying a userspace hack. It's not as though
this device is likely to be accurate enough to warant a calibration procedure.
>
>> ---
>>
>> 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"
>
> You could just say Aspeed ADC to save us having to update it when the
> ast2600 comes out.
That's fine (and definitely a good thing if we end up supporting 20 different
variants in a few years time) but make sure to add it to the help text below
so there is something to grep for.
>
>> + 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.
>
> Don't forget to test compiling as a module.
>
>
>> 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
>
>> +#define ASPEED_ADC_NUM_CHANNELS 16
>> +#define ASPEED_ADC_REF_VOLTAGE 2500 /* millivolts */
>> +#define ASPEED_ADC_RESOLUTION_BITS 10
>> +#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)
>
> Nit: You could chose to label these with a shorter prefix. Drop the
> aspeed or adc, or both.
>
>> +
>> +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
>> + *val2 = 10;
>
> What does 10 mean?
>
>> + 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) {
>
> Handle IIO_CHAN_INFO_SCALE here too.
>
>> + 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,
>> + .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");
>
> The function you're calling will do that for you
>
> http://lxr.free-electrons.com/source/lib/devres.c?v=4.10#L134
>
> Just return the error here. I'd consider dropping the dev_errs for the
> other cases in the probe. We still get a reasonable error message
> without printing something ourselves. For example, when bailing out
> with ENOMEM:
>
> [ 5.510000] aspeed_adc: probe of 1e6e9000.adc failed with error -12
>
>
>> + ret = PTR_ERR(data->base);
>> + goto resource_error;
>> + }
>> +
>> + /* 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);
>
> I couldn't see any other drivers that use these functions outside of
> drivers/clk. I like what you've done here, but someone who understands
> the clock framework should take a look.
Agreed on both counts.
>
>
>> + if (IS_ERR(data->clk_prescaler)) {
>> + dev_err(&pdev->dev, "Failed allocating prescaler clock\n");
>> + ret = PTR_ERR(data->clk_prescaler);
>> + goto prescaler_error;
>> + }
>> +
>> + /*
>> + * 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);
>
> Should we be able to enable just the channels that we want? Perhaps
> only the ones that are requested through the device tree?
That is sometimes done for SoC ADCs as often people don't wire all
the channels out on a given board. Lots of examples in tree...
Leads to a slightly more fiddly driver, but not too bad.
>
>> +
>> + ret = iio_device_register(indio_dev);
>> + if (ret) {
>> + dev_err(&pdev->dev, "Could't register the device.\n");
>> + goto iio_register_error;
>> + }
>> +
>> + return 0;
>> +
>> +iio_register_error:
>> + writel(0x0, data->base + ASPEED_ADC_REG_ENGINE_CONTROL);
>
> Should this be done in remove as well?
>
>> + 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;
>
> You could just return from the error where it happens in the case
> where no cleanup is required.
>
>> +}
>> +
>> +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);
>> + 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" },
>> +};
>
> This is missing a null entry to terminate.
>
>> +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 at google.com>");
>> +MODULE_DESCRIPTION("Aspeed AST2400/2500 ADC Driver");
>> +MODULE_LICENSE("GPL");
>> --
>> 2.12.1.500.gab5fba24ee-goog
>>
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