Re: [PATCH] [V3] Xilinx : Framebuffer Driver: Add PLB support and cleanup DCR

[Grant Likely <grant.likely@secretlab.ca>]

On Wed, Apr 15, 2009 at 10:44 AM, Stephen Neuendorffer
<stephen.neuendorffer@xilinx.com> wrote:
>
>
>> -----Original Message-----
>> From: Grant Likely [mailto:grant.likely@secretlab.ca]
>> Sent: Wednesday, April 15, 2009 9:03 AM
>> To: Stephen Neuendorffer
>> Cc: John Linn; jwboyer@linux.vnet.ibm.com; linux-fbdev-devel@lists.sourc=
eforge.net; linuxppc-
>> dev@ozlabs.org; akonovalov@ru.mvista.com; adaplas@gmail.com; Suneel Gara=
pati
>> Subject: Re: [PATCH] [V3] Xilinx : Framebuffer Driver: Add PLB support a=
nd cleanup DCR
>>
>> On Wed, Apr 15, 2009 at 9:58 AM, Stephen Neuendorffer
>> <stephen.neuendorffer@xilinx.com> wrote:
>> >> > - =A0 =A0 =A0 rc =3D of_address_to_resource(op->node, 0, &res);
>> >> > - =A0 =A0 =A0 if (rc) {
>> >> > - =A0 =A0 =A0 =A0 =A0 =A0 =A0 dev_err(&op->dev, "invalid address\n"=
);
>> >> > - =A0 =A0 =A0 =A0 =A0 =A0 =A0 return rc;
>> >> > + =A0 =A0 =A0 /*
>> >> > + =A0 =A0 =A0 =A0* To check whether the core is connected directly =
to DCR or PLB
>> >> > + =A0 =A0 =A0 =A0* interface and initialize the tft_access accordin=
gly.
>> >> > + =A0 =A0 =A0 =A0*/
>> >> > + =A0 =A0 =A0 p =3D (u32 *)of_get_property(op->node, "xlnx,dcr-splb=
-slave-if", NULL);
>> >>
>> >> Hmmm. =A0This binding is undocumented. =A0It would be better to make =
the
>> >> decision on the presence/absence of the dcr-reg and/or reg properties=
.
>> >
>> > For backward compatibility with the 'old' way, the device tree generat=
or for this core has both
>> dcr-reg and reg properties (where the reg has been translated back throu=
gh the bridge).
>>
>> So, what is in the regs and dcr-regs properties when DCR is used?
>>
>> How about when MMIO is used?
>>
>
> Currently:
> Core has DCR access, connected DCR bus:
> =A0 =A0 =A0 =A0device tree contains dcr-reg property.
> Core has DCR access, accessed through plb->dcr bridge:
> =A0 =A0 =A0 =A0device tree contains dcr-reg property, AND for backward co=
mpatibility with the
> =A0 =A0 =A0 =A0old driver, a reg property which contains the apparent reg=
isters on the bus.
> Core has PLB access:
> =A0 =A0 =A0 =A0device tree contains reg property only.
>
> So, I guess it really doesn't matter... The only interesting case is the =
second one where (because the way the reg property is published), either me=
thod will work... =A0So, nevermind, the device tree question is completely =
independent and I agree with your comment that there's probably not a need =
for a separate binding.
>
> What I do think would be nice (at some point in the future maybe) is perh=
aps a bit of DCR_or_PLB abstraction for this core and the ll_temac driver t=
o share which would avoid duplicating the code in each driver as to whether=
 it uses DCR or PLB access...

Good idea.

g.

>
> Steve
>
>
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--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.