| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Driver for ADC module on the Cirrus Logic EP93xx series of SoCs |
| * |
| * Copyright (C) 2015 Alexander Sverdlin |
| * |
| * The driver uses polling to get the conversion status. According to EP93xx |
| * datasheets, reading ADCResult register starts the conversion, but user is also |
| * responsible for ensuring that delay between adjacent conversion triggers is |
| * long enough so that maximum allowed conversion rate is not exceeded. This |
| * basically renders IRQ mode unusable. |
| */ |
| |
| #include <linux/clk.h> |
| #include <linux/delay.h> |
| #include <linux/device.h> |
| #include <linux/err.h> |
| #include <linux/iio/iio.h> |
| #include <linux/io.h> |
| #include <linux/irqflags.h> |
| #include <linux/module.h> |
| #include <linux/mutex.h> |
| #include <linux/platform_device.h> |
| |
| /* |
| * This code could benefit from real HR Timers, but jiffy granularity would |
| * lower ADC conversion rate down to CONFIG_HZ, so we fallback to busy wait |
| * in such case. |
| * |
| * HR Timers-based version loads CPU only up to 10% during back to back ADC |
| * conversion, while busy wait-based version consumes whole CPU power. |
| */ |
| #ifdef CONFIG_HIGH_RES_TIMERS |
| #define ep93xx_adc_delay(usmin, usmax) usleep_range(usmin, usmax) |
| #else |
| #define ep93xx_adc_delay(usmin, usmax) udelay(usmin) |
| #endif |
| |
| #define EP93XX_ADC_RESULT 0x08 |
| #define EP93XX_ADC_SDR BIT(31) |
| #define EP93XX_ADC_SWITCH 0x18 |
| #define EP93XX_ADC_SW_LOCK 0x20 |
| |
| struct ep93xx_adc_priv { |
| struct clk *clk; |
| void __iomem *base; |
| int lastch; |
| struct mutex lock; |
| }; |
| |
| #define EP93XX_ADC_CH(index, dname, swcfg) { \ |
| .type = IIO_VOLTAGE, \ |
| .indexed = 1, \ |
| .channel = index, \ |
| .address = swcfg, \ |
| .datasheet_name = dname, \ |
| .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ |
| .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) | \ |
| BIT(IIO_CHAN_INFO_OFFSET), \ |
| } |
| |
| /* |
| * Numbering scheme for channels 0..4 is defined in EP9301 and EP9302 datasheets. |
| * EP9307, EP9312 and EP9312 have 3 channels more (total 8), but the numbering is |
| * not defined. So the last three are numbered randomly, let's say. |
| */ |
| static const struct iio_chan_spec ep93xx_adc_channels[8] = { |
| EP93XX_ADC_CH(0, "YM", 0x608), |
| EP93XX_ADC_CH(1, "SXP", 0x680), |
| EP93XX_ADC_CH(2, "SXM", 0x640), |
| EP93XX_ADC_CH(3, "SYP", 0x620), |
| EP93XX_ADC_CH(4, "SYM", 0x610), |
| EP93XX_ADC_CH(5, "XP", 0x601), |
| EP93XX_ADC_CH(6, "XM", 0x602), |
| EP93XX_ADC_CH(7, "YP", 0x604), |
| }; |
| |
| static int ep93xx_read_raw(struct iio_dev *iiodev, |
| struct iio_chan_spec const *channel, int *value, |
| int *shift, long mask) |
| { |
| struct ep93xx_adc_priv *priv = iio_priv(iiodev); |
| unsigned long timeout; |
| int ret; |
| |
| switch (mask) { |
| case IIO_CHAN_INFO_RAW: |
| mutex_lock(&priv->lock); |
| if (priv->lastch != channel->channel) { |
| priv->lastch = channel->channel; |
| /* |
| * Switch register is software-locked, unlocking must be |
| * immediately followed by write |
| */ |
| local_irq_disable(); |
| writel_relaxed(0xAA, priv->base + EP93XX_ADC_SW_LOCK); |
| writel_relaxed(channel->address, |
| priv->base + EP93XX_ADC_SWITCH); |
| local_irq_enable(); |
| /* |
| * Settling delay depends on module clock and could be |
| * 2ms or 500us |
| */ |
| ep93xx_adc_delay(2000, 2000); |
| } |
| /* Start the conversion, eventually discarding old result */ |
| readl_relaxed(priv->base + EP93XX_ADC_RESULT); |
| /* Ensure maximum conversion rate is not exceeded */ |
| ep93xx_adc_delay(DIV_ROUND_UP(1000000, 925), |
| DIV_ROUND_UP(1000000, 925)); |
