Hi Mr. Dooks,
On 5/2/2011 5:36 AM, Ben Dooks wrote:
> On Sat, Apr 23, 2011 at 01:31:35PM -0400, Michael Williamson wrote:
>> The davinci-i2c bus driver currently supports being probed with a NULL
>> platform_data structure by using a default configuration when none is
>> provided. However, the i2c_davinci_calc_clk_dividers does not
>> check the provided platform_data for NULL prior to using it, so
>> the support is incomplete.
>>
>> Rather than have each runtime call check for NULL and avoid future
>> problems, copy a pointer to the default data to the device structure
>> during the probe. This should be OK, as the information in this
>> structure is not modified by the driver.
>>
>> Tested on a MityDSP-L138 module (OMAP-L138 based SOM).
>>
>> Signed-off-by: Micahel Williamson <michael.williamson@xxxxxxxxxxxxxxxx>
>> ---
>> drivers/i2c/busses/i2c-davinci.c | 12 +++++-------
>> 1 files changed, 5 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
>> index 5795c83..1db8fc9 100644
>> --- a/drivers/i2c/busses/i2c-davinci.c
>> +++ b/drivers/i2c/busses/i2c-davinci.c
>> @@ -163,8 +163,7 @@ static void i2c_recover_bus(struct davinci_i2c_dev *dev)
>> flag |= DAVINCI_I2C_MDR_NACK;
>> /* write the data into mode register */
>> davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
>> - if (pdata)
>> - generic_i2c_clock_pulse(pdata->scl_pin);
>> + generic_i2c_clock_pulse(pdata->scl_pin);
>
> This looks like a change in the behaviour of the code, since if there was
> no pdata supplied we now can try generic_i2c_clock_pulse() with what is
> probably gpio pin 0.
>
- There is a check in generic_i2c_clock_pulse() that does not allow for scl_pin
pin = 0. I didn't realize gpio pin 0 was a valid gpio when looking at it. Seems
like this is an issue as well?
- I think this code is always getting called. I don't think there are any
platforms that would work using a NULL pdata as i2c_davinci_calc_clk_dividers
would bomb. I don't see any platforms in mach-davinci that provide NULL
i2c platform_data. Perhaps I'm not looking hard enough.
>> /* Send STOP */
>> flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
>> flag |= DAVINCI_I2C_MDR_STP;
>> @@ -235,10 +234,11 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
>> */
>> static int i2c_davinci_init(struct davinci_i2c_dev *dev)
>> {
>> - struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
>> + struct davinci_i2c_platform_data *pdata;
>>
>> - if (!pdata)
>> - pdata = &davinci_i2c_platform_data_default;
>> + if (!dev->dev->platform_data)
>> + dev->dev->platform_data = &davinci_i2c_platform_data_default;
>> + pdata = dev->dev->platform_data;
>
> Hmm, not going to work well if the driver is a module, as you'll unload
> the module, leave the default pointer in and then re-load later at a
> possibly different address with the old pointer in.
>
I hadn't thought of (or tested) the load->unload->reload scenario.
Subtle (well, to me anyway). Thanks for pointing that out. Appreciate
your cycles on review.
>> /* put I2C into reset */
>> davinci_i2c_reset_ctrl(dev, 0);
>> @@ -313,8 +313,6 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
>> u16 w;
>> int r;
>>
>> - if (!pdata)
>> - pdata = &davinci_i2c_platform_data_default;
>> /* Introduce a delay, required for some boards (e.g Davinci EVM) */
>> if (pdata->bus_delay)
>> udelay(pdata->bus_delay);
>> --
>> 1.7.0.4
>>
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