i2c-nforce2: Add support for multiplexing on the Tyan S4985
Just like the Tyan S4882, the S4985 uses a multiplexer to give access
to all 16 memory module SPD EEPROMs. This specific i2c-nforce2-s4985
driver adds support for this. It is heavily based on the older
i2c-amd756-s4882 driver.
As more mainboards will use multiplexer chips, we will have to find a
way to support them without having to write a new specfic driver for
each. The recent changes to the i2c subsystem should help us, and the
new gpio subsystem might help, too.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/i2c/busses/i2c-nforce2-s4985.c b/drivers/i2c/busses/i2c-nforce2-s4985.c
new file mode 100644
index 0000000..6a8995d
--- /dev/null
+++ b/drivers/i2c/busses/i2c-nforce2-s4985.c
@@ -0,0 +1,257 @@
+/*
+ * i2c-nforce2-s4985.c - i2c-nforce2 extras for the Tyan S4985 motherboard
+ *
+ * Copyright (C) 2008 Jean Delvare <khali@linux-fr.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/*
+ * We select the channels by sending commands to the Philips
+ * PCA9556 chip at I2C address 0x18. The main adapter is used for
+ * the non-multiplexed part of the bus, and 4 virtual adapters
+ * are defined for the multiplexed addresses: 0x50-0x53 (memory
+ * module EEPROM) located on channels 1-4. We define one virtual
+ * adapter per CPU, which corresponds to one multiplexed channel:
+ * CPU0: virtual adapter 1, channel 1
+ * CPU1: virtual adapter 2, channel 2
+ * CPU2: virtual adapter 3, channel 3
+ * CPU3: virtual adapter 4, channel 4
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+
+extern struct i2c_adapter *nforce2_smbus;
+
+static struct i2c_adapter *s4985_adapter;
+static struct i2c_algorithm *s4985_algo;
+
+/* Wrapper access functions for multiplexed SMBus */
+static DEFINE_MUTEX(nforce2_lock);
+
+static s32 nforce2_access_virt0(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ int error;
+
+ /* We exclude the multiplexed addresses */
+ if ((addr & 0xfc) == 0x50 || (addr & 0xfc) == 0x30
+ || addr == 0x18)
+ return -ENXIO;
+
+ mutex_lock(&nforce2_lock);
+ error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
+ command, size, data);
+ mutex_unlock(&nforce2_lock);
+
+ return error;
+}
+
+/* We remember the last used channels combination so as to only switch
+ channels when it is really needed. This greatly reduces the SMBus
+ overhead, but also assumes that nobody will be writing to the PCA9556
+ in our back. */
+static u8 last_channels;
+
+static inline s32 nforce2_access_channel(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data,
+ u8 channels)
+{
+ int error;
+
+ /* We exclude the non-multiplexed addresses */
+ if ((addr & 0xfc) != 0x50 && (addr & 0xfc) != 0x30)
+ return -ENXIO;
+
+ mutex_lock(&nforce2_lock);
+ if (last_channels != channels) {
+ union i2c_smbus_data mplxdata;
+ mplxdata.byte = channels;
+
+ error = nforce2_smbus->algo->smbus_xfer(adap, 0x18, 0,
+ I2C_SMBUS_WRITE, 0x01,
+ I2C_SMBUS_BYTE_DATA,
+ &mplxdata);
+ if (error)
+ goto UNLOCK;
+ last_channels = channels;
+ }
+ error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
+ command, size, data);
+
+UNLOCK:
+ mutex_unlock(&nforce2_lock);
+ return error;
+}
+
+static s32 nforce2_access_virt1(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ /* CPU0: channel 1 enabled */
+ return nforce2_access_channel(adap, addr, flags, read_write, command,
+ size, data, 0x02);
+}
+
+static s32 nforce2_access_virt2(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ /* CPU1: channel 2 enabled */
