[PATCH v3 2/2] i2c: keba: Add KEBA I2C controller support

Gerhard Engleder
2024-07-10T17:57:17Z

From: Gerhard Engleder <eg@keba.com>

The KEBA I2C controller is found in the system FPGA of KEBA PLC devices.
It is used to connect EEPROMs and hardware monitoring chips. The

It is a simple I2C controller with a fixed bus speed of 100 kbit/s. The
whole message transmission is executed by the driver. The driver
triggers all steps over control, status and data register. There are no
FIFOs or interrupts.

Signed-off-by: Gerhard Engleder <eg@keba.com>
---
drivers/i2c/busses/Kconfig | 11 +
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-keba.c | 593 ++++++++++++++++++++++++++++++++++
3 files changed, 605 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-keba.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 3e32fb882101..41162130c6f2 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -771,6 +771,17 @@ config I2C_JZ4780

If you don't know what to do here, say N.

+config I2C_KEBA
+ tristate "KEBA I2C controller support"
+ depends on HAS_IOMEM
+ select AUXILIARY_BUS
+ help
+ This driver supports the I2C controller found in KEBA system FPGA
+ devices.
+
+ This driver can also be built as a module. If so, the module
+ will be called i2c-keba.
+
config I2C_KEMPLD
tristate "Kontron COM I2C Controller"
depends on MFD_KEMPLD
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 78d0561339e5..ecc07c50f2a0 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_I2C_IMX) += i2c-imx.o
obj-$(CONFIG_I2C_IMX_LPI2C) += i2c-imx-lpi2c.o
obj-$(CONFIG_I2C_IOP3XX) += i2c-iop3xx.o
obj-$(CONFIG_I2C_JZ4780) += i2c-jz4780.o
+obj-$(CONFIG_I2C_KEBA) += i2c-keba.o
obj-$(CONFIG_I2C_KEMPLD) += i2c-kempld.o
obj-$(CONFIG_I2C_LPC2K) += i2c-lpc2k.o
obj-$(CONFIG_I2C_LS2X) += i2c-ls2x.o
diff --git a/drivers/i2c/busses/i2c-keba.c b/drivers/i2c/busses/i2c-keba.c
new file mode 100644
index 000000000000..400015e4ac77
--- /dev/null
+++ b/drivers/i2c/busses/i2c-keba.c
@@ -0,0 +1,593 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) KEBA Industrial Automation Gmbh 2024
+ *
+ * Driver for KEBA I2C controller FPGA IP core
+ */
+
+#include <linux/i2c.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/misc/keba.h>
+
+#define KI2C "i2c-keba"
+
+#define KI2C_CAPABILITY_REG 0x02
+#define KI2C_CAPABILITY_CRYPTO 0x01
+#define KI2C_CAPABILITY_DC 0x02
+
+#define KI2C_CONTROL_REG 0x04
+#define KI2C_CONTROL_MEN 0x01
+#define KI2C_CONTROL_MSTA 0x02
+#define KI2C_CONTROL_RSTA 0x04
+#define KI2C_CONTROL_MTX 0x08
+#define KI2C_CONTROL_TXAK 0x10
+#define KI2C_CONTROL_DISABLE 0x00
+
+#define KI2C_CONTROL_DC_REG 0x05
+#define KI2C_CONTROL_DC_SDA 0x01
+#define KI2C_CONTROL_DC_SCL 0x02
+
+#define KI2C_STATUS_REG 0x08
+#define KI2C_STATUS_IN_USE 0x01
+#define KI2C_STATUS_ACK_CYC 0x02
+#define KI2C_STATUS_RXAK 0x04
+#define KI2C_STATUS_MCF 0x08
+
+#define KI2C_STATUS_DC_REG 0x09
+#define KI2C_STATUS_DC_SDA 0x01
+#define KI2C_STATUS_DC_SCL 0x02
+
+#define KI2C_DATA_REG 0x0c
+
+#define KI2C_INUSE_SLEEP_US (2 * USEC_PER_MSEC)
+#define KI2C_INUSE_TIMEOUT_US (10 * USEC_PER_SEC)
+
+#define KI2C_POLL_DELAY_US 5
+
+struct ki2c {
+ struct keba_i2c_auxdev *auxdev;
+ void __iomem *base;
+ struct i2c_adapter adapter;
+
+ struct i2c_client **client;
+ int client_size;
+};
+
+static int ki2c_inuse_lock(struct ki2c *ki2c)
+{
+ u8 sts;
+ int ret;
+
+ /*
+ * The I2C controller has an IN_USE bit for locking access to the
+ * controller. This enables the use of I2C controller by other none
+ * Linux processors.
