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.
York
________________________________________
From: Stephen Boyd <sb...@codeaurora.org>
Sent: Monday, October 19, 2015 5:03 PM
To: Sun York-R58495
Cc: linux-clk@vger.kernel.org; pmarre...@outlook.com; Mike Turquette; Sebastian
Hesselbarth; Guenter Roeck; Andrey Filippov; Paul Bolle
Subject: Re: [Resend Patch v6] driver/clk/clk-si5338: Add common clock
framework driver for si5338
> Stephen,
>
> I am still having difficulty to implement this. The platform device doesn't
> know
> the clock device id when probing the clock chip. For my case, the platform
> device is a PCIe device, with I2C controller on it. The clock chip is on the
> I2C
> bus. When the PCIe device is probed, it registers the parent clocks for si5338
> before calling i2c_new_probed_device(). At this moment, the si5338 doesn't
> have
> an instance yet. So the parent clock pointer(s) in platform data structure
> is/are passed.
>
> I have another solution, let the platform data has clk pointer(s). The clock
> driver for si5338 will use device tree of_clk_get() if device tree is used, or
> take the pointer(s) from platform data. Upon driver removal, this driver call
> clk_put() regardless where the pointer(s) came from. The change will be in my
> platform device driver. It doesn't need to call clk_put again.
>
> Would it be acceptable?
Sorry I'm a little lost. Where does the platform data come into
the picture? Is the i2c driver going to the parent device to get
the platform data?
If we have a way to pass data to the si5338 i2c device, then I
assume we have a way to get the device name of the i2c device. If
that's true, then we can create a clk lookup structure with
clkdev_create() in the place where we have the clock pointer and
use the dev_name() of the i2c device as the third argument to
that function.
BTW, the i2c device doesn't need to call of_clk_get(), it can
just call clk_get() and pass the device pointer and it will use
the DT path if there's a provider. Please don't use of_clk_get()
when a struct device is present.
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