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Subject[PATCH v3 1/3] mfd: upboard: Add UP2 platform controller driver
Date
UP Squared (UP2) is a x86 SBC from AAEON based on Intel Apollo Lake. It
features a MAX 10 FPGA that routes lines from both SoC and on-board
devices to two I/O headers:

+------------------------+
| 40-pin RPi-like header |
+------| (HAT) |
| +------------------------+
+-------+ +--------+
| | | | +------------------------+
| SoC |----| FPGA |-----| Custom UP2 pin header |
| | | | | (EXHAT) |
+-------+ +--------+ +------------------------+
|
+------* On-board devices: LED, VLS...

This is intended to enable vendor-specific applications to customize I/O
header pinout, as well as include low-latency functionality. It also
performs voltage level translation between the SoC (1.8V) and HAT header
(3.3V).

Out of the box, this block implements a platform controller with a
GPIO-bitbanged control interface. It's enumerated by ACPI and provides
registers to control:

- Configuration of all FPGA-routed header lines. These can be driven
SoC-to-header, header-to-SoC or set in high impedance.

- On-board LEDs and enable lines for other platform devices.

Add core support for this platform controller as a MFD device, exposing
these registers as a regmap.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dan O'Donovan <dan@emutex.com>
---
drivers/mfd/Kconfig | 17 +++
drivers/mfd/Makefile | 1 +
drivers/mfd/upboard.c | 336 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/mfd/upboard.h | 44 ++++++
4 files changed, 398 insertions(+)
create mode 100644 drivers/mfd/upboard.c
create mode 100644 include/linux/mfd/upboard.h

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 8c5dfdc..cccb901 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1871,6 +1871,23 @@ config MFD_STM32_TIMERS
for PWM and IIO Timer. This driver allow to share the
registers between the others drivers.

+config MFD_UPBOARD
+ tristate "UP Squared"
+ depends on ACPI
+ depends on GPIOLIB
+ select MFD_CORE
+ select REGMAP
+ help
+ If you say yes here you get support for the platform controller
+ of the UP Squared single-board computer.
+
+ This driver provides common support for accessing the device,
+ additional drivers must be enabled in order to use the
+ functionality of the device.
+
+ This driver can also be built as a module. If so, the module
+ will be called "upboard".
+
menu "Multimedia Capabilities Port drivers"
depends on ARCH_SA1100

diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 12980a4..593b86f 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -242,3 +242,4 @@ obj-$(CONFIG_MFD_SC27XX_PMIC) += sprd-sc27xx-spi.o
obj-$(CONFIG_RAVE_SP_CORE) += rave-sp.o
obj-$(CONFIG_MFD_ROHM_BD718XX) += rohm-bd718x7.o