+ *
+ * If the I2C controller is free, then the first read returns
+ * IN_USE == 0. After that the I2C controller is locked and further
+ * reads of IN_USE return 1.
+ *
+ * The I2C controller is unlocked by writing 1 into IN_USE.
+ *
+ * The IN_USE bit acts as a hardware semaphore for the I2C controller.
+ * Poll for semaphore, but sleep while polling to free the CPU.
+ */
+ ret = readb_poll_timeout(ki2c->base + KI2C_STATUS_REG,
+ sts, (sts & KI2C_STATUS_IN_USE) == 0,
+ KI2C_INUSE_SLEEP_US, KI2C_INUSE_TIMEOUT_US);
+ if (ret != 0)
+ dev_warn(&ki2c->auxdev->auxdev.dev, "%s err!\n", __func__);
+
+ return ret;
+}
+
+static void ki2c_inuse_unlock(struct ki2c *ki2c)
+{
+ /* unlock the controller by writing 1 into IN_USE */
+ iowrite8(KI2C_STATUS_IN_USE, ki2c->base + KI2C_STATUS_REG);
+}
+
+static int ki2c_wait_for_bit(void __iomem *addr, u8 mask, unsigned long timeout)
+{
+ u8 val;
+
+ return readb_poll_timeout(addr, val, (val & mask), KI2C_POLL_DELAY_US,
+ jiffies_to_usecs(timeout));
+}
+
+static int ki2c_wait_for_mcf(struct ki2c *ki2c)
+{
+ return ki2c_wait_for_bit(ki2c->base + KI2C_STATUS_REG, KI2C_STATUS_MCF,
+ ki2c->adapter.timeout);
+}
+
+static int ki2c_wait_for_data(struct ki2c *ki2c)
+{
+ int ret;
+
+ ret = ki2c_wait_for_mcf(ki2c);
+ if (ret < 0)
+ return ret;
+
+ return ki2c_wait_for_bit(ki2c->base + KI2C_STATUS_REG,
+ KI2C_STATUS_ACK_CYC,
+ ki2c->adapter.timeout);
+}
+
+static int ki2c_wait_for_data_ack(struct ki2c *ki2c)
+{
+ unsigned int reg;
+ int ret;
+
+ ret = ki2c_wait_for_data(ki2c);
+ if (ret < 0)
+ return ret;
+
+ /* RXAK == 0 means ACK reveived */
+ reg = ioread8(ki2c->base + KI2C_STATUS_REG);
+ if (reg & KI2C_STATUS_RXAK)
+ return -EIO;
+
+ return 0;
+}
+
+static int ki2c_has_capability(struct ki2c *ki2c, unsigned int cap)
+{
+ unsigned int reg = ioread8(ki2c->base + KI2C_CAPABILITY_REG);
+
+ return (reg & cap) != 0;
+}
+
+static int ki2c_get_scl(struct ki2c *ki2c)
+{
+ unsigned int reg = ioread8(ki2c->base + KI2C_STATUS_DC_REG);
+
+ /* capability KI2C_CAPABILITY_DC required */
+ return (reg & KI2C_STATUS_DC_SCL) != 0;
+}
+
+static int ki2c_get_sda(struct ki2c *ki2c)
+{
+ unsigned int reg = ioread8(ki2c->base + KI2C_STATUS_DC_REG);
+
+ /* capability KI2C_CAPABILITY_DC required */
+ return (reg & KI2C_STATUS_DC_SDA) != 0;
+}
+
+static void ki2c_set_scl(struct ki2c *ki2c, int val)
+{
+ u8 control_dc;
+
+ /* capability KI2C_CAPABILITY_DC and KI2C_CONTROL_MEN = 0 reqired */
+ control_dc = ioread8(ki2c->base + KI2C_CONTROL_DC_REG);
+ if (val)
+ control_dc |= KI2C_CONTROL_DC_SCL;
+ else
+ control_dc &= ~KI2C_CONTROL_DC_SCL;
+ iowrite8(control_dc, ki2c->base + KI2C_CONTROL_DC_REG);
+}
+
+/*
+ * Resetting bus bitwise is done by checking SDA and applying clock cycles as
+ * long as SDA is low. 9 clock cycles are applied at most.
