Re: [Resend Patch v6] driver/clk/clk-si5338: Add common clock framework driver for si5338

[York Sun <yorksun@freescale.com>]

On 10/19/2015 05:36 PM, Stephen Boyd wrote:
> On 10/20, York Sun wrote:
>> Sorry for top posting. I am on outlook web.
>>
>> We have no problem with device tree. Let's put it aside.
>>
>> When device is not used, the platform data is used to hold the data, filled by a platform device before probing the clock. For my case, the platform device is a PCIe device. It is a multifunction device with I2C controller on it. The pseudo code looks like
>>
>> struct i2c_board_info si5338_info[NUM_SI5338_CHIPS] = {
>>         {
>>                 .type = "si5338",
>>                 .platform_data = &si5338_pdata[0],
>>         },
>>         {
>>                 .type = "si5338",
>>                 .platform_data = &si5338_pdata[1],
>>         },
>>         {
>>                 .type = "si5338",
>>                 .platform_data = &si5338_pdata[2],
>>         },
>>         {
>>                 .type = "si5338",
>>                 .platform_data = &si5338_pdata[3],
>>         },
>> };
>> clk = clk_register_fixed_rate(&pdev->dev, "ref25", NULL, CLK_IS_ROOT, 25000000);
>> for (i = 0; i < NUM_SI5338_CHIPS; i++) {
>>     si5338_pdata[i].clk_xtal = clk;
>>     adap = i2c_get_adapter(private->i2c_adp->nr + 1 + i);
>>     private->i2c_client[i] = i2c_new_probed_device(adap, &si5338_info[i], i2c_si5338_addr, NULL);
>> }
>>
>> You can see, when the fixed-rate clock is registered, the device id of si5338 is unknown yet. (I am using one 25MHz clock to feed multiple si5338, where maybe I should create multiple 25MHz clocks, but that's another discussion.)
>>
>> I hope I have made it clear.
> 
> Yes. It would be great if we could modify the i2c framework to
> let us create an i2c device but not call device_register() until a later
> time. So something like this could be done in the platform
> driver:
> 
> 	for (i = 0; i < NUM_SI5338_CHIPS; i++) {
> 	     adap = i2c_get_adapter(private->i2c_adp->nr + 1 + i);
> 	     private->i2c_client[i] = i2c_new_device_unregistered(adap,
> 	     				&si5338_info[i], i2c_si5338_addr);
> 	     clkdev_create(clk, NULL, dev_name(private->i2c_client[i]->dev));
> 	     device_register(private->i2c_client[i]->dev);
> 	}
> 
> Then in the si5338 driver we call devm_clk_get(i2c->dev, NULL)
> and we get the xtal clock.
> 

Then what do we do before we have this i2c_new_device_unregistered()? Does my
proposal make sense?

York