[PATCH v6] I2C: add CSR SiRFprimaII on-chip I2C controllers driver

[Barry Song]

hi Shubhrajyoti,

2012/2/17 Shubhrajyoti Datta <omaplinuxkernel at gmail.com>:
> Hello,
>
> On Wed, Feb 8, 2012 at 8:58 PM, Barry Song <21cnbao at gmail.com> wrote:
>> From: Zhiwu Song <Zhiwu.Song at csr.com>
>>
>> SiRFprimaII is the latest generation application processor from CSR’s
>> multi-function SoC product family.
>> The SoC support codes are in arch/arm/mach-prima2 from Linux mainline
>> 3.0.
>> There are two I2C controllers on primaII, features include:
>> * Two I2C controller modules are on chip
>> * RISC I/O bus read write register
>> * Up to 16 bytes data buffer for issuing commands and writing data
>>  at the same time
>> * Up to 16 commands, and receiving read data 16 bytes at a time
>> * Error INT report (ACK check)
>> * No-ACK bus protocols (SCCB bus protocols)
>>
>> Signed-off-by: Zhiwu Song <Zhiwu.Song at csr.com>
>> Signed-off-by: Xiangzhen Ye <Xiangzhen.Ye at csr.com>
>> Signed-off-by: Yuping Luo <Yuping.Luo at csr.com>
>> Signed-off-by: Barry Song <Baohua.Song at csr.com>
>> ---
>>  -v6:
>>  fix/cleanup lots of minor issues pointed out by wolfram;
>>  add OF property clock-frequency to support freq setting by DT;
>>  add lost devicetree binding document;
>>
>>  Documentation/devicetree/bindings/i2c/sirf-i2c.txt |   19 +
>>  drivers/i2c/busses/Kconfig                         |   10 +
>>  drivers/i2c/busses/Makefile                        |    1 +
>>  drivers/i2c/busses/i2c-sirf.c                      |  459 ++++++++++++++++++++
>>  4 files changed, 489 insertions(+), 0 deletions(-)
>>  create mode 100644 Documentation/devicetree/bindings/i2c/sirf-i2c.txt
>>  create mode 100644 drivers/i2c/busses/i2c-sirf.c
>>
>> diff --git a/Documentation/devicetree/bindings/i2c/sirf-i2c.txt b/Documentation/devicetree/bindings/i2c/sirf-i2c.txt
>> new file mode 100644
>> index 0000000..7baf9e1
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/i2c/sirf-i2c.txt
> <snip>
>
>> +
>> +               if (i2c_stat & SIRFSOC_I2C_STAT_NACK)
>> +                       dev_err(&siic->adapter.dev, "ACK not received\n");
> Could we send stop here?

no. when the interrupt happens and goes into the irq, the whole i2c hw
sequence has finished.

>> +               else
>> +                       dev_err(&siic->adapter.dev, "I2C error\n");
>> +
>> +               complete(&siic->done);
> <Snip>
>
>> +static int i2c_sirfsoc_resume(struct device *dev)
>> +{
>> +       struct platform_device *pdev = to_platform_device(dev);
>> +       struct i2c_adapter *adapter = platform_get_drvdata(pdev);
>> +       struct sirfsoc_i2c *siic = adapter->algo_data;
>> +
>> +       clk_enable(siic->clk);
>> +       writel(SIRFSOC_I2C_RESET, siic->base + SIRFSOC_I2C_CTRL);
> Could you explain why is a reset needed.
> Or am I missing something.

this is helping the i2c controller restore to a stable status. this
reset is not always needed, but it is sure that it can help to fix
some unstable issues of hardware if they do exist.

>
>> +       writel(SIRFSOC_I2C_CORE_EN | SIRFSOC_I2C_MASTER_MODE,
>> +               siic->base + SIRFSOC_I2C_CTRL);
>> +       writel(siic->clk_div, siic->base + SIRFSOC_I2C_CLK_CTRL);
>> +       writel(siic->sda_delay, siic->base + SIRFSOC_I2C_SDA_DELAY);
>> +       clk_disable(siic->clk);
>> +       return 0;
>> +}
>> +
>> +static const struct dev_pm_ops i2c_sirfsoc_pm_ops = {
>> +       .suspend = i2c_sirfsoc_suspend,
>> +       .resume = i2c_sirfsoc_resume,
> Could we use simple dev_pm ops here?

i guess you mean SIMPLE_DEV_PM_OPS. the only problem is i2c bus driver
doesn't need entries like:
 .freeze = suspend_fn, \
 .thaw = resume_fn, \
 .poweroff = suspend_fn, \
 .restore = resume_fn,

at least in our test, without these entries,  suspend to ram, suspend
to disk(hibernation) and poweroff have always worked well.

>
>> +};
>> +#endif
>> +
>> +static const struct of_device_id sirfsoc_i2c_of_match[] __devinitconst = {
>> +       { .compatible = "sirf,prima2-i2c", },

-barry