+ *
+ * Clock cycles are generated and ndelay() determines the duration of clock
+ * cycles. Generated clock rate is 100 KHz and so duration of both clock levels
+ * is: delay in ns = (10^6 / 100) / 2
+ */
+#define KI2C_RECOVERY_CLK_CNT 9
+#define KI2C_RECOVERY_NDELAY 5000
+static int ki2c_reset_bus_bitwise(struct ki2c *ki2c)
+{
+ int count = 0;
+ int val = 1;
+ int ret = 0;
+
+ /* disable I2C controller (MEN = 0) to get direct access to SCL/SDA */
+ iowrite8(0, ki2c->base + KI2C_CONTROL_REG);
+
+ /* generate clock cycles */
+ ki2c_set_scl(ki2c, val);
+ ndelay(KI2C_RECOVERY_NDELAY);
+ while (count++ < KI2C_RECOVERY_CLK_CNT * 2) {
+ if (val) {
+ /* SCL shouldn't be low here */
+ if (!ki2c_get_scl(ki2c)) {
+ dev_err(&ki2c->auxdev->auxdev.dev,
+ "SCL is stuck low!\n");
+ ret = -EBUSY;
+ break;
+ }
+
+ /* break if SDA is high */
+ if (ki2c_get_sda(ki2c))
+ break;
+ }
+
+ val = !val;
+ ki2c_set_scl(ki2c, val);
+ ndelay(KI2C_RECOVERY_NDELAY);
+ }
+
+ if (!ki2c_get_sda(ki2c)) {
+ dev_err(&ki2c->auxdev->auxdev.dev, "SDA is still low!\n");
+ ret = -EBUSY;
+ }
+
+ /* reenable controller */
+ iowrite8(KI2C_CONTROL_MEN, ki2c->base + KI2C_CONTROL_REG);
+
+ return ret;
+}
+
+/*
+ * Resetting bus bytewise is done by writing start bit, 9 data bits and stop
+ * bit.
+ *
+ * This is not 100% safe. If slave is an EEPROM and a write access was
+ * interrupted during the ACK cycle, this approach might not be able to recover
+ * the bus. The reason is, that after the 9 clock cycles the EEPROM will be in
+ * ACK cycle again and will hold SDA low like it did before the start of the
+ * routine. Furthermore the EEPROM might get written one additional byte with
+ * 0xff into it. Thus, use bitwise approach whenever possible, especially when
+ * EEPROMs are on the bus.
