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Message-ID: <20110810171600.GV4926@sgi.com>
Date: Wed, 10 Aug 2011 12:16:00 -0500
From: Robin Holt <holt@....com>
To: Kumar Gala <galak@...nel.crashing.org>
Cc: Robin Holt <holt@....com>,
Wood Scott-B07421 <B07421@...escale.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
U Bhaskar-B22300 <B22300@...escale.com>,
"socketcan-core@...ts.berlios.de" <socketcan-core@...ts.berlios.de>,
PPC list <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v10 5/5] [powerpc] Fix up fsl-flexcan device tree
binding.
On Wed, Aug 10, 2011 at 11:53:15AM -0500, Kumar Gala wrote:
>
> On Aug 10, 2011, at 11:00 AM, Robin Holt wrote:
>
> > On Wed, Aug 10, 2011 at 02:36:20PM +0000, U Bhaskar-B22300 wrote:
> >>
> >>
> >>> -----Original Message-----
> >>> From: Robin Holt [mailto:holt@....com]
> >>> Sent: Wednesday, August 10, 2011 7:46 PM
> >>> To: Wolfgang Grandegger
> >>> Cc: Robin Holt; Marc Kleine-Budde; U Bhaskar-B22300; Wood Scott-B07421;
> >>> netdev@...r.kernel.org; Kumar Gala; socketcan-core@...ts.berlios.de; PPC
> >>> list
> >>> Subject: Re: [PATCH v10 5/5] [powerpc] Fix up fsl-flexcan device tree
> >>> binding.
> >>>
> >>> On Wed, Aug 10, 2011 at 03:47:43PM +0200, Wolfgang Grandegger wrote:
> >>>> Hi Robin,
> >>>>
> >>>> On 08/10/2011 05:06 AM, Robin Holt wrote:
> >>>>> In working with the socketcan developers, we have come to the
> >>>>> conclusion the Documentation...fsl-flexcan.txt device tree
> >>>>> documentation needs to be cleaned up. The driver does not depend
> >>>>> upon any properties other
> >>>>
> >>>> Your first sentence could be misleading. Please just describe what the
> >>>> patch does and why, something like:
> >>>>
> >>>> "This patch cleans up the documentation of the device-tree binding for
> >>>> the Flexcan devices on Freescale's PowerPC and ARM cores. Extra
> >>>> properties are not needed as the frequency of the source clock is
> >>>> fixed..." and so on.
> >>>
> >>> I borrowed heavily from your message. ;)
> >>>
> >>>>> than the required properties so we are removing the file.
> >>>>> Additionally, the p1010*dts* files are not following the standard
> >>>>> for node naming in that they have a trailing -v1.0.
> >>>>
> >>>>> Signed-off-by: Robin Holt <holt@....com>
> >>>>> To: Marc Kleine-Budde <mkl@...gutronix.de>,
> >>>>> To: Wolfgang Grandegger <wg@...ndegger.com>,
> >>>>> To: U Bhaskar-B22300 <B22300@...escale.com>
> >>>>> To: Scott Wood <scottwood@...escale.com>
> >>>>> Cc: socketcan-core@...ts.berlios.de,
> >>>>> Cc: netdev@...r.kernel.org,
> >>>>> Cc: PPC list <linuxppc-dev@...ts.ozlabs.org>
> >>>>> Cc: Kumar Gala <galak@...nel.crashing.org>
> >>>>> ---
> >>>>> .../devicetree/bindings/net/can/fsl-flexcan.txt | 61 ----------
> >>> ----------
> >>>>> arch/powerpc/boot/dts/p1010rdb.dts | 8 ---
> >>>>> arch/powerpc/boot/dts/p1010si.dtsi | 8 +-
> >>>>> 3 files changed, 4 insertions(+), 73 deletions(-) delete mode
> >>>>> 100644 Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> >>>>>
> >>>>> diff --git
> >>>>> a/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> >>>>> b/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> >>>>> deleted file mode 100644
> >>>>> index 1a729f0..0000000
> >>>>> --- a/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> >>>>> +++ /dev/null
> >>>>> @@ -1,61 +0,0 @@
> >>>>> -CAN Device Tree Bindings
> >>>>> -------------------------
> >>>>> -2011 Freescale Semiconductor, Inc.