+obj-$(CONFIG_MFD_UPBOARD) += upboard.o
diff --git a/drivers/mfd/upboard.c b/drivers/mfd/upboard.c
new file mode 100644
index 0000000..8b88731
--- /dev/null
+++ b/drivers/mfd/upboard.c
@@ -0,0 +1,336 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// UP Board platform controller driver
+//
+// Copyright (c) 2018, Emutex Ltd.
+//
+// Author: Javier Arteaga <javier@emutex.com>
+//
+
+#include <linux/acpi.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/upboard.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define UPBOARD_FW_BUILD_SHIFT 12
+#define UPBOARD_FW_MAJOR_SHIFT 8
+#define UPBOARD_FW_MINOR_SHIFT 4
+#define UPBOARD_FW_PATCH_SHIFT 0
+
+#define UPBOARD_FW_BUILD(id) (((id) >> UPBOARD_FW_BUILD_SHIFT) & 0x0f)
+#define UPBOARD_FW_MAJOR(id) (((id) >> UPBOARD_FW_MAJOR_SHIFT) & 0x0f)
+#define UPBOARD_FW_MINOR(id) (((id) >> UPBOARD_FW_MINOR_SHIFT) & 0x0f)
+#define UPBOARD_FW_PATCH(id) (((id) >> UPBOARD_FW_PATCH_SHIFT) & 0x0f)
+
+#define AAEON_MANUFACTURER_ID 0x01
+#define SUPPORTED_FW_MAJOR 0x0
+
+/* MSb of 8-bit address is an R/W flag */
+#define UPBOARD_ADDRESS_SIZE 8
+#define UPBOARD_READ_FLAG BIT(7)
+
+enum upboard_id {
+ UPBOARD_ID_UP2 = 1,
+};
+
+struct upboard_ddata {
+ struct gpio_desc *clear_gpio;
+ struct gpio_desc *strobe_gpio;
+ struct gpio_desc *datain_gpio;
+ struct gpio_desc *dataout_gpio;
+ const struct regmap_config *regmapconf;
+ const struct mfd_cell *cells;
+ size_t ncells;
+};
+
+/*
+ * UP boards include a platform controller with a proprietary GPIO-bitbanged
+ * control interface to access its configuration registers.
+ *
+ * The following macros and functions implement the read/write handlers for
+ * that interface, to provide a regmap-based abstraction for the controller.
+ */
+
+#define set_clear(u, x) gpiod_set_value((u)->clear_gpio, (x))
+#define set_strobe(u, x) gpiod_set_value((u)->strobe_gpio, (x))
+#define set_datain(u, x) gpiod_set_value((u)->datain_gpio, (x))
+#define get_dataout(u) gpiod_get_value((u)->dataout_gpio)
+
+static void __reg_io_start(const struct upboard_ddata * const ddata)
+{
+ /*
+ * CLEAR signal must be pulsed low before any register access.
+ * This resets internal counters in the controller and marks
+ * the start of a new register access.
+ */
+ set_clear(ddata, 0);
+ set_clear(ddata, 1);
+}
+
+static void __reg_io_end(const struct upboard_ddata * const ddata)
+{
+ /*
+ * STROBE signal must be cycled again to mark the end of a register
+ * access. Partial register accesses are discarded harmlessly
+ * by the controller if this final strobe cycle is not sent
+ */
+ set_strobe(ddata, 0);
+ set_strobe(ddata, 1);
+}
+
+static void __reg_io_write(const struct upboard_ddata * const ddata,
+ unsigned int size, unsigned int val)
+{
+ /*
+ * DATAIN is latched on each rising edge of the STROBE signal.
+ * Data (register address or value) is sent MSb first.
+ */
+ while (size--) {
+ set_strobe(ddata, 0);
+ set_datain(ddata, (val >> size) & 0x1);
+ set_strobe(ddata, 1);
+ }
+}
+
+static void __reg_io_read(const struct upboard_ddata * const ddata,
+ unsigned int size, unsigned int *val)
+{
+ /*
+ * DATAOUT is latched on on each rising edge of the STROBE signal.
+ * Data (register value) is received MSb first.
+ */
+ *val = 0;
+ while (size--) {
+ set_strobe(ddata, 0);
+ set_strobe(ddata, 1);
+ *val |= get_dataout(ddata) << size;
+ }
+}
+
+static int upboard_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+ const struct upboard_ddata * const ddata = context;
+
+ __reg_io_start(ddata);
+ __reg_io_write(ddata, UPBOARD_ADDRESS_SIZE, reg | UPBOARD_READ_FLAG);
+ __reg_io_read(ddata, UPBOARD_REGISTER_SIZE, val);
+ __reg_io_end(ddata);
+
+ return 0;