+ */
+static int ki2c_reset_bus_bytewise(struct ki2c *ki2c)
+{
+ int ret;
+
+ /* hold data line high for 9 clock cycles */
+ iowrite8(0xFF, ki2c->base + KI2C_DATA_REG);
+
+ /* create start condition */
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MTX | KI2C_CONTROL_MSTA | KI2C_CONTROL_TXAK,
+ ki2c->base + KI2C_CONTROL_REG);
+ ret = ki2c_wait_for_mcf(ki2c);
+ if (ret < 0) {
+ dev_err(&ki2c->auxdev->auxdev.dev, "Start condition failed\n");
+
+ return ret;
+ }
+
+ /* create stop condition */
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MTX | KI2C_CONTROL_TXAK,
+ ki2c->base + KI2C_CONTROL_REG);
+ ret = ki2c_wait_for_mcf(ki2c);
+ if (ret < 0)
+ dev_err(&ki2c->auxdev->auxdev.dev, "Stop condition failed\n");
+
+ return ret;
+}
+
+static int ki2c_reset_bus(struct ki2c *ki2c)
+{
+ int ret;
+
+ ret = ki2c_inuse_lock(ki2c);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * If the I2C controller is capable of direct control of SCL/SDA, then a
+ * bitwise reset is used. Otherwise fall back to bytewise reset.
+ */
+ if (ki2c_has_capability(ki2c, KI2C_CAPABILITY_DC))
+ ret = ki2c_reset_bus_bitwise(ki2c);
+ else
+ ret = ki2c_reset_bus_bytewise(ki2c);
+
+ ki2c_inuse_unlock(ki2c);
+
+ return ret;
+}
+
+static void ki2c_write_target_addr(struct ki2c *ki2c, struct i2c_msg *m)
+{
+ u8 addr;
+
+ addr = m->addr << 1;
+ /* Bit 0 signals RD/WR */
+ if (m->flags & I2C_M_RD)
+ addr |= 0x01;
+
+ iowrite8(addr, ki2c->base + KI2C_DATA_REG);
+}
+
+static int ki2c_start_addr(struct ki2c *ki2c, struct i2c_msg *m)
+{
+ int ret;
+
+ /*
+ * Store target address byte in the controller. This has to be done
+ * before sending START condition.
+ */
+ ki2c_write_target_addr(ki2c, m);
+
+ /* enable controller for TX */
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MTX,
+ ki2c->base + KI2C_CONTROL_REG);
+
+ /* send START condition and target address byte */
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MTX | KI2C_CONTROL_MSTA,
+ ki2c->base + KI2C_CONTROL_REG);
+
+ ret = ki2c_wait_for_data_ack(ki2c);
+ if (ret < 0)
+ /*
+ * For EEPROMs this is normal behavior during internal write
+ * operation.
+ */
+ dev_dbg(&ki2c->auxdev->auxdev.dev,
+ "%s wait for ACK err at 0x%02x!\n", __func__, m->addr);
+
+ return ret;
+}
+
+static int ki2c_repstart_addr(struct ki2c *ki2c, struct i2c_msg *m)
+{
+ int ret;
+
+ /* repeated start and write is not supported */
+ if ((m->flags & I2C_M_RD) == 0) {
+ dev_warn(&ki2c->auxdev->auxdev.dev,
+ "Repeated start not supported for writes\n");
+ return -EINVAL;
+ }
+
+ /* send repeated start */
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MSTA | KI2C_CONTROL_RSTA,
+ ki2c->base + KI2C_CONTROL_REG);
+
+ ret = ki2c_wait_for_mcf(ki2c);
+ if (ret < 0) {
+ dev_warn(&ki2c->auxdev->auxdev.dev,
+ "%s wait for MCF err at 0x%02x!\n", __func__, m->addr);
