Re: [PATCH 2/2] i2c/designware: Provide optional i2c bus recovery function

[Vincenzo Frascino <vincenzo.frascino-qxv4g6HH51o@public.gmane.org>]

Hi Shubhrajyoti,

Il 27/02/2012 08:21, Shubhrajyoti Datta ha scritto:
> On Fri, Feb 24, 2012 at 5:01 PM, Viresh Kumar <viresh.kumar-qxv4g6HH51o@public.gmane.org> wrote:
>> From: Vincenzo Frascino <vincenzo.frascino-qxv4g6HH51o@public.gmane.org>
>>
>> Add optional i2c_recover_bus() function to the Synopsys DesignWare I2C adapter
>> driver that performs i2c bus recovery after timeout. The scope of this routine
>> is to define i2c bus recovery procedure as specified in the i2c protocol Rev. 03
>> section 3.16 titled "Bus clear".
> What do you do in the function ?
With this function we provide the bus clear procedure for i2c recovery as
described in the the i2c protocol Rev. 03 section 3.16 titled "Bus clear".
>
> Could we have it in the driver file itself?
As it is thought now, it's implementation depends a little bit from the platform
we are using, but, sure, it can be generalized and put into the driver.
>
>> Since the Designware I2C controller doesn't provide direct control over SDA and
>> SCL lines hence the intent is to let platform try to recover the bus if they
>> have the capability to take control of I2C pads and follow the recovery
>> protocol.
> So the function is passed in the pdata.
Yes, it is.
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino-qxv4g6HH51o@public.gmane.org>
>> Signed-off-by: Shiraz Hashim <shiraz.hashim-qxv4g6HH51o@public.gmane.org>
>> Signed-off-by: Viresh Kumar <viresh.kumar-qxv4g6HH51o@public.gmane.org>
>> ---
>>  drivers/i2c/busses/i2c-designware-core.c    |    4 +++
>>  drivers/i2c/busses/i2c-designware-core.h    |    3 +-
>>  drivers/i2c/busses/i2c-designware-platdrv.c |    8 ++++++
>>  include/linux/i2c/i2c-designware.h          |   33 +++++++++++++++++++++++++++
>>  4 files changed, 47 insertions(+), 1 deletions(-)
>>  create mode 100644 include/linux/i2c/i2c-designware.h
>>
>> diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
>> index df87992..91d9357 100644
>> --- a/drivers/i2c/busses/i2c-designware-core.c
>> +++ b/drivers/i2c/busses/i2c-designware-core.c
>> @@ -525,6 +525,10 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>>        ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete, HZ);
>>        if (ret == 0) {
>>                dev_err(dev->dev, "controller timed out\n");
>> +               if (dev->i2c_recover_bus) {
>> +                       dev_info(dev->dev, "try i2c bus recovery\n");
>> +                       dev->i2c_recover_bus(dev->recovery_data);
>> +               }
>>                i2c_dw_init(dev);
>>                ret = -ETIMEDOUT;
>>                goto done;
>> diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
>> index 02d1a2d..e2f3119 100644
>> --- a/drivers/i2c/busses/i2c-designware-core.h
>> +++ b/drivers/i2c/busses/i2c-designware-core.h
>> @@ -34,7 +34,6 @@
>>  #define DW_IC_CON_RESTART_EN           0x20
>>  #define DW_IC_CON_SLAVE_DISABLE                0x40
>>
>> -
>>  /**
>>  * struct dw_i2c_dev - private i2c-designware data
>>  * @dev: driver model device node
>> @@ -88,6 +87,8 @@ struct dw_i2c_dev {
>>        u32                     master_cfg;
>>        unsigned int            tx_fifo_depth;
>>        unsigned int            rx_fifo_depth;
>> +       void                    (*i2c_recover_bus)(void *);
>> +       void                    *recovery_data;
>>  };
>>
>>  extern u32 dw_readl(struct dw_i2c_dev *dev, int offset);
>> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
>> index c5ac2dc..2237398 100644
>> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
>> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
>> @@ -29,6 +29,7 @@
>>  #include <linux/module.h>
>>  #include <linux/delay.h>
>>  #include <linux/i2c.h>
>> +#include <linux/i2c/i2c-designware.h>
>>  #include <linux/clk.h>
>>  #include <linux/errno.h>
>>  #include <linux/sched.h>
>> @@ -55,6 +56,7 @@ static int __devinit dw_i2c_probe(struct platform_device *pdev)
>>        struct dw_i2c_dev *dev;
>>        struct i2c_adapter *adap;
>>        struct resource *mem, *ioarea;
>> +       struct i2c_dw_pdata *pdata;
>>        int irq, r;
>>
>>        /* NOTE: driver uses the static register mapping */
>> @@ -98,6 +100,12 @@ static int __devinit dw_i2c_probe(struct platform_device *pdev)
>>        }
>>        clk_enable(dev->clk);
>>
>> +       pdata = dev_get_platdata(&pdev->dev);
>> +       if (pdata && pdata->i2c_recover_bus) {
>> +               dev->i2c_recover_bus = pdata->i2c_recover_bus;
>> +               dev->recovery_data = &pdev;
>> +       }
>> +
>>        dev->functionality =
>>                I2C_FUNC_I2C |
>>                I2C_FUNC_10BIT_ADDR |
>> diff --git a/include/linux/i2c/i2c-designware.h b/include/linux/i2c/i2c-designware.h
>> new file mode 100644
>> index 0000000..e40ad85
>> --- /dev/null
>> +++ b/include/linux/i2c/i2c-designware.h
>> @@ -0,0 +1,33 @@
>> +/*
>> + * Synopsys DesignWare I2C adapter driver's platform data
>> + *
>> + * Copyright (C) 2012 ST Microelectronics.
>> + * Author: Vincenzo Frascino <vincenzo.frascino-qxv4g6HH51o@public.gmane.org>
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * 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.
>> + *
>> + */
>> +#ifndef I2C_DESIGNWARE_H
>> +#define I2C_DESIGNWARE_H
>> +
>> +#include <linux/platform_device.h>
>> +
>> +/* I2C Designware Platform Data */
>> +struct i2c_dw_pdata {
>> +       /*
>> +        * The scope of this routine is to define i2c bus recovery procedure
>> +        * as specified in the i2c protocol Rev. 03 section 3.16 titled
>> +        * "Bus clear".
>> +        * Its implementation is platform dependant.
>> +        */
>> +       void (*i2c_recover_bus)(void *);
>> +};
>> +
>> +#endif /* I2C_DESIGNWARE_H */
>> --
>> 1.7.8.110.g4cb5d
>>
>> --
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Thanks for the comments,

Vincenzo Frascino