[PATCH linux dev-4.13] drivers: i2c: master arbiter: create driver
Joel Stanley
joel at jms.id.au
Thu Mar 8 16:34:30 AEDT 2018
On Thu, Mar 8, 2018 at 3:36 PM, ChenKenYY 陳永營 TAO
<chen.kenyy at inventec.com> wrote:
> Hi Joel,
>
> Sure, I can take it, but I need some instructions on the next action.
Okay. I suggest you download the patch from patchwork and apply it to
the latest kernel release, 4.16-rc4:
https://patchwork.ozlabs.org/patch/726491/
You can download it by clicking the 'mbox' link at the top right of the page.
Now you will have a file called
RFC-i2c-mux-Driver-for-PCA9641-I2C-Master-Arbiter.patch.
$ git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
$ cd linux
$ git checkout -b pca9641-mux v4.16-rc4
$ git am ~/Downloads/RFC-i2c-mux-Driver-for-PCA9641-I2C-Master-Arbiter.patch
>From there, take a look at the comments on the two reviews that Vidya had:
https://patchwork.ozlabs.org/patch/726491/#1580479
https://patchwork.ozlabs.org/patch/726491/#1582916
Fix those issues, and add your signed off by:
$ git add drivers/i2c/muxes/i2c-mux-pca9541.c
$ git commit --amend -s
Then test this driver on your board. To do this, modify the device
tree. You should be able to do this by modifying the ast2500-evb
device tree, and boot that on your system.
Once this is working, use the checkpatch.pl tool to check for common mistakes:
$ ./scripts/checkpatch.pl drivers/i2c/muxes/i2c-mux-pca9541.c
Then use get_maintainer.pl to get a list of people you should send the patch to:
$ ./scripts/get_maintainer.pl -f drivers/i2c/muxes/i2c-mux-pca9541.c
Guenter Roeck <linux at roeck-us.net> (maintainer:PCA9541 I2C BUS MASTER
SELECTOR DRIVER)
Peter Rosin <peda at axentia.se> (maintainer:I2C MUXES)
Wolfram Sang <wsa at the-dreams.de> (maintainer:I2C SUBSYSTEM)
linux-i2c at vger.kernel.org (open list:PCA9541 I2C BUS MASTER SELECTOR DRIVER)
linux-kernel at vger.kernel.org (open list)
In addition, please add me to this list so I can help. Then send the
patch out, with a comment in the commit message (below the ---) that
you have continued this work from the previous author, and have tested
it on your system.
Cheers,
Joel
>
> Thanks,
> Ken
>
> 2018-03-08 11:02 GMT+08:00 Joel Stanley <joel at jms.id.au>:
>> Hello Ken,
>>
>> On Fri, Feb 23, 2018 at 3:52 PM, Ken Chen <chen.kenyy at inventec.com> wrote:
>>> Initial PCA9641 2 chennel I2C bus master arbiter
>>>
>>> Signed-off-by: Ken Chen <chen.kenyy at inventec.com>
>>
>> The code here looks good. I did some searching, and found that someone
>> submitted a driver for this part about a year ago:
>>
>> https://patchwork.ozlabs.org/patch/726491/
>>
>> Unfortunately the submitter did not send another version after it was
>> reviewed. I suggest we take up the patch that was submitted, make the
>> changes suggested, and submit it upstream. Are you able to take on
>> that work?
>>
>> Cheers,
>>
>> Joel
>>
>>> ---
>>> drivers/i2c/muxes/Kconfig | 9 +
>>> drivers/i2c/muxes/Makefile | 1 +
>>> drivers/i2c/muxes/i2c-mux-pca9641.c | 372 ++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 382 insertions(+)
>>> create mode 100644 drivers/i2c/muxes/i2c-mux-pca9641.c
>>>
>>> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
>>> index 1712132..1cd1ad3 100644
>>> --- a/drivers/i2c/muxes/Kconfig
>>> +++ b/drivers/i2c/muxes/Kconfig
>>> @@ -73,6 +73,15 @@ config I2C_MUX_PCA954x
>>> This driver can also be built as a module. If so, the module
>>> will be called i2c-mux-pca954x.