+ return ret;
+ }
+
+ /* write target-address byte */
+ ki2c_write_target_addr(ki2c, m);
+
+ ret = ki2c_wait_for_data_ack(ki2c);
+ if (ret < 0)
+ dev_warn(&ki2c->auxdev->auxdev.dev,
+ "%s wait for ACK err at 0x%02x!\n", __func__, m->addr);
+
+ return ret;
+}
+
+static void ki2c_stop(struct ki2c *ki2c)
+{
+ iowrite8(KI2C_CONTROL_MEN, ki2c->base + KI2C_CONTROL_REG);
+ ki2c_wait_for_mcf(ki2c);
+}
+
+static int ki2c_write(struct ki2c *ki2c, const u8 *data, int len)
+{
+ int ret;
+
+ for (int i = 0; i < len; i++) {
+ /* write data byte */
+ iowrite8(data[i], ki2c->base + KI2C_DATA_REG);
+
+ ret = ki2c_wait_for_data_ack(ki2c);
+ if (ret < 0)
+ return ret;
+ }
+
+ return 0;
+}
+
+static int ki2c_read(struct ki2c *ki2c, u8 *data, int len)
+{
+ u8 control;
+ int ret;
+
+ if (len == 0)
+ return 0; /* nothing to do */
+
+ control = KI2C_CONTROL_MEN | KI2C_CONTROL_MSTA;
+
+ /* if just one byte => send tx-nack after transfer */
+ if (len == 1)
+ control |= KI2C_CONTROL_TXAK;
+
+ iowrite8(control, ki2c->base + KI2C_CONTROL_REG);
+
+ /* dummy read to start transfer on bus */
+ ioread8(ki2c->base + KI2C_DATA_REG);
+
+ for (int i = 0; i < len; i++) {
+ ret = ki2c_wait_for_data(ki2c);
+ if (ret < 0)
+ return ret;
+
+ /* send tx-nack after transfer of last byte */
+ if (i == len - 2)
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MSTA | KI2C_CONTROL_TXAK,
+ ki2c->base + KI2C_CONTROL_REG);
+
+ /*
+ * switch to TX on last byte, so that reading DATA-register
+ * does not trigger another read transfer.
+ */
+ if (i == len - 1)
+ iowrite8(KI2C_CONTROL_MEN | KI2C_CONTROL_MSTA | KI2C_CONTROL_MTX,
+ ki2c->base + KI2C_CONTROL_REG);
+
+ /* read byte and start next transfer (if not last byte) */
+ data[i] = ioread8(ki2c->base + KI2C_DATA_REG);
+ }
+
+ return len;
+}
+
+static int ki2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
+{
+ struct ki2c *ki2c = i2c_get_adapdata(adap);
+ int ret;
+
+ ret = ki2c_inuse_lock(ki2c);
+ if (ret < 0)
+ return ret;
+
+ for (int i = 0; i < num; i++) {
+ struct i2c_msg *m = &msgs[i];
+
+ if (i == 0)
+ ret = ki2c_start_addr(ki2c, m);
+ else
+ ret = ki2c_repstart_addr(ki2c, m);
+ if (ret < 0)
+ break;
+
+ if (m->flags & I2C_M_RD)
+ ret = ki2c_read(ki2c, m->buf, m->len);
+ else
+ ret = ki2c_write(ki2c, m->buf, m->len);
+ if (ret < 0)
+ break;
+ }
+
+ ki2c_stop(ki2c);
+
+ ki2c_inuse_unlock(ki2c);
+
+ return (ret < 0) ? ret : num;
+}
+
+static void ki2c_unregister_devices(struct ki2c *ki2c)
+{
+ for (int i = 0; i < ki2c->client_size; i++) {
+ struct i2c_client *client = ki2c->client[i];
+
+ if (client)
+ i2c_unregister_device(client);
+ }
+}
+
+static int ki2c_register_devices(struct ki2c *ki2c)
+{
+ struct i2c_board_info *info = ki2c->auxdev->info;
+ int i;
+
+ /* register all I2C devices from platform_data array */
+ for (i = 0; i < ki2c->client_size; i++) {