+ return nforce2_access_channel(adap, addr, flags, read_write, command,
+ size, data, 0x04);
+}
+
+static s32 nforce2_access_virt3(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ /* CPU2: channel 3 enabled */
+ return nforce2_access_channel(adap, addr, flags, read_write, command,
+ size, data, 0x08);
+}
+
+static s32 nforce2_access_virt4(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ /* CPU3: channel 4 enabled */
+ return nforce2_access_channel(adap, addr, flags, read_write, command,
+ size, data, 0x10);
+}
+
+static int __init nforce2_s4985_init(void)
+{
+ int i, error;
+ union i2c_smbus_data ioconfig;
+
+ /* Unregister physical bus */
+ if (!nforce2_smbus)
+ return -ENODEV;
+ error = i2c_del_adapter(nforce2_smbus);
+ if (error) {
+ dev_err(&nforce2_smbus->dev, "Physical bus removal failed\n");
+ goto ERROR0;
+ }
+
+ printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4985\n");
+ /* Define the 5 virtual adapters and algorithms structures */
+ s4985_adapter = kzalloc(5 * sizeof(struct i2c_adapter), GFP_KERNEL);
+ if (!s4985_adapter) {
+ error = -ENOMEM;
+ goto ERROR1;
+ }
+ s4985_algo = kzalloc(5 * sizeof(struct i2c_algorithm), GFP_KERNEL);
+ if (!s4985_algo) {
+ error = -ENOMEM;
+ goto ERROR2;
+ }
+
+ /* Fill in the new structures */
+ s4985_algo[0] = *(nforce2_smbus->algo);
+ s4985_algo[0].smbus_xfer = nforce2_access_virt0;
+ s4985_adapter[0] = *nforce2_smbus;
+ s4985_adapter[0].algo = s4985_algo;
+ s4985_adapter[0].dev.parent = nforce2_smbus->dev.parent;
+ for (i = 1; i < 5; i++) {
+ s4985_algo[i] = *(nforce2_smbus->algo);
+ s4985_adapter[i] = *nforce2_smbus;
+ snprintf(s4985_adapter[i].name, sizeof(s4985_adapter[i].name),
+ "SMBus nForce2 adapter (CPU%d)", i - 1);
+ s4985_adapter[i].algo = s4985_algo + i;
+ s4985_adapter[i].dev.parent = nforce2_smbus->dev.parent;
+ }
+ s4985_algo[1].smbus_xfer = nforce2_access_virt1;
+ s4985_algo[2].smbus_xfer = nforce2_access_virt2;
+ s4985_algo[3].smbus_xfer = nforce2_access_virt3;
+ s4985_algo[4].smbus_xfer = nforce2_access_virt4;
+
+ /* Configure the PCA9556 multiplexer */
+ ioconfig.byte = 0x00; /* All I/O to output mode */
+ error = nforce2_smbus->algo->smbus_xfer(nforce2_smbus, 0x18, 0,
+ I2C_SMBUS_WRITE, 0x03,
+ I2C_SMBUS_BYTE_DATA, &ioconfig);
+ if (error) {
+ dev_err(&nforce2_smbus->dev, "PCA9556 configuration failed\n");
+ error = -EIO;
+ goto ERROR3;
+ }
+
+ /* Register virtual adapters */
+ for (i = 0; i < 5; i++) {
+ error = i2c_add_adapter(s4985_adapter + i);
+ if (error) {
+ dev_err(&nforce2_smbus->dev,
+ "Virtual adapter %d registration "
+ "failed, module not inserted\n", i);
+ for (i--; i >= 0; i--)
+ i2c_del_adapter(s4985_adapter + i);
+ goto ERROR3;
+ }
+ }
+
+ return 0;
+
+ERROR3:
+ kfree(s4985_algo);
+ s4985_algo = NULL;
+ERROR2:
+ kfree(s4985_adapter);
+ s4985_adapter = NULL;
+ERROR1:
+ /* Restore physical bus */
+ i2c_add_adapter(nforce2_smbus);
+ERROR0:
+ return error;
+}
+
+static void __exit nforce2_s4985_exit(void)
+{
+ if (s4985_adapter) {
+ int i;
+
+ for (i = 0; i < 5; i++)
+ i2c_del_adapter(s4985_adapter+i);
+ kfree(s4985_adapter);
+ s4985_adapter = NULL;
+ }
+ kfree(s4985_algo);
+ s4985_algo = NULL;
+
+ /* Restore physical bus */
+ if (i2c_add_adapter(nforce2_smbus))
+ dev_err(&nforce2_smbus->dev, "Physical bus restoration "
+ "failed\n");
+}
+
+MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
+MODULE_DESCRIPTION("S4985 SMBus multiplexing");
+MODULE_LICENSE("GPL");
+
+module_init(nforce2_s4985_init);
+module_exit(nforce2_s4985_exit);