+}
+
+static int upboard_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+ const struct upboard_ddata * const ddata = context;
+
+ __reg_io_start(ddata);
+ __reg_io_write(ddata, UPBOARD_ADDRESS_SIZE, reg);
+ __reg_io_write(ddata, UPBOARD_REGISTER_SIZE, val);
+ __reg_io_end(ddata);
+
+ return 0;
+}
+
+/* UP Squared */
+
+static const struct regmap_range upboard_up2_readable_ranges[] = {
+ regmap_reg_range(UPBOARD_REG_PLATFORM_ID, UPBOARD_REG_FIRMWARE_ID),
+ regmap_reg_range(UPBOARD_REG_FUNC_EN0, UPBOARD_REG_FUNC_EN1),
+ regmap_reg_range(UPBOARD_REG_GPIO_EN0, UPBOARD_REG_GPIO_EN2),
+ regmap_reg_range(UPBOARD_REG_GPIO_DIR0, UPBOARD_REG_GPIO_DIR2),
+};
+
+static const struct regmap_range upboard_up2_writable_ranges[] = {
+ regmap_reg_range(UPBOARD_REG_FUNC_EN0, UPBOARD_REG_FUNC_EN1),
+ regmap_reg_range(UPBOARD_REG_GPIO_EN0, UPBOARD_REG_GPIO_EN2),
+ regmap_reg_range(UPBOARD_REG_GPIO_DIR0, UPBOARD_REG_GPIO_DIR2),
+};
+
+static const struct regmap_access_table upboard_up2_readable_table = {
+ .yes_ranges = upboard_up2_readable_ranges,
+ .n_yes_ranges = ARRAY_SIZE(upboard_up2_readable_ranges),
+};
+
+static const struct regmap_access_table upboard_up2_writable_table = {
+ .yes_ranges = upboard_up2_writable_ranges,
+ .n_yes_ranges = ARRAY_SIZE(upboard_up2_writable_ranges),
+};
+
+static const struct regmap_config upboard_up2_regmap_config = {
+ .reg_bits = UPBOARD_ADDRESS_SIZE,
+ .val_bits = UPBOARD_REGISTER_SIZE,
+ .max_register = UPBOARD_REG_MAX,
+ .reg_read = upboard_reg_read,
+ .reg_write = upboard_reg_write,
+ .fast_io = false,
+ .cache_type = REGCACHE_RBTREE,
+ .rd_table = &upboard_up2_readable_table,
+ .wr_table = &upboard_up2_writable_table,
+};
+
+static const struct mfd_cell upboard_up2_mfd_cells[] = {
+ {
+ .name = "upboard-led",
+ .id = 0,
+ },
+ {
+ .name = "upboard-led",
+ .id = 1,
+ },
+ {
+ .name = "upboard-led",
+ .id = 2,
+ },
+ {
+ .name = "upboard-led",
+ .id = 3,
+ },
+ {
+ .name = "upboard-pinctrl"
+ },
+};
+
+static int upboard_init_gpio(struct device *dev)
+{
+ struct upboard_ddata *ddata = dev_get_drvdata(dev);
+ struct gpio_desc *enable_gpio;
+
+ ddata->clear_gpio = devm_gpiod_get(dev, "clear", GPIOD_OUT_LOW);
+ if (IS_ERR(ddata->clear_gpio))
+ return PTR_ERR(ddata->clear_gpio);
+
+ ddata->strobe_gpio = devm_gpiod_get(dev, "strobe", GPIOD_OUT_LOW);
+ if (IS_ERR(ddata->strobe_gpio))
+ return PTR_ERR(ddata->strobe_gpio);
+
+ ddata->datain_gpio = devm_gpiod_get(dev, "datain", GPIOD_OUT_LOW);
+ if (IS_ERR(ddata->datain_gpio))
+ return PTR_ERR(ddata->datain_gpio);
+
+ ddata->dataout_gpio = devm_gpiod_get(dev, "dataout", GPIOD_IN);
+ if (IS_ERR(ddata->dataout_gpio))
+ return PTR_ERR(ddata->dataout_gpio);
+
+ /* External I/O signals are gated by ENABLE - ensure this is high */
+ enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
+ if (IS_ERR(enable_gpio))
+ return PTR_ERR(enable_gpio);
+
+ return 0;
+}
+
+static int upboard_check_supported(struct device *dev, struct regmap *regmap)
+{
+ uint8_t manufacturer_id, build, major, minor, patch;
+ unsigned int platform_id, firmware_id;
+ int ret;
+
+ ret = regmap_read(regmap, UPBOARD_REG_PLATFORM_ID, &platform_id);
+ if (ret)
+ return ret;
+
+ manufacturer_id = platform_id;
+ if (manufacturer_id != AAEON_MANUFACTURER_ID) {
+ dev_err(dev,
+ "unsupported FPGA firmware from manufacturer 0x%02x",
+ manufacturer_id);
+ return -ENODEV;
+ }
+
+ ret = regmap_read(regmap, UPBOARD_REG_FIRMWARE_ID, &firmware_id);
+ if (ret)
+ return ret;
+
+ build = UPBOARD_FW_BUILD(firmware_id);
+ major = UPBOARD_FW_MAJOR(firmware_id);
+ minor = UPBOARD_FW_MINOR(firmware_id);
+ patch = UPBOARD_FW_PATCH(firmware_id);
+ if (major != SUPPORTED_FW_MAJOR) {