+ struct i2c_client *client;
+ unsigned short const addr_list[2] = { info[i].addr,
+ I2C_CLIENT_END };
+
+ client = i2c_new_scanned_device(&ki2c->adapter, &info[i],
+ addr_list, NULL);
+ if (!IS_ERR(client)) {
+ ki2c->client[i] = client;
+ } else if (PTR_ERR(client) != -ENODEV) {
+ ki2c_unregister_devices(ki2c);
+
+ return PTR_ERR(client);
+ }
+ }
+
+ return 0;
+}
+
+static u32 ki2c_func(struct i2c_adapter *adap)
+{
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm ki2c_algo = {
+ .master_xfer = ki2c_xfer,
+ .functionality = ki2c_func,
+};
+
+static int ki2c_probe(struct auxiliary_device *auxdev,
+ const struct auxiliary_device_id *id)
+{
+ struct device *dev = &auxdev->dev;
+ struct i2c_adapter *adap;
+ struct ki2c *ki2c;
+ int ret;
+
+ ki2c = devm_kzalloc(dev, sizeof(*ki2c), GFP_KERNEL);
+ if (!ki2c)
+ return -ENOMEM;
+ ki2c->auxdev = container_of(auxdev, struct keba_i2c_auxdev, auxdev);
+ ki2c->client = devm_kcalloc(dev, ki2c->auxdev->info_size,
+ sizeof(*ki2c->client), GFP_KERNEL);
+ if (!ki2c->client)
+ return -ENOMEM;
+ ki2c->client_size = ki2c->auxdev->info_size;
+ auxiliary_set_drvdata(auxdev, ki2c);
+
+ ki2c->base = devm_ioremap_resource(dev, &ki2c->auxdev->io);
+ if (IS_ERR(ki2c->base))
+ return PTR_ERR(ki2c->base);
+
+ adap = &ki2c->adapter;
+ strscpy(adap->name, "KEBA I2C adapter", sizeof(adap->name));
+ adap->owner = THIS_MODULE;
+ adap->class = I2C_CLASS_HWMON;
+ adap->algo = &ki2c_algo;
+ adap->dev.parent = dev;
+
+ i2c_set_adapdata(adap, ki2c);
+
+ /* enable controller */
+ iowrite8(KI2C_CONTROL_MEN, ki2c->base + KI2C_CONTROL_REG);
+
+ /* reset bus before probing I2C devices */
+ ret = ki2c_reset_bus(ki2c);
+ if (ret)
+ goto out;
+
+ ret = devm_i2c_add_adapter(dev, adap);
+ if (ret) {
+ dev_err(dev, "Failed to add adapter (%d)!\n", ret);
+ goto out;
+ }
+
+ ret = ki2c_register_devices(ki2c);
+ if (ret) {
+ dev_err(dev, "Failed to register devices (%d)!\n", ret);
+ goto out;
+ }
+
+ return 0;
+
+out:
+ iowrite8(KI2C_CONTROL_DISABLE, ki2c->base + KI2C_CONTROL_REG);
+ return ret;
+}
+
+static void ki2c_remove(struct auxiliary_device *auxdev)
+{
+ struct ki2c *ki2c = auxiliary_get_drvdata(auxdev);
+
+ ki2c_unregister_devices(ki2c);
+
+ /* disable controller */
+ iowrite8(KI2C_CONTROL_DISABLE, ki2c->base + KI2C_CONTROL_REG);
+
+ auxiliary_set_drvdata(auxdev, NULL);
+}
+
+static const struct auxiliary_device_id ki2c_devtype_aux[] = {
+ { .name = "keba.i2c" },
+ { },
+};
+MODULE_DEVICE_TABLE(auxiliary, ki2c_devtype_aux);
+
+static struct auxiliary_driver ki2c_driver_aux = {
+ .name = KI2C,
+ .id_table = ki2c_devtype_aux,
+ .probe = ki2c_probe,
+ .remove = ki2c_remove,
+};
+module_auxiliary_driver(ki2c_driver_aux);
+
+MODULE_AUTHOR("Gerhard Engleder <eg@keba.com>");
+MODULE_DESCRIPTION("KEBA I2C bus controller driver");
+MODULE_LICENSE("GPL");
--
2.39.2