[PATCH] aiodev: add driver for Rockchip SARADC

[Michael Riesch]

This commit adds support for the Successive Approximation Register (SAR)
ADCs that can be found in Rockchip SoCs, such as the RK3568.

Signed-off-by: Michael Riesch <michael.riesch at wolfvision.net>
---
 drivers/aiodev/Kconfig           |   7 ++
 drivers/aiodev/Makefile          |   1 +
 drivers/aiodev/rockchip_saradc.c | 153 +++++++++++++++++++++++++++++++
 3 files changed, 161 insertions(+)
 create mode 100644 drivers/aiodev/rockchip_saradc.c

diff --git a/drivers/aiodev/Kconfig b/drivers/aiodev/Kconfig
index 88d013aad..98223a8f9 100644
--- a/drivers/aiodev/Kconfig
+++ b/drivers/aiodev/Kconfig
@@ -50,4 +50,11 @@ config STM32_ADC
 	  Support for ADC on STM32.  Supports simple one-shot readings
 	  rather than continuous sampling with DMA, etc.  ADC channels should be
 	  configured via device tree, using the kernel bindings.
+
+config ROCKCHIP_SARADC
+	tristate "Rockchip SARADC driver"
+	depends on ARCH_RK3568
+	help
+	  Support for Successive Approximation Register (SAR) ADC in Rockchip
+	  SoCs.
 endif
diff --git a/drivers/aiodev/Makefile b/drivers/aiodev/Makefile
index 52652f67b..1b480f6fa 100644
--- a/drivers/aiodev/Makefile
+++ b/drivers/aiodev/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_MC13XXX_ADC) += mc13xxx_adc.o
 obj-$(CONFIG_QORIQ_THERMAL) += qoriq_thermal.o
 obj-$(CONFIG_AM335X_ADC) += am335x_adc.o
 obj-$(CONFIG_STM32_ADC) += stm32-adc.o stm32-adc-core.o
+obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
diff --git a/drivers/aiodev/rockchip_saradc.c b/drivers/aiodev/rockchip_saradc.c
new file mode 100644
index 000000000..abd7ccdd8
--- /dev/null
+++ b/drivers/aiodev/rockchip_saradc.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021, WolfVision GmbH
+ * Author: Michael Riesch <michael.riesch at wolfvision.net>
+ *
+ * Originally based on the Linux kernel v5.12 drivers/iio/adc/rockchip-saradc.c.
+ */
+
+#include <common.h>
+#include <aiodev.h>
+
+#define SARADC_DATA	       0x00
+
+#define SARADC_CTRL	       0x08
+#define SARADC_CTRL_IRQ_STATUS (1 << 6)
+#define SARADC_CTRL_IRQ_ENABLE (1 << 5)
+#define SARADC_CTRL_POWER_CTRL (1 << 3)
+#define SARADC_CTRL_CHN_MASK   0x07
+
+#define SARADC_DLY_PU_SOC      0x0c
+
+#define SARADC_TIMEOUT	       100
+
+struct rockchip_saradc_cfg {
+	unsigned int ref_voltage_mv;
+	unsigned int num_bits;
+	unsigned int num_channels;
+};
+
+struct rockchip_saradc_data {
+	const struct rockchip_saradc_cfg *config;
+	struct aiodevice aiodev;
+	void __iomem *base;
+	struct aiochannel *channels;
+};
+
+static inline void rockchip_saradc_reg_wr(struct rockchip_saradc_data *data,
+					  u32 value, u32 reg)
+{
+	writel(value, data->base + reg);
+}
+
+static inline u32 rockchip_saradc_reg_rd(struct rockchip_saradc_data *data,
+					 u32 reg)
+{
+	return readl(data->base + reg);
+}
+
+static int rockchip_saradc_read(struct aiochannel *chan, int *val)
+{
+	struct rockchip_saradc_data *data;
+	int timeout = SARADC_TIMEOUT;
+	u32 value = 0;
+	u32 control = 0;
+	u32 mask;
+
+	if (!chan || !val)
+		return -EINVAL;
+
+	data = container_of(chan->aiodev, struct rockchip_saradc_data, aiodev);
+	if (!data)
+		return -EINVAL;
+
+	rockchip_saradc_reg_wr(data, 8, SARADC_DLY_PU_SOC);
+	rockchip_saradc_reg_wr(data,
+			       (chan->index & SARADC_CTRL_CHN_MASK) |
+				       SARADC_CTRL_IRQ_ENABLE |
+				       SARADC_CTRL_POWER_CTRL,
+			       SARADC_CTRL);
+
+	do {
+		control = rockchip_saradc_reg_rd(data, SARADC_CTRL);
+
+		if (--timeout == 0)
+			return -ETIMEDOUT;
+		mdelay(1);
+	} while (!(control & SARADC_CTRL_IRQ_STATUS));
+
+	mask = (1 << data->config->num_bits) - 1;
+	value = rockchip_saradc_reg_rd(data, SARADC_DATA) & mask;
+	rockchip_saradc_reg_wr(data, 0, SARADC_CTRL);
+
+	printf("Raw value: %d\n", value);
+
+	*val = (value * data->config->ref_voltage_mv) / mask;
+
+	return 0;
+}
+
+static int rockchip_saradc_probe(struct device_d *dev)
+{
+	struct rockchip_saradc_data *data;
+	int i, ret;
+
+	data = xzalloc(sizeof(struct rockchip_saradc_data));
+	data->config = device_get_match_data(dev);
+	if (!data->config) {
+		ret = -EINVAL;
+		goto fail_data;
+	}
+	data->aiodev.hwdev = dev;
+	data->aiodev.read = rockchip_saradc_read;
+	data->base = dev_request_mem_region(dev, 0);
+	if (IS_ERR(data->base)) {
+		ret = PTR_ERR(data->base);
+		goto fail_data;
+	}
+
+	data->aiodev.num_channels = data->config->num_channels;
+	data->channels =
+		xzalloc(sizeof(*data->channels) * data->aiodev.num_channels);
+	data->aiodev.channels = xmalloc(sizeof(*data->aiodev.channels) *
+					data->aiodev.num_channels);
+	for (i = 0; i < data->aiodev.num_channels; i++) {
+		data->aiodev.channels[i] = &data->channels[i];
+		data->channels[i].unit = "mV";
+	}
+
+	rockchip_saradc_reg_wr(data, 0, SARADC_CTRL);
+
+	ret = aiodevice_register(&data->aiodev);
+	if (ret)
+		goto fail_channels;
+
+	dev_info(dev, "registered as %s\n", dev_name(&data->aiodev.dev));
+	return 0;
+
+fail_channels:
+	kfree(data->channels);
+	kfree(data->aiodev.channels);
+
+fail_data:
+	kfree(data);
+	return ret;
+}
+
+static const struct rockchip_saradc_cfg rk3568_saradc_cfg = {
+	.ref_voltage_mv = 1800,
+	.num_bits = 10,
+	.num_channels = 8,
+};
+
+static const struct of_device_id of_rockchip_saradc_match[] = {
+	{ .compatible = "rockchip,rk3568-saradc", .data = &rk3568_saradc_cfg },
+	{ /* end */ }
+};
+
+static struct driver_d rockchip_saradc_driver = {
+	.name = "rockchip_saradc",
+	.probe = rockchip_saradc_probe,
+	.of_compatible = DRV_OF_COMPAT(of_rockchip_saradc_match),
+};
+device_platform_driver(rockchip_saradc_driver);
-- 
2.20.1