Re: [RFC PATCH 15/15] arm: dts: dra7: add sata node

[Sergei Shtylyov]

On 09/20/2013 02:19 PM, Roger Quadros wrote:

> > > From: Balaji T K <balajitk@xxxxxx>

> > > Add support for sata controller.

> > > [Roger Q] Clean up.

> > > CC: Benoit Cousson <bcousson@xxxxxxxxxxxx>
> > > Signed-off-by: Balaji T K <balajitk@xxxxxx>
> > > Signed-off-by: Roger Quadros <rogerq@xxxxxx>
> > > ---
> > >    arch/arm/boot/dts/dra7.dtsi |   49 +++++++++++++++++++++++++++++++++++++++++++
> > >    1 files changed, 49 insertions(+), 0 deletions(-)

> > > diff --git a/arch/arm/boot/dts/dra7.dtsi b/arch/arm/boot/dts/dra7.dtsi
> > > index ce9a0f0..545545d 100644
> > > --- a/arch/arm/boot/dts/dra7.dtsi
> > > +++ b/arch/arm/boot/dts/dra7.dtsi
> > > @@ -426,6 +426,55 @@
[...]

> > > +        sata: sata@4a141100 {
> > > +            compatible = "ti,sata";
> > > +            ti,hwmods = "sata";
> > > +            reg = <0x4a141100 0x7>;

   Not 0x8 BTW?

> > > +            #address-cells = <1>;
> > > +            #size-cells = <1>;
> > > +            ranges;
> > > +            dwc-ahci@4a140000 {

> >     Hm, ePAPR spec. [1] says that "the name of a node should be somewhat generic, reflecting the function of the device and not its precise programming model", so it looks like the name should be "sata" as well. I'm a bit at a loss here, not sure why you had to use the nested device nodes.

> ok. will fix it to sata.
> I've nested it because the wrapper registers are not part of the AHCI sata controller.
> They are TI specific registers for power management.
> Similar setup is on the USB controller. Please see omap_dwc3 node.

> But if you have better idea, please let me know.

    Don't know, it seems to me that you're over-complicating it by using the 
nested nodes. You could just have AHCI regs as a first tuple of the "regs" 
prop, and PM regs as a second tuple.

> > > +                  compatible = "snps,dwc-ahci";
> > > +                  reg = <0x4a140000 0x1100>;
> > > +                  interrupts = <0 54 0x4>;
> > > +                  phys = <&sata_phy>;

> >     Hm, it's the third PHY related generic property I'm encountering. First, there was "phy-handle", then "phy", now "phys"... Seems like a bit too much. :-)

> I'm afraid but this is how the designers have made it.

> 1) control-phy-pipe3 is that part of the PHY which sits in control module space and is different
> from the sata-phy space and hence needs a different node. If it were to me, I would just put this
> resource in sata-phy node, but there was a discussion about this earlier to do it otherwise [1].

> 2) sata-phy (sataphy) is the actual SATA PHY device.

> 3) phys is just a reference to the sata_phy and is used via the generic PHY framework.
> It is upto the sata driver to power up/down the phy.

   I understand that it's a reference but why have 3 variants of such phandle 
containing prop? Is it really possible for a device to have multiple PHYs? 
Well, remembering our customer's USB, it's indeed possible, however, there 2 
PHYs out of 3 are not software controllable...

> > > +                  phy-names = "sata-phy";
> > > +                  clocks = <&sata_ref_clk>;
> > > +                  clock-names = "optclk";
> > > +            };
> > > +        };

> > [1] http://www.power.org/resources/downloads/Power_ePAPR_APPROVED_v1.0.pdf

> cheers,
> -roger

> [1] - https://lkml.org/lkml/2012/9/10/399

WBR, Sergei

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