> >>>>> -
> >>>>> -fsl,flexcan-v1.0 nodes
> >>>>> ------------------------
> >>>>> -In addition to the required compatible-, reg- and
> >>>>> interrupt-properties, you can -also specify which clock source shall
> >>> be used for the controller.
> >>>>> -
> >>>>> -CPI Clock- Can Protocol Interface Clock
> >>>>> - This CLK_SRC bit of CTRL(control register) selects the clock source
> >>> to
> >>>>> - the CAN Protocol Interface(CPI) to be either the peripheral clock
> >>>>> - (driven by the PLL) or the crystal oscillator clock. The selected
> >>> clock
> >>>>> - is the one fed to the prescaler to generate the Serial Clock
> >>> (Sclock).
> >>>>> - The PRESDIV field of CTRL(control register) controls a prescaler
> >>> that
> >>>>> - generates the Serial Clock (Sclock), whose period defines the
> >>>>> - time quantum used to compose the CAN waveform.
> >>>>> -
> >>>>> -Can Engine Clock Source
> >>>>> - There are two sources for CAN clock
> >>>>> - - Platform Clock It represents the bus clock
> >>>>> - - Oscillator Clock
> >>>>> -
> >>>>> - Peripheral Clock (PLL)
> >>>>> - --------------
> >>>>> - |
> >>>>> - --------- -------------
> >>>>> - | |CPI Clock | Prescaler | Sclock
> >>>>> - | |---------------->| (1.. 256) |------------>
> >>>>> - --------- -------------
> >>>>> - | |
> >>>>> - -------------- ---------------------CLK_SRC
> >>>>> - Oscillator Clock
> >>>>> -
> >>>>> -- fsl,flexcan-clock-source : CAN Engine Clock Source.This property
> >>> selects
> >>>>> - the peripheral clock. PLL clock is fed to the
> >>>>> - prescaler to generate the Serial Clock (Sclock).
> >>>>> - Valid values are "oscillator" and "platform"
> >>>>> - "oscillator": CAN engine clock source is
> >>> oscillator clock.
> >>>>> - "platform" The CAN engine clock source is the bus
> >>> clock
> >>>>> - (platform clock).
> >>>>> -
> >>>>> -- fsl,flexcan-clock-divider : for the reference and system clock, an
> >>> additional
> >>>>> - clock divider can be specified.
> >>>>> -- clock-frequency: frequency required to calculate the bitrate for
> >>> FlexCAN.
> >>>>> -
> >>>>> -Note:
> >>>>> - - v1.0 of flexcan-v1.0 represent the IP block version for P1010
> >>> SOC.
> >>>>> - - P1010 does not have oscillator as the Clock Source.So the default
> >>>>> - Clock Source is platform clock.
> >>>>> -Examples:
> >>>>> -
> >>>>> - can0@...00 {
> >>>>> - compatible = "fsl,flexcan-v1.0";
> >>>>> - reg = <0x1c000 0x1000>;
> >>>>> - interrupts = <48 0x2>;
> >>>>> - interrupt-parent = <&mpic>;
> >>>>> - fsl,flexcan-clock-source = "platform";
> >>>>> - fsl,flexcan-clock-divqider = <2>;
> >>>>> - clock-frequency = <fixed by u-boot>;
> >>>>> - };
> >>>>
> >>>> Do we really want to drop the documentation for that binding. I think
> >>>> something like the following text would be still useful:
> >>>>
> >>>> ------------------------
> >>>> Flexcan CAN contoller on Freescale's ARM and PowerPC processors
> >>>>
> >>>> Required properties:
> >>>>
> >>>> - compatible : Should be "fsl,flexcan" and optionally
> >>>> "fsl,flexcan-<processor>"
> >>>> - reg : Offset and length of the register set for this device
> >>>> - interrupts : Interrupt tuple for this device
> >>>>
> >>>> Example:
> >>>>
> >>>> can@...00 {
> >>>> compatible = "fsl,p1010-flexcan", "fsl,flexcan";
> >>>> reg = <0x1c000 0x1000>;
> >>>> interrupts = <48 0x2>;
> >>>> interrupt-parent = <&mpic>;
> >>>> };
> >>>> -------------------------
> >>>
> >>> Done, except the
> >>>> compatible = "fsl,p1010-flexcan", "fsl,flexcan";
> >>>
> >>> line is
> >>> compatible = "fsl,flexcan", "fsl,flexcan-p1010";
> >>>
> >>>>
> >>>> What do you think?
