linux-kernel - Re: Query: Phy: How to find consumer device on dt platform

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Date:	Wed, 29 Jan 2014 11:11:56 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Pratyush Anand <pratyush.anand@...com>,
	Mohit Kumar <mohit.kumar@...com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: Query: Phy: How to find consumer device on dt platform

Hi,

On Wednesday 29 January 2014 02:56 AM, Arnd Bergmann wrote:
> On Tuesday 28 January 2014, Kishon Vijay Abraham I wrote:
>>> I have a common set of registers, which need to be programmed
>>> differently for PCIe and SATA during phy init/exit.
>>
>> One way is differentiate using different compatible strings fro pcie and sata
>> and use of_device_is_compatible to select a particular path.
> 
> But if the IP block is the same, the compatible string should be
> identical.

Actually we define the compatible for 'device' no?. Here the same IP is
configured differently as different devices in SoCs.
> 
>>> Therefore, in the init/exit routine of phy_ops, I need some way of
>>> identifying that phy_init/exit has been called from PCIe driver or
>>> SATA driver.
>>
>> In this case you'll be actually registering two different PHYs (each for pcie
>> and sata), so your phy_get should give you the only the appropriate phy.
> 
> I would instead recommend making the mode of the PHY device the
> argument to the phy handle in DT, so that the sata node uses
> 
> 	phys = <&phyA 0>;
> 
> and the PCIe node uses
> 
> 	phys = <&phyB 1>;
> 
> Then the binding for the phy defines that an argument of '0' means sata mode,
> while '1' means pcie mode, plus you should define all other valid modes.

Anyway phyA and phyB points to different nodes and just from phyA and phyB we
should be able to tell whether it is sata or pcie.

We can just have a property in phyA to specify it is SATA and phyB to specify
it is PCIE.
phyA {
	compatible="phy-pipe3";
	.
	.
	type=<SATA>;
}
phyB {
	compatible="phy-pipe3";
	.
	.
	type=<PCIE>;
}
Then in probe
	of_property_read_u32(node, "type", &pipe3->type);

In phy_init function we can follow different path for SATA and PCIE using the type

static int pipe3_init(struct phy *x) {
	struct pipe3 *phy = phy_get_drvdata(x);

	switch (phy->type) {
	case SATA:
		/* do sata phy initialization here*/
		break;
	case PCIE:
		/* do pcie phy initialization here*/
		break;
	default:
		dev_err(phy->dev, "phy type not supported\n");
	}

	return 0;
}

Cheers
Kishon
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