From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philippe Reynes Subject: Re: [PATCH] imx27: dt: only map 1 Kbyte for fec registers Date: Wed, 13 May 2015 00:21:08 +0200 Message-ID: <55527CD4.6010208@gmail.com> References: <1431204870-17233-1-git-send-email-tremyfr@gmail.com> <20150511120101.GA25495@tiger> <55511E34.5040908@gmail.com> <20150512070117.GV12671@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20150512070117.GV12671@pengutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: =?ISO-8859-1?Q?Uwe_Kleine-K=F6nig?= Cc: Shawn Guo , mark.rutland@arm.com, devicetree@vger.kernel.org, linux@arm.linux.org.uk, pawel.moll@arm.com, ijc+devicetree@hellion.org.uk, linux-kernel@vger.kernel.org, robh+dt@kernel.org, kernel@pengutronix.de, galak@codeaurora.org, shawn.guo@linaro.org, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org Hi Uwe, On 12/05/15 09:01, Uwe Kleine-K=F6nig 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 >>>> --- >>>> 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/imx2= 7.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 =3D "fsl,imx27-fec"; >>>> - reg =3D<0x1002b000 0x4000>; >>>> + reg =3D<0x1002b000 0x400>; >>> >>> No. Per MCIMX27RM.pdf, Table 2-7. AIPI2 Memory Map, it should be 4= KiB. >> >> 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 t= he > 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 fi= rst > 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 leng= th > 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