| /* At this point conversion must be completed, but anyway... */ |
| ret = IIO_VAL_INT; |
| timeout = jiffies + msecs_to_jiffies(1) + 1; |
| while (1) { |
| u32 t; |
| |
| t = readl_relaxed(priv->base + EP93XX_ADC_RESULT); |
| if (t & EP93XX_ADC_SDR) { |
| *value = sign_extend32(t, 15); |
| break; |
| } |
| |
| if (time_after(jiffies, timeout)) { |
| dev_err(&iiodev->dev, "Conversion timeout\n"); |
| ret = -ETIMEDOUT; |
| break; |
| } |
| |
| cpu_relax(); |
| } |
| mutex_unlock(&priv->lock); |
| return ret; |
| |
| case IIO_CHAN_INFO_OFFSET: |
| /* According to datasheet, range is -25000..25000 */ |
| *value = 25000; |
| return IIO_VAL_INT; |
| |
| case IIO_CHAN_INFO_SCALE: |
| /* Typical supply voltage is 3.3v */ |
| *value = (1ULL << 32) * 3300 / 50000; |
| *shift = 32; |
| return IIO_VAL_FRACTIONAL_LOG2; |
| } |
| |
| return -EINVAL; |
| } |
| |
| static const struct iio_info ep93xx_adc_info = { |
| .read_raw = ep93xx_read_raw, |
| }; |
| |
| static int ep93xx_adc_probe(struct platform_device *pdev) |
| { |
| int ret; |
| struct iio_dev *iiodev; |
| struct ep93xx_adc_priv *priv; |
| struct clk *pclk; |
| struct resource *res; |
| |
| iiodev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv)); |
| if (!iiodev) |
| return -ENOMEM; |
| priv = iio_priv(iiodev); |
| |
| res = platform_get_resource(pdev, IORESOURCE_MEM, 0); |
| priv->base = devm_ioremap_resource(&pdev->dev, res); |
| if (IS_ERR(priv->base)) { |
| dev_err(&pdev->dev, "Cannot map memory resource\n"); |
| return PTR_ERR(priv->base); |
| } |
| |
| iiodev->dev.parent = &pdev->dev; |
| iiodev->name = dev_name(&pdev->dev); |
| iiodev->modes = INDIO_DIRECT_MODE; |
| iiodev->info = &ep93xx_adc_info; |
| iiodev->num_channels = ARRAY_SIZE(ep93xx_adc_channels); |
| iiodev->channels = ep93xx_adc_channels; |
| |
| priv->lastch = -1; |
| mutex_init(&priv->lock); |
| |
| platform_set_drvdata(pdev, iiodev); |
| |
| priv->clk = devm_clk_get(&pdev->dev, NULL); |
| if (IS_ERR(priv->clk)) { |
| dev_err(&pdev->dev, "Cannot obtain clock\n"); |
| return PTR_ERR(priv->clk); |
| } |
| |
| pclk = clk_get_parent(priv->clk); |
| if (!pclk) { |
| dev_warn(&pdev->dev, "Cannot obtain parent clock\n"); |
| } else { |
| /* |
| * This is actually a place for improvement: |
| * EP93xx ADC supports two clock divisors -- 4 and 16, |
| * resulting in conversion rates 3750 and 925 samples per second |
| * with 500us or 2ms settling time respectively. |
| * One might find this interesting enough to be configurable. |
| */ |
| ret = clk_set_rate(priv->clk, clk_get_rate(pclk) / 16); |
| if (ret) |
| dev_warn(&pdev->dev, "Cannot set clock rate\n"); |
| /* |
| * We can tolerate rate setting failure because the module should |
| * work in any case. |
| */ |
| } |
| |
| ret = clk_enable(priv->clk); |
| if (ret) { |
| dev_err(&pdev->dev, "Cannot enable clock\n"); |
| return ret; |
| } |
| |
| ret = iio_device_register(iiodev); |
| if (ret) |
| clk_disable(priv->clk); |
| |
| return ret; |
| } |
| |
| static int ep93xx_adc_remove(struct platform_device *pdev) |
| { |
| struct iio_dev *iiodev = platform_get_drvdata(pdev); |
| struct ep93xx_adc_priv *priv = iio_priv(iiodev); |
| |
| iio_device_unregister(iiodev); |
| clk_disable(priv->clk); |
| |
| return 0; |
| } |
| |
| static struct platform_driver ep93xx_adc_driver = { |
| .driver = { |
| .name = "ep93xx-adc", |
| }, |
| .probe = ep93xx_adc_probe, |
| .remove = ep93xx_adc_remove, |
| }; |
| module_platform_driver(ep93xx_adc_driver); |
| |
| MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@gmail.com>"); |
| MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver"); |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS("platform:ep93xx-adc"); |