>>>
>>> +config I2C_MUX_PCA9641
>>> + tristate "NXP PCA9641 I2C Master demultiplexer"
>>> + help
>>> + If you say yes here you get support for the NXP PCA9641
>>> + I2C Master demultiplexer with an arbiter function.
>>> +
>>> + This driver can also be built as a module. If so, the module
>>> + will be called i2c-mux-pca9641.
>>> +
>>> config I2C_MUX_PINCTRL
>>> tristate "pinctrl-based I2C multiplexer"
>>> depends on PINCTRL
>>> diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
>>> index 4a67d31..f95d5f5 100644
>>> --- a/drivers/i2c/muxes/Makefile
>>> +++ b/drivers/i2c/muxes/Makefile
>>> @@ -11,6 +11,7 @@ obj-$(CONFIG_I2C_MUX_LTC4306) += i2c-mux-ltc4306.o
>>> obj-$(CONFIG_I2C_MUX_MLXCPLD) += i2c-mux-mlxcpld.o
>>> obj-$(CONFIG_I2C_MUX_PCA9541) += i2c-mux-pca9541.o
>>> obj-$(CONFIG_I2C_MUX_PCA954x) += i2c-mux-pca954x.o
>>> +obj-$(CONFIG_I2C_MUX_PCA9641) += i2c-mux-pca9641.o
>>> obj-$(CONFIG_I2C_MUX_PINCTRL) += i2c-mux-pinctrl.o
>>> obj-$(CONFIG_I2C_MUX_REG) += i2c-mux-reg.o
>>>
>>> diff --git a/drivers/i2c/muxes/i2c-mux-pca9641.c b/drivers/i2c/muxes/i2c-mux-pca9641.c
>>> new file mode 100644
>>> index 0000000..ca7b816
>>> --- /dev/null
>>> +++ b/drivers/i2c/muxes/i2c-mux-pca9641.c
>>> @@ -0,0 +1,372 @@
>>> +/*
>>> + * I2C demultiplexer driver for PCA9641 bus master demultiplexer
>>> + *
>>> + * Copyright (c) 2010 Ericsson AB.
>>> + *
>>> + * Author: Ken Chen <chen.kenyy at inventec.com>
>>> + *
>>> + * Derived from:
>>> + *
>>> + * This file is licensed under the terms of the GNU General Public
>>> + * License version 2. This program is licensed "as is" without any
>>> + * warranty of any kind, whether express or implied.
>>> + */
>>> +
>>> +#include <linux/module.h>
>>> +#include <linux/jiffies.h>
>>> +#include <linux/delay.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/device.h>
>>> +#include <linux/i2c.h>
>>> +#include <linux/i2c-mux.h>
>>> +
>>> +#include <linux/i2c/pca954x.h>
>>> +
>>> +/*
>>> + * The PCA9641 is two I2C bus masters demultiplexer. It supports two I2C masters
>>> + * connected to a single slave bus.
>>> + *
>>> + * It is designed for high reliability dual master I2C bus applications where
>>> + * correct system operation is required, even when two I2C master issue their
>>> + * commands at the same time. The arbiter will select a winner and let it work
>>> + * uninterrupted, and the losing master will take control of the I2C bus after
>>> + * the winnter has finished. The arbiter also allows for queued requests where
>>> + * a master requests the downstream bus while the other master has control.
