[PATCH] i2c/busses: Add i2c-icy for I2C on m68k/Amiga

Max Staudt
2019-08-20T09:27:39Z

This is the i2c-icy driver for the ICY board for Amiga computers.
It connects a PCF8584 I2C controller to the Zorro bus, providing I2C
connectivity. The original documentation can be found on Aminet:

https://aminet.net/package/docs/hard/icy

IRQ support is currently not implemented, as i2c-algo-pcf is built for
the ISA bus and a straight implementation of the same stack locks up a
Zorro machine.

v5: usleep_range() instead of udelay()
Style

v3: Fixed %pa format string
Dropped adapter class.
Clarified licence.
Removed clock parameter.

v2: Matched function names to callbacks from i2c-algo-pcf
Used z_readb()/z_writeb()
Removed BROKEN_ON_SMP in Kconfig
Moved LTC2990 to a separate commit

Signed-off-by: Max Staudt <max@enpas.org>
---
MAINTAINERS | 6 ++
drivers/i2c/busses/Kconfig | 11 +++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-icy.c | 172 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 190 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-icy.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 1be025959..70336c083 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7705,6 +7705,12 @@ S: Maintained
F: drivers/mfd/lpc_ich.c
F: drivers/gpio/gpio-ich.c

+ICY I2C DRIVER
+M: Max Staudt <max@enpas.org>
+L: linux-i2c@vger.kernel.org
+S: Maintained
+F: drivers/i2c/busses/i2c-icy.c
+
IDE SUBSYSTEM
M: "David S. Miller" <davem@davemloft.net>
L: linux-ide@vger.kernel.org
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index ee5dfb5ae..9e57e1101 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -1300,6 +1300,17 @@ config I2C_ELEKTOR
This support is also available as a module. If so, the module
will be called i2c-elektor.

