Re: [PATCH linux dev-4.16] drivers: i2c: master arbiter: create driver

[ChenKenYY éæç TAO]

Hi all,
I had merged into i2c-mux-pca9541.c
It will be send out later.

2018-03-19 21:44 GMT+08:00 Guenter Roeck <linux@xxxxxxxxxxxx>:
> On 03/19/2018 05:45 AM, Peter Rosin wrote:
>>
>> Hi Ken,
>>
>> Thanks for the patch!
>>
>> I would have liked this subject:
>> i2c: muxes: pca9641: new driver
>>
>> On 2018-03-19 12:38, Ken Chen wrote:
>>>
>>> Initial PCA9641 2 chennel I2C bus master arbiter
>>
>>
>> channel
>>
>>> with separate implementation. It has probe issue
>>> and difference device hehavior between PCA9541
>>
>>
>> behavior
>>
>>> and PCA9641 in original PCA9641 patch.
>>>
>>> Signed-off-by: Ken Chen <chen.kenyy@xxxxxxxxxxxx>
>>> ---
>>>   drivers/i2c/muxes/Kconfig           |   9 +
>>>   drivers/i2c/muxes/Makefile          |   1 +
>>>   drivers/i2c/muxes/i2c-mux-pca9641.c | 360
>>> ++++++++++++++++++++++++++++++++++++
>>
>>
>> Given the big similarities between this and the pca9541 driver,
>> I would very much prefer if you could extend that driver instead
>> of making an almost-copy like this.
>>
>> I have added some comments below anyway, but most of them are
>> irrelevant given that I want this merged with the pca9541 driver.
>>
>> But maybe Guenter feels differently about that merge?
>>
>
> Same here. I didn't do a line-by-line comparison, but the code looks very
> similar.
> I did look into the probe function searching for differences after noticing
> "It has probe issue ...", but the difference there must be quite subtle
> since
> I didn't find it. The only real difference seems to be arbitration, but that
> can
> easily be added to the original driver as chip specific functions.
>
>
>>>   3 files changed, 370 insertions(+)
>>>   create mode 100644 drivers/i2c/muxes/i2c-mux-pca9641.c
>>>
>>> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
>>> index 52a4a92..f9c51b8 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 6d9d865..a229a1a 100644
>>> --- a/drivers/i2c/muxes/Makefile
>>> +++ b/drivers/i2c/muxes/Makefile
>>> @@ -12,6 +12,7 @@ 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..bcf45c8
>>> --- /dev/null
>>> +++ b/drivers/i2c/muxes/i2c-mux-pca9641.c
>>> @@ -0,0 +1,360 @@
>>> +/*
>>> + * I2C demultiplexer driver for PCA9641 bus master demultiplexer
>>> + *
>>> + * Copyright (c) 2010 Ericsson AB.
>>> + *
>>> + * Author: Ken Chen <chen.kenyy@xxxxxxxxxxxx>
>>
>>
>> A bit rich to claim to be the sole author, when you clearly "just"
>> modified the pca9541 driver. Please state the history!
>>
>
> And while retaining the original copyright.
>
>>> + *
>>> + * Derived from:
>>
>>
>> Maybe you intended to add something here, but forgot?
>>
>>> + *
>>> + * 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.
>>> + */
>
>
> New files should use the SPDX license identifier.
>
How can I use the SPDX license?
The previous license is GNU at i2c-mux-pca9541.c
>
>>> +
>>> +#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>
>>
>>
>> What is this last include for? We have moved away from specifying platform
>> data in (new) code.
Fixed
>>
>>> +
>>> +/*
>>> + * The PCA9641 is two I2C bus masters demultiplexer. It supports two I2C
>>> masters
>>
>>
>> "is two I2C bus masters" -> "is a two I2C bus master"
>>
>>> + * 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
>>
>>
>> winner
>>
>>> + * 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           BIT(0)
>>> +#define PCA9641_CTL_LOCK_GRANT         BIT(1)
>>> +#define PCA9641_CTL_BUS_CONNECT                BIT(2)
>>> +#define PCA9641_CTL_BUS_INIT           BIT(3)
>>> +#define PCA9641_CTL_SMBUS_SWRST                BIT(4)
>>> +#define PCA9641_CTL_IDLE_TIMER_DIS     BIT(5)
>>> +#define PCA9641_CTL_SMBUS_DIS          BIT(6)
>>> +#define PCA9641_CTL_PRIORITY           BIT(7)
>>> +
>>> +#define PCA9641_STS_OTHER_LOCK         BIT(0)
>>> +#define PCA9641_STS_BUS_INIT_FAIL      BIT(1)
>>> +#define PCA9641_STS_BUS_HUNG           BIT(2)
>>> +#define PCA9641_STS_MBOX_EMPTY         BIT(3)
>>> +#define PCA9641_STS_MBOX_FULL          BIT(4)
>>> +#define PCA9641_STS_TEST_INT           BIT(5)
>>> +#define PCA9641_STS_SCL_IO             BIT(6)
>>> +#define PCA9641_STS_SDA_IO             BIT(7)
>>> +
>>> +#define PCA9641_RES_TIME       0x03
>>> +
>>> +#define busoff(x, y)   (!((x) & PCA9641_CTL_LOCK_GRANT) && \
>>> +                       !((y) & PCA9641_STS_OTHER_LOCK))
>>> +#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" },
>>
>>
>> You need to describe the DT binding in
>> Documentation/devicetree/bindings/i2c
>> See nxp,pca9541.txt for inspiration.
>>
>>> +       {}
>>> +};
>>> +#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)
>>> +{
>>> +       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 (busoff(reg_ctl, reg_sts)) {
>>> +               /*
>>> +                * 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);
>>> +               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);
>>> +       }
>>> +       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;
>>
>>
>> Reading the data sheet, I noticed that the chip supports I2C device id.
>> There's a brand new function available in -next [1] that allows you to
>> check this. See the pca954x driver in -next for an example [2]. It checks
>> the I2C device id for the newer pca984x chips.
>>
>> [1]
>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/i2c/i2c-core-base.c
>> i2c_get_device_id(), currently circa line 2000
>>
>> [2]
>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/i2c/muxes/i2c-mux-pca954x.c
>>
Please help to review new patch the detect ID method.
>>> +       /*
>>> +        * 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),
>>
>>
>> Why 8? Should be 1, no?
Yes. should be 1.
>>
>>> +                            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);
>>> +
>>> +
>>
>>
>> Lose one of the empty lines here.
Fix
>>
>>> +       ret = i2c_mux_add_adapter(muxc, force, 0, 0);
>>> +       if (ret) {
>>> +               dev_err(&client->dev, "failed to register master
>>> demultiplexer\n");
>>
>>
>> This dev_err should go. i2c_mux_add_adapter provides a more
>> detailed error message on failure.
Removed and follow pca9541 probe code.
>>
>> Cheers,
>> Peter
>>
>>> +               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@xxxxxxxxxxxx>");
>>> +MODULE_DESCRIPTION("PCA9641 I2C master demultiplexer driver");
>>> +MODULE_LICENSE("GPL v2");
>>>
>>
>>
>