>>> + *
>>> + */
>>> +
>>> +#define PCA9641_ID 0x01
>>> +#define PCA9641_ID_MAGIC 0x38
>>> +
>>> +#define PCA9641_CONTROL 0x01
>>> +#define PCA9641_STATUS 0x02
>>> +#define PCA9641_TIME 0x03
>>> +
>>> +#define PCA9641_CTL_LOCK_REQ (1 << 0)
>>> +#define PCA9641_CTL_LOCK_GRANT (1 << 1)
>>> +#define PCA9641_CTL_BUS_CONNECT (1 << 2)
>>> +#define PCA9641_CTL_BUS_INIT (1 << 3)
>>> +#define PCA9641_CTL_SMBUS_SWRST (1 << 4)
>>> +#define PCA9641_CTL_IDLE_TIMER_DIS (1 << 5)
>>> +#define PCA9641_CTL_SMBUS_DIS (1 << 6)
>>> +#define PCA9641_CTL_PRIORITY (1 << 7)
>>> +
>>> +#define PCA9641_STS_OTHER_LOCK (1 << 0)
>>> +#define PCA9641_STS_BUS_INIT_FAIL (1 << 1)
>>> +#define PCA9641_STS_BUS_HUNG (1 << 2)
>>> +#define PCA9641_STS_MBOX_EMPTY (1 << 3)
>>> +#define PCA9641_STS_MBOX_FULL (1 << 4)
>>> +#define PCA9641_STS_TEST_INT (1 << 5)
>>> +#define PCA9641_STS_SCL_IO (1 << 6)
>>> +#define PCA9641_STS_SDA_IO (1 << 7)
>>> +
>>> +#define PCA9641_RES_TIME 0x03
>>> +
>>> +#define other_lock(x) ((x) & PCA9641_STS_OTHER_LOCK)
>>> +#define lock_grant(x) ((x) & PCA9641_CTL_LOCK_GRANT)
>>> +
>>> +/* arbitration timeouts, in jiffies */
>>> +#define ARB_TIMEOUT (HZ / 8) /* 125 ms until forcing bus ownership */
>>> +#define ARB2_TIMEOUT (HZ / 4) /* 250 ms until acquisition failure */
>>> +
>>> +/* arbitration retry delays, in us */
>>> +#define SELECT_DELAY_SHORT 50
>>> +#define SELECT_DELAY_LONG 1000
>>> +
>>> +struct pca9641 {
>>> + struct i2c_client *client;
>>> + unsigned long select_timeout;
>>> + unsigned long arb_timeout;
>>> +};
>>> +
>>> +static const struct i2c_device_id pca9641_id[] = {
>>> + {"pca9641", 0},
>>> + {}
>>> +};
>>> +
>>> +MODULE_DEVICE_TABLE(i2c, pca9641_id);
>>> +
>>> +#ifdef CONFIG_OF
>>> +static const struct of_device_id pca9641_of_match[] = {
>>> + { .compatible = "nxp,pca9641" },
>>> + {}
>>> +};
>>> +#endif
>>> +
>>> +/*
>>> + * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
>>> + * as they will try to lock the adapter a second time.
>>> + */
>>> +static int pca9641_reg_write(struct i2c_client *client, u8 command, u8 val)
>>> +{
>>> + struct i2c_adapter *adap = client->adapter;
>>> + int ret;
>>> +
>>> + if (adap->algo->master_xfer) {
>>> + struct i2c_msg msg;
>>> + char buf[2];
>>> +
>>> + msg.addr = client->addr;
>>> + msg.flags = 0;
>>> + msg.len = 2;
>>> + buf[0] = command;
>>> + buf[1] = val;
>>> + msg.buf = buf;
>>> + ret = __i2c_transfer(adap, &msg, 1);
>>> + } else {
>>> + union i2c_smbus_data data;
>>> +
>>> + data.byte = val;
>>> + ret = adap->algo->smbus_xfer(adap, client->addr,
>>> + client->flags,
>>> + I2C_SMBUS_WRITE,
>>> + command,
>>> + I2C_SMBUS_BYTE_DATA, &data);
>>> + }
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +/*
>>> + * Read from chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
>>> + * as they will try to lock adapter a second time.
