linux-kernel - Re: [PATCH 1/4] phy: miphy365x: Add Device Tree bindings for the MiPHY365x

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Message-ID: <20140305084039.GB14902@lee--X1>
Date:	Wed, 5 Mar 2014 16:40:39 +0800
From:	Lee Jones <lee.jones@...aro.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alexandre.torgue@...com" <alexandre.torgue@...com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...com>
Subject: Re: [PATCH 1/4] phy: miphy365x: Add Device Tree bindings for the
 MiPHY365x

On Wed, 05 Mar 2014, Mark Rutland wrote:

> On Fri, Feb 14, 2014 at 11:23:53AM +0000, Lee Jones wrote:
> > The MiPHY365x is a Generic PHY which can serve various SATA or PCIe
> > devices. It has 2 ports which it can use for either; both SATA, both
> > PCIe or one of each in any configuration.
> > 
> > Cc: devicetree@...r.kernel.org
> > Cc: Srinivas Kandagatla <srinivas.kandagatla@...com>
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > ---
> >  .../devicetree/bindings/phy/phy-miphy365x.txt      | 54 ++++++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/phy/phy-miphy365x.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/phy/phy-miphy365x.txt b/Documentation/devicetree/bindings/phy/phy-miphy365x.txt
> > new file mode 100644
> > index 0000000..96f269f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/phy-miphy365x.txt
> > @@ -0,0 +1,54 @@
> > +STMicroelectronics STi MIPHY365x PHY binding
> > +============================================
> > +
> > +This binding describes a miphy device that is used to control PHY hardware
> > +for SATA and PCIe.
> > +
> > +Required properties:
> > +- compatible: Should be "st,miphy365x-phy"
> > +- #phy-cells: Should be 2 (See second example)
> > +		First cell is the port number; MIPHY_PORT_{0,1}
> > +		Second cell is device type; MIPHY_TYPE_{SATA,PCI}
> 
> Either this should refer to the header file, or specific values should
> be given in the binding document.

When you say specific values you mean break out the {,}s?

I thought most people would know what they mean.

> > +- reg:	      Address and length of the register set for the device
> > +- reg-names:  The names of the register addresses corresponding to the
> > +	      registers filled in "reg"
> > +		Options are; sata{0,1} and pcie{0,1} (See first example)
> 
> How about something like:

Same here.

> - reg: a list of offset + length pairs, one for each entry in reg-names
> - reg-names: should contain some of:
>   * "sata0" for ...
>   * "sata1" for ...
>   * "pcie0" for ...
>   * "pcie1" for ...
> 
> Where ... might just be "the sata port 0 registers"

Seems awfully redundant.

> > +- st,syscfg : Should be a phandle of the system configuration register group
> > +	      which contain the SATA, PCIe mode setting bits
> 
> I'll assume this is well-defined by some other binding.

Right.

> > +
> > +Optional properties:
> > +- st,sata-gen	     : Generation of locally attached SATA IP. Expected values
> > +		       are {1,2,3). If not supplied generation 1 hardware will
> > +		       be expected
> > +- st,pcie-tx-pol-inv : Bool property to invert the polarity PCIe Tx (Txn/Txp)
> > +- st,sata-tx-pol-inv : Bool property to invert the polarity SATA Tx (Txn/Txp)
> 
> It might just be me, but the phrase "invert the polarity {SATA,PCIe} Tx"
> sounds odd. What exactly is being inverted?

>From the doc (and the only reference of this functionallity):

rx_polarity:
  1: switch rxp/rxn
tx_polarity:
  1: switch txp/txn

If we don't set these registers up to reflect the h/w configuration of
the board, the MiPHY will not work.

> > +
> > +Example:
> > +
> > +	miphy365x_phy: miphy365x@0 {
> > +		compatible = "st,miphy365x-phy";
> > +		#phy-cells = <2>;
> > +		reg =	<0xfe382000 0x100>,
> > +			<0xfe38a000 0x100>,
> > +			<0xfe394000 0x100>,
> > +			<0xfe804000 0x100>;
> > +		reg-names = "sata0", "sata1", "pcie0", "pcie1";
> > +		st,syscfg= <&syscfg_rear>;
> 
> Nit: missing space before '='.

Will fix.

> > +	};
> > +
> > +Specifying phy control of devices
> > +=================================
> > +
> > +Device nodes should specify the configuration required in their "phys"
> > +property, containing a phandle to the miphy device node, a port number
> > +and a device type.
> > +
> > +Example:
> > +
> > +#include <dt-bindings/phy/phy-miphy365x.h>
> > +
> > +	sata0: sata@...80000 {
> > +		...
> > +		phys	  = <&miphy365x_phy MIPHY_PORT_0 MIPHY_TYPE_SATA>;
> > +		...
> > +	};
> 
> Is there not a generic phy binding we can point to? It seems a bit
> redundant to do this in each phy binding.

Sure, but that wouldn't make much of an example.

  Documentation/devicetree/bindings/phy/phy-bindings.txt

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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