> >>>>
> >>>>> diff --git a/arch/powerpc/boot/dts/p1010rdb.dts
> >>>>> b/arch/powerpc/boot/dts/p1010rdb.dts
> >>>>> index 6b33b73..d6a0bb2 100644
> >>>>> --- a/arch/powerpc/boot/dts/p1010rdb.dts
> >>>>> +++ b/arch/powerpc/boot/dts/p1010rdb.dts
> >>>>> @@ -169,14 +169,6 @@
> >>>>> };
> >>>>> };
> >>>>>
> >>>>> - can0@...00 {
> >>>>> - fsl,flexcan-clock-source = "platform";
> >>>>> - };
> >>>>> -
> >>>>> - can1@...00 {
> >>>>> - fsl,flexcan-clock-source = "platform";
> >>>>> - };
> >>>>> -
> >>>>> usb@...00 {
> >>>>> phy_type = "utmi";
> >>>>> };
> >>>>> diff --git a/arch/powerpc/boot/dts/p1010si.dtsi
> >>>>> b/arch/powerpc/boot/dts/p1010si.dtsi
> >>>>> index 7f51104..20c396d 100644
> >>>>> --- a/arch/powerpc/boot/dts/p1010si.dtsi
> >>>>> +++ b/arch/powerpc/boot/dts/p1010si.dtsi
> >>>>> @@ -141,19 +141,19 @@
> >>>>> };
> >>>>>
> >>>>> can0@...00 {
> >>>>> - compatible = "fsl,flexcan-v1.0";
> >>>>> + compatible = "fsl,p1010-flexcan",
> >>>>> + "fsl,flexcan";
> >>>>
> >>>> Does fit on one line.
> >>>>
> >>>>> reg = <0x1c000 0x1000>;
> >>>>> interrupts = <48 0x2>;
> >>>>> interrupt-parent = <&mpic>;
> >>>>> - fsl,flexcan-clock-divider = <2>;
> >>>>> };
> >>>>>
> >>>>> can1@...00 {
> >>>>> - compatible = "fsl,flexcan-v1.0";
> >>>>> + compatible = "fsl,p1010-flexcan",
> >>>>> + "fsl,flexcan";
> >>>>
> >>>> Ditto
> >>>>
> >>>>> reg = <0x1d000 0x1000>;
> >>>>> interrupts = <61 0x2>;
> >>>>> interrupt-parent = <&mpic>;
> >>>>> - fsl,flexcan-clock-divider = <2>;
> >>>>> };
> >>>>>
> >>>>> L2: l2-cache-controller@...00 {
> >>>>
> >>>> Please also correct the node names (not using the number suffix).
> >>>
> >>> So the node names should be
> >>> can@...00 {
> >>> can@...00 {
> >>> correct?
> >>>
> >> [Bhaskar] As there are two CAN controllers on P1010,So won't it be better
> >> to distinguish it by can0 and can1 instead by simple "can" ?
> >
> > It looks like the way to do that is to assign a label to those devices
> > and then associate the label with an alias. I have no idea how that
> > works under the hood, but it is the way other files are set up. Take a
> > look at arch/powerpc/boot/dts/bamboo.dts for how they define the serial
> > interfaces.
> >
> > Grant or Wolfgang, is that the right way to handle the concern about
> > names or does it have no practical effect with the Linux kernel?
>
> It has not effect. The label is just if you need to reference it via some other means.
Does the alias have an effect?
Robin
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