>>> + */
>>> +static int pca9641_reg_read(struct i2c_client *client, u8 command)
>>> +{
>>> + struct i2c_adapter *adap = client->adapter;
>>> + int ret;
>>> + u8 val;
>>> +
>>> + if (adap->algo->master_xfer) {
>>> + struct i2c_msg msg[2] = {
>>> + {
>>> + .addr = client->addr,
>>> + .flags = 0,
>>> + .len = 1,
>>> + .buf = &command
>>> + },
>>> + {
>>> + .addr = client->addr,
>>> + .flags = I2C_M_RD,
>>> + .len = 1,
>>> + .buf = &val
>>> + }
>>> + };
>>> + ret = __i2c_transfer(adap, msg, 2);
>>> + if (ret == 2)
>>> + ret = val;
>>> + else if (ret >= 0)
>>> + ret = -EIO;
>>> + } else {
>>> + union i2c_smbus_data data;
>>> +
>>> + ret = adap->algo->smbus_xfer(adap, client->addr,
>>> + client->flags,
>>> + I2C_SMBUS_READ,
>>> + command,
>>> + I2C_SMBUS_BYTE_DATA, &data);
>>> + if (!ret)
>>> + ret = data.byte;
>>> + }
>>> + return ret;
>>> +}
>>> +
>>> +/*
>>> + * Arbitration management functions
>>> + */
>>> +static void pca9641_release_bus(struct i2c_client *client)
>>> +{
>>> + int reg;
>>> +
>>> + pca9641_reg_write(client, PCA9641_CONTROL, 0);
>>> +}
>>> +
>>> +/*
>>> + * Channel arbitration
>>> + *
>>> + * Return values:
>>> + * <0: error
>>> + * 0 : bus not acquired
>>> + * 1 : bus acquired
>>> + */
>>> +static int pca9641_arbitrate(struct i2c_client *client)
>>> +{
>>> + struct i2c_mux_core *muxc = i2c_get_clientdata(client);
>>> + struct pca9641 *data = i2c_mux_priv(muxc);
>>> + int reg_ctl, reg_sts;
>>> +
>>> + reg_ctl = pca9641_reg_read(client, PCA9641_CONTROL);
>>> + if (reg_ctl < 0)
>>> + return reg_ctl;
>>> + reg_sts = pca9641_reg_read(client, PCA9641_STATUS);
>>> +
>>> + if (!other_lock(reg_sts) && !lock_grant(reg_ctl)) {
>>> + /*
>>> + * Bus is off. Request ownership or turn it on unless
>>> + * other master requested ownership.
>>> + */
>>> + reg_ctl |= PCA9641_CTL_LOCK_REQ;
>>> + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl);
>>> +
>>> + udelay(100);
>>> +
>>> + reg_ctl = pca9641_reg_read(client, PCA9641_CONTROL);
>>> +
>>> + if (lock_grant(reg_ctl)) {
>>> + /*
>>> + * Other master did not request ownership,
>>> + * or arbitration timeout expired. Take the bus.
>>> + */
>>> + reg_ctl |= PCA9641_CTL_BUS_CONNECT | PCA9641_CTL_LOCK_REQ;
>>> + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl);
>>> + data->select_timeout = SELECT_DELAY_SHORT;
>>> +
>>> + return 1;
>>> + } else {
>>> + /*
>>> + * Other master requested ownership.
>>> + * Set extra long timeout to give it time to acquire it.
>>> + */
>>> + data->select_timeout = SELECT_DELAY_LONG * 2;
>>> + }
>>> + } else if (lock_grant(reg_ctl)) {
>>> + /*
>>> + * Bus is on, and we own it. We are done with acquisition.
>>> + */
>>> + reg_ctl |= PCA9641_CTL_BUS_CONNECT | PCA9641_CTL_LOCK_REQ;
>>> + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl);
>>> +
>>> + return 1;
>>> + } else if (other_lock(reg_sts)) {
>>> + /*
>>> + * Other master owns the bus.
>>> + * If arbitration timeout has expired, force ownership.
>>> + * Otherwise request it.
>>> + */
>>> + data->select_timeout = SELECT_DELAY_LONG;
>>> + reg_ctl |= PCA9641_CTL_LOCK_REQ;
>>> + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl);
>>> +
>>> + /*
>>> + * if (time_is_before_eq_jiffies(data->arb_timeout)) {
>>> + * TODO:Time is up, take the bus and reset it.