+ dev_err(dev, "unsupported FPGA firmware v%u.%u.%u.%u",
+ major, minor, patch, build);
+ return -ENODEV;
+ }
+
+ dev_dbg(dev, "supported FPGA firmware v%u.%u.%u.%u",
+ major, minor, patch, build);
+ return 0;
+}
+
+static const struct acpi_device_id upboard_acpi_match[] = {
+ { "AANT0F01", (kernel_ulong_t)UPBOARD_ID_UP2 },
+ { }
+};
+MODULE_DEVICE_TABLE(acpi, upboard_acpi_match);
+
+static int upboard_match_device(struct device *dev)
+{
+ struct upboard_ddata *ddata = dev_get_drvdata(dev);
+ enum upboard_id id = (kernel_ulong_t)device_get_match_data(dev);
+
+ switch (id) {
+ case UPBOARD_ID_UP2:
+ ddata->regmapconf = &upboard_up2_regmap_config;
+ ddata->cells = upboard_up2_mfd_cells;
+ ddata->ncells = ARRAY_SIZE(upboard_up2_mfd_cells);
+ break;
+ default:
+ dev_err(dev, "unsupported ID %u\n", id);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int upboard_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct upboard_ddata *ddata;
+ struct regmap *regmap;
+ int ret;
+
+ ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+ if (!ddata)
+ return -ENOMEM;
+
+ dev_set_drvdata(dev, ddata);
+
+ ret = upboard_match_device(dev);
+ if (ret)
+ return ret;
+
+ regmap = devm_regmap_init(dev, NULL, ddata, ddata->regmapconf);
+ if (IS_ERR(regmap))
+ return PTR_ERR(regmap);
+
+ ret = upboard_init_gpio(dev);
+ if (ret) {
+ if (ret != -EPROBE_DEFER)
+ dev_err(dev, "failed to init GPIOs: %d", ret);
+ return ret;
+ }
+
+ ret = upboard_check_supported(dev, regmap);
+ if (ret)
+ return ret;
+
+ return devm_mfd_add_devices(dev, 0, ddata->cells, ddata->ncells,
+ NULL, 0, NULL);
+}
+
+static struct platform_driver upboard_driver = {
+ .probe = upboard_probe,
+ .driver = {
+ .name = "upboard",
+ .acpi_match_table = upboard_acpi_match,
+ },
+};
+
+module_platform_driver(upboard_driver);
+
+MODULE_AUTHOR("Javier Arteaga <javier@emutex.com>");
+MODULE_DESCRIPTION("UP Board platform controller driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/upboard.h b/include/linux/mfd/upboard.h
new file mode 100644
index 0000000..63e677f
--- /dev/null
+++ b/include/linux/mfd/upboard.h
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// UP Board MFD driver interface
+//
+// Copyright (c) 2018, Emutex Ltd.
+//
+// Author: Javier Arteaga <javier@emutex.com>
+//
+
+#ifndef __LINUX_MFD_UPBOARD_H
+#define __LINUX_MFD_UPBOARD_H
+
+#define UPBOARD_REGISTER_SIZE 16
+
+/**
+ * enum upboard_reg - addresses for 16-bit controller registers
+ *
+ * @UPBOARD_REG_PLATFORM_ID: [RO] BOARD_ID | MANUFACTURER_ID
+ * @UPBOARD_REG_FIRMWARE_ID: [RO] BUILD | MAJOR | MINOR | PATCH
+ * @UPBOARD_REG_FUNC_EN0: [RW] Toggles for board functions (bank 0)
+ * @UPBOARD_REG_FUNC_EN1: [RW] Toggles for board functions (bank 1)
+ * @UPBOARD_REG_GPIO_EN0: [RW] Hi-Z (0) / enabled (1) GPIO (bank 0)
+ * @UPBOARD_REG_GPIO_EN1: [RW] Hi-Z (0) / enabled (1) GPIO (bank 1)
+ * @UPBOARD_REG_GPIO_EN2: [RW] Hi-Z (0) / enabled (1) GPIO (bank 2)
+ * @UPBOARD_REG_GPIO_DIR0: [RW] SoC- (0) / FPGA- (1) driven GPIO (bank 0)
+ * @UPBOARD_REG_GPIO_DIR1: [RW] SoC- (0) / FPGA- (1) driven GPIO (bank 1)
+ * @UPBOARD_REG_GPIO_DIR2: [RW] SoC- (0) / FPGA- (1) driven GPIO (bank 2)
+ * @UPBOARD_REG_MAX: one past the last valid address
+ */
+enum upboard_reg {
+ UPBOARD_REG_PLATFORM_ID = 0x10,
+ UPBOARD_REG_FIRMWARE_ID = 0x11,
+ UPBOARD_REG_FUNC_EN0 = 0x20,
+ UPBOARD_REG_FUNC_EN1 = 0x21,
+ UPBOARD_REG_GPIO_EN0 = 0x30,
+ UPBOARD_REG_GPIO_EN1 = 0x31,
+ UPBOARD_REG_GPIO_EN2 = 0x32,
+ UPBOARD_REG_GPIO_DIR0 = 0x40,
+ UPBOARD_REG_GPIO_DIR1 = 0x41,
+ UPBOARD_REG_GPIO_DIR2 = 0x42,
+ UPBOARD_REG_MAX,
+};
+
+#endif /* __LINUX_MFD_UPBOARD_H */
--
2.7.4

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