Date:	Wed, 10 Aug 2011 11:53:15 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Robin Holt <holt@....com>
Cc:	U Bhaskar-B22300 <B22300@...escale.com>,
	Wolfgang Grandegger <wg@...ndegger.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Wood Scott-B07421 <B07421@...escale.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"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 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.

- k--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists