[PATCH 2/4] can: flexcan: add hardware controller version support

[Wolfgang Grandegger]

Hi Marc,

On 06/27/2012 10:56 AM, Wolfgang Grandegger wrote:
> On 06/27/2012 10:27 AM, Marc Kleine-Budde wrote:
>> On 06/27/2012 10:19 AM, Hui Wang wrote:
>>> At least in the i.MX series, the flexcan contrller divides into ver_3
>>> and ver_10, current driver is for ver_3 controller.
>>>
>>> i.MX6 has ver_10 controller, it has more reigsters than ver_3 has.
>>> The rxfgmask (Rx FIFO Global Mask) register is one of the new added.
>>> Its reset value is 0xffffffff, this means ID Filter Table must be
>>> checked when receive a packet, but the driver is designed to accept
>>> everything during the chip start, we need to clear this register to
>>> follow this design.
>>>
>>> Add a hw_ver entry in the device tree, this can let us distinguish
>>> which version the controller is, if we don't set value to this entry,
>>> the hw_ver is 3 by default, this is backward compatible for existing
>>> platforms like powerpc and imx35.
>>
>> Is it possible to read this value from the hardware?
>> Another possibility would be to introduce a new compatible device in the
>> device tree.
> 
> I vote for the latter. IIRC, in the past we already had some discussion
> on how to handle version dependent Flexcan hardware, e.g. by using
> flexcan-vX.X or being expicit using fsl,p1010-flexcan. Search for "Add
> support for powerpc" in the netdev mailing list. I added the
> devicetree-discuss ml for that reason.

I looked up the threads and found:

  http://marc.info/?w=4&r=1&s=Fix+up+fsl-flexcan+device+tree+bi&q=t

In the Flexcan driver we currently only have:

  static struct of_device_id flexcan_of_match[] = {
        {
                .compatible = "fsl,p1010-flexcan",
        },
        {},
  };

What compatible string do they actually use for the i.MX6Q board? Shawn
or Hui? We need to fix that. From the discussion mentioned above I think
"fsl,flexcan-v10" would be acceptable. Unfortunately, we do not known
the internal version of the Flexcan controllers used in the various
PowerPC and ARM SOCs. We already realized some differences with
interrupts and bus error handling between i.MX28 and i.MX35. Would be
nice if someone (from Freescale?) could finally clarify that.

Wolfgang.