Re: [PATCH] imx27: dt: only map 1 Kbyte for fec registers

[Philippe Reynes]

Hi Uwe,

On 12/05/15 09:01, Uwe Kleine-König wrote:
> Hello,
>
> On Mon, May 11, 2015 at 11:25:08PM +0200, Philippe Reynes wrote:
> > On 11/05/15 14:01, Shawn Guo wrote:
> > > On Sat, May 09, 2015 at 10:54:30PM +0200, Philippe Reynes wrote:
> > > > According to the imx27 documentation, fec has a 1 Kbyte
> > > > memory space map, spitted in two regions of 512 bytes.
> > > > The first one for control/status registers, and the
> > > > second one for event/statistic registers. So, we don't
> > > > need to map 16 Kbyte for registers, 1 Kbyte is enough.
> > > >
> > > > Signed-off-by: Philippe Reynes<tremyfr@xxxxxxxxx>
> > > > ---
> > > >   arch/arm/boot/dts/imx27.dtsi |    2 +-
> > > >   1 files changed, 1 insertions(+), 1 deletions(-)
> > > >
> > > > diff --git a/arch/arm/boot/dts/imx27.dtsi b/arch/arm/boot/dts/imx27.dtsi
> > > > index 6951b66..56bb917 100644
> > > > --- a/arch/arm/boot/dts/imx27.dtsi
> > > > +++ b/arch/arm/boot/dts/imx27.dtsi
> > > > @@ -533,7 +533,7 @@
> > > >
> > > >   			fec: ethernet@1002b000 {
> > > >   				compatible = "fsl,imx27-fec";
> > > > -				reg =<0x1002b000 0x4000>;
> > > > +				reg =<0x1002b000 0x400>;
> > >
> > > No.  Per MCIMX27RM.pdf, Table 2-7. AIPI2 Memory Map, it should be 4KiB.
> >
> > I agree, this table show that 4KiB is reserved for fec registers.
> > But, in paragraph 29.6.1, there is :
> > "The FEC implementation requires a 1-Kbyte memory map space"
> > So I've thought that 1 Kbye is enough for the register memory space.
> The table 2-7 suggests that 4 KiB are routed to the fec even though the
> fec module might only make use of the first 1 KiB. That's no
> contradiction. The convention used in the device trees is that the first
> amount is used.

Ok, I understand, thanks for this explaination.

> > I'm pleased to understand that we're both agree that 16 Kbyte is too large.
> >
> > If you prefer 4 Kbyte, I'll send a v2 of this patch with this value.
> Yes please. In the commit log you might want to point out that a length
> of 16 KiB overlaps with the (currently unused?) Security Controller
> (SCC) of the i.MX27.

I've send a new patch (v2 and v3) that map 4 Kbyte for fec registers on imx27.

> Best regards
> Uwe

Best regards,
Philippe


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/