>>> + *
>>> + *} else {
>>> + * TODO: Request bus ownership if needed
>>> + *
>>> + *}
>>> + */
>>> + }
>>> + return 0;
>>> +}
>>> +
>>> +static int pca9641_select_chan(struct i2c_mux_core *muxc, u32 chan)
>>> +{
>>> + struct pca9641 *data = i2c_mux_priv(muxc);
>>> + struct i2c_client *client = data->client;
>>> + int ret;
>>> + unsigned long timeout = jiffies + ARB2_TIMEOUT;
>>> + /* give up after this time */
>>> +
>>> + data->arb_timeout = jiffies + ARB_TIMEOUT;
>>> + /* force bus ownership after this time */
>>> +
>>> + do {
>>> + ret = pca9641_arbitrate(client);
>>> + if (ret)
>>> + return ret < 0 ? ret : 0;
>>> +
>>> + if (data->select_timeout == SELECT_DELAY_SHORT)
>>> + udelay(data->select_timeout);
>>> + else
>>> + msleep(data->select_timeout / 1000);
>>> + } while (time_is_after_eq_jiffies(timeout));
>>> +
>>> + return -ETIMEDOUT;
>>> +}
>>> +
>>> +static int pca9641_release_chan(struct i2c_mux_core *muxc, u32 chan)
>>> +{
>>> + struct pca9641 *data = i2c_mux_priv(muxc);
>>> + struct i2c_client *client = data->client;
>>> +
>>> + pca9641_release_bus(client);
>>> + return 0;
>>> +}
>>> +
>>> +/*
>>> + * I2C init/probing/exit functions
>>> + */
>>> +static int pca9641_probe(struct i2c_client *client,
>>> + const struct i2c_device_id *id)
>>> +{
>>> + struct i2c_adapter *adap = client->adapter;
>>> + struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev);
>>> + struct i2c_mux_core *muxc;
>>> + struct pca9641 *data;
>>> + int force;
>>> + int ret;
>>> +
>>> + if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA))
>>> + return -ENODEV;
>>> +
>>> + /*
>>> + * I2C accesses are unprotected here.
>>> + * We have to lock the adapter before releasing the bus.
>>> + */
>>> + i2c_lock_adapter(adap);
>>> + pca9641_release_bus(client);
>>> + i2c_unlock_adapter(adap);
>>> +
>>> + /* Create mux adapter */
>>> +
>>> + force = 0;
>>> + if (pdata)
>>> + force = pdata->modes[0].adap_id;
>>> + muxc = i2c_mux_alloc(adap, &client->dev, 8, sizeof(*data),
>>> + I2C_MUX_ARBITRATOR,
>>> + pca9641_select_chan, pca9641_release_chan);
>>> + if (!muxc)
>>> + return -ENOMEM;
>>> +
>>> + data = i2c_mux_priv(muxc);
>>> + data->client = client;
>>> +
>>> + i2c_set_clientdata(client, muxc);
>>> +
>>> +
>>> + ret = i2c_mux_add_adapter(muxc, force, 0, 0);
>>> + if (ret) {
>>> + dev_err(&client->dev, "failed to register master demultiplexer\n");
>>> + return ret;
>>> + }
>>> +
>>> + dev_info(&client->dev, "registered master demultiplexer for I2C %s\n",
>>> + client->name);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int pca9641_remove(struct i2c_client *client)
>>> +{
>>> + struct i2c_mux_core *muxc = i2c_get_clientdata(client);
>>> +
>>> + i2c_mux_del_adapters(muxc);
>>> + return 0;
>>> +}
>>> +
>>> +static struct i2c_driver pca9641_driver = {
>>> + .driver = {
>>> + .name = "pca9641",
>>> + .of_match_table = of_match_ptr(pca9641_of_match),
>>> + },
>>> + .probe = pca9641_probe,
>>> + .remove = pca9641_remove,
>>> + .id_table = pca9641_id,
>>> +};
>>> +
>>> +module_i2c_driver(pca9641_driver);
>>> +
>>> +MODULE_AUTHOR("Ken Chen <chen.kenyy at inventec.com>");
>>> +MODULE_DESCRIPTION("PCA9641 I2C master demultiplexer driver");
>>> +MODULE_LICENSE("GPL v2");
>>> --
>>> 2.9.3
>>>
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