+config I2C_ICY
+ tristate "ICY Zorro card"
+ depends on ZORRO
+ select I2C_ALGOPCF
+ help
+ This supports the PCF8584 Zorro bus I2C adapter, known as ICY.
+ Say Y if you own such an adapter.
+
+ This support is also available as a module. If so, the module
+ will be called i2c-icy.
+
config I2C_MLXCPLD
tristate "Mellanox I2C driver"
depends on X86_64
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index a3245231b..d0e1c3d4e 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -139,6 +139,7 @@ obj-$(CONFIG_I2C_BCM_KONA) += i2c-bcm-kona.o
obj-$(CONFIG_I2C_BRCMSTB) += i2c-brcmstb.o
obj-$(CONFIG_I2C_CROS_EC_TUNNEL) += i2c-cros-ec-tunnel.o
obj-$(CONFIG_I2C_ELEKTOR) += i2c-elektor.o
+obj-$(CONFIG_I2C_ICY) += i2c-icy.o
obj-$(CONFIG_I2C_MLXCPLD) += i2c-mlxcpld.o
obj-$(CONFIG_I2C_OPAL) += i2c-opal.o
obj-$(CONFIG_I2C_PCA_ISA) += i2c-pca-isa.o
diff --git a/drivers/i2c/busses/i2c-icy.c b/drivers/i2c/busses/i2c-icy.c
new file mode 100644
index 000000000..7b7083da8
--- /dev/null
+++ b/drivers/i2c/busses/i2c-icy.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * I2C driver for stand-alone PCF8584 style adapters on Zorro cards
+ *
+ * Original ICY documentation can be found on Aminet:
+ * https://aminet.net/package/docs/hard/icy
+ *
+ * There has been a modern community re-print of this design in 2019:
+ * https://www.a1k.org/forum/index.php?threads/70106/
+ *
+ * The card is basically a Philips PCF8584 connected straight to the
+ * beginning of the AutoConfig'd address space (register S1 on base+2),
+ * with /INT on /INT2 on the Zorro bus.
+ *
+ * Copyright (c) 2019 Max Staudt <max@enpas.org>
+ *
+ * This started as a fork of i2c-elektor.c and has evolved since.
+ * Thanks go to its authors for providing a base to grow on.
+ *
+ *
+ * IRQ support is currently not implemented.
+ *
+ * As it turns out, i2c-algo-pcf is really written with i2c-elektor's
+ * edge-triggered ISA interrupts in mind, while the Amiga's Zorro bus has
+ * level-triggered interrupts. This means that once an interrupt occurs, we
+ * have to tell the PCF8584 to shut up immediately, or it will keep the
+ * interrupt line busy and cause an IRQ storm.
+
+ * However, because of the PCF8584's host-side protocol, there is no good
+ * way to just quieten it without side effects. Rather, we have to perform
+ * the next read/write operation straight away, which will reset the /INT
+ * pin. This entails re-designing the core of i2c-algo-pcf in the future.
+ * For now, we never request an IRQ from the PCF8584, and poll it instead.
+ */
+
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <linux/i2c.h>
+#include <linux/i2c-algo-pcf.h>
+
+#include <asm/amigaints.h>
+#include <linux/zorro.h>
+
+#include "../algos/i2c-algo-pcf.h"
+
+struct icy_i2c {
+ struct i2c_adapter adapter;
+
+ void __iomem *reg_s0;
+ void __iomem *reg_s1;
+};
+
+/*
+ * Functions called by i2c-algo-pcf
+ */
+static void icy_pcf_setpcf(void *data, int ctl, int val)
+{
+ struct icy_i2c *i2c = (struct icy_i2c *)data;
+
+ u8 __iomem *address = ctl ? i2c->reg_s1 : i2c->reg_s0;
+
+ z_writeb(val, address);
+}
+
+static int icy_pcf_getpcf(void *data, int ctl)
+{
+ struct icy_i2c *i2c = (struct icy_i2c *)data;
+
+ u8 __iomem *address = ctl ? i2c->reg_s1 : i2c->reg_s0;
+ return z_readb(address);
+}
+
+static int icy_pcf_getown(void *data)
+{
+ return 0x55;
+}
+
+static int icy_pcf_getclock(void *data)
+{
+ return 0x1c;
+}
+
+static void icy_pcf_waitforpin(void *data)
+{
+ usleep_range(50, 150);
+}
+
+/*
+ * Main i2c-icy part
+ */
+static int icy_probe(struct zorro_dev *z,
+ const struct zorro_device_id *ent)
+{
+ struct icy_i2c *i2c;
+ struct i2c_algo_pcf_data *algo_data;
+
+ i2c = devm_kzalloc(&z->dev, sizeof(*i2c), GFP_KERNEL);
+ if (!i2c)
+ return -ENOMEM;
+
+ algo_data = devm_kzalloc(&z->dev, sizeof(*algo_data), GFP_KERNEL);
+ if (!algo_data)
+ return -ENOMEM;
+
+ dev_set_drvdata(&z->dev, i2c);
+ i2c->adapter.dev.parent = &z->dev;
+ i2c->adapter.owner = THIS_MODULE;
+ /* i2c->adapter.algo assigned by i2c_pcf_add_bus() */
+ i2c->adapter.algo_data = algo_data;
+ strlcpy(i2c->adapter.name, "ICY I2C Zorro adapter",
+ sizeof(i2c->adapter.name));
+
+ if (!devm_request_mem_region(&z->dev,
+ z->resource.start,
+ 4, i2c->adapter.name))
+ return -ENXIO;
+
+ /* Driver private data */
+ i2c->reg_s0 = ZTWO_VADDR(z->resource.start);
+ i2c->reg_s1 = ZTWO_VADDR(z->resource.start + 2);
+
+ algo_data->data = i2c;
+ algo_data->setpcf = icy_pcf_setpcf;
+ algo_data->getpcf = icy_pcf_getpcf;
+ algo_data->getown = icy_pcf_getown;
+ algo_data->getclock = icy_pcf_getclock;
+ algo_data->waitforpin = icy_pcf_waitforpin;
+
+ if (i2c_pcf_add_bus(&i2c->adapter)) {
+ dev_err(&z->dev, "i2c_pcf_add_bus() failed\n");
+ return -ENXIO;
+ }
+
+ dev_info(&z->dev, "ICY I2C controller at %pa, IRQ not implemented\n",
+ &z->resource.start);
+
+ return 0;
+}
+
+static void icy_remove(struct zorro_dev *z)
+{
+ struct icy_i2c *i2c = dev_get_drvdata(&z->dev);
+
+ i2c_del_adapter(&i2c->adapter);
+}
+
+static const struct zorro_device_id icy_zorro_tbl[] = {
+ { ZORRO_ID(VMC, 15, 0), },
+ { 0 }
+};
+
+MODULE_DEVICE_TABLE(zorro, icy_zorro_tbl);
+
+static struct zorro_driver icy_driver = {
+ .name = "i2c-icy",
+ .id_table = icy_zorro_tbl,
+ .probe = icy_probe,
+ .remove = icy_remove,
+};
+
+module_driver(icy_driver,
+ zorro_register_driver,
+ zorro_unregister_driver);
+
+MODULE_AUTHOR("Max Staudt <max@enpas.org>");
+MODULE_DESCRIPTION("I2C bus via PCF8584 on ICY Zorro card");
+MODULE_LICENSE("GPL v2");
--
2.11.0