[PATCH v10 5/5] [powerpc] Fix up fsl-flexcan device tree binding.
Robin Holt
holt at sgi.com
Thu Aug 11 03:20:40 EST 2011
On Wed, Aug 10, 2011 at 12:17:45PM -0500, Kumar Gala wrote:
>
> On Aug 10, 2011, at 12:16 PM, Robin Holt wrote:
>
> > 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 at sgi.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 at vger.kernel.org; Kumar Gala; socketcan-core at lists.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 at sgi.com>
> >>>>>>> To: Marc Kleine-Budde <mkl at pengutronix.de>,
> >>>>>>> To: Wolfgang Grandegger <wg at grandegger.com>,
> >>>>>>> To: U Bhaskar-B22300 <B22300 at freescale.com>
> >>>>>>> To: Scott Wood <scottwood at freescale.com>
> >>>>>>> Cc: socketcan-core at lists.berlios.de,
> >>>>>>> Cc: netdev at vger.kernel.org,
> >>>>>>> Cc: PPC list <linuxppc-dev at lists.ozlabs.org>
> >>>>>>> Cc: Kumar Gala <galak at kernel.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 at 1c000 {
> >>>>>>> - 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 at 1c000 {
> >>>>>> 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 at 1c000 {
> >>>>>>> - fsl,flexcan-clock-source = "platform";
> >>>>>>> - };
> >>>>>>> -
> >>>>>>> - can1 at 1d000 {
> >>>>>>> - fsl,flexcan-clock-source = "platform";
> >>>>>>> - };
> >>>>>>> -
> >>>>>>> usb at 22000 {
> >>>>>>> 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 at 1c000 {
> >>>>>>> - 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 at 1d000 {
> >>>>>>> - 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 at 20000 {
> >>>>>>
> >>>>>> Please also correct the node names (not using the number suffix).
> >>>>>
> >>>>> So the node names should be
> >>>>> can at 1c000 {
> >>>>> can at 1d000 {
> >>>>> 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?
>
> nope
Then how does the device number get associated with a particular device
and how is user-space ensured a consistent namespace?
Robin
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