Re: [PATCH v2] can: sja1000 fix isr hang when hw is unplugged under load

[Wolfgang Grandegger <wg@grandegger.com>]

On 02/18/2012 06:00 PM, Marc Kleine-Budde wrote:
> On 02/18/2012 05:44 PM, Wolfgang Grandegger wrote:
>> On 02/18/2012 04:34 PM, Oliver Hartkopp wrote:
>>> On 18.02.2012 15:33, Wolfgang Grandegger wrote:
>>>
>>>> On 02/17/2012 09:27 PM, Marc Kleine-Budde wrote:
>>>>> On 02/15/2012 05:51 PM, Oliver Hartkopp wrote:
>>>>>> In the case of hotplug enabled devices (PCMCIA/PCIeC) the removal of the
>>>>>> hardware can cause an infinite loop in the common sja1000 isr.
>>>>>>
>>>>>> Use the already retrieved status register to indicate a possible hardware
>>>>>> removal and double check by reading the mode register in sja1000_is_absent.
>>>>>>
>>>>>> v2: Create a new function to not print information in irq context.
>>>>>>
>>>>>> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
>>>>>
>>>>> Thanks for the patch. I'm going to commit it to can-next. Any objections?
>>>>
>>>> Sorry for the late response but what is this double check good for? All
>>>> register reads will return 0xff if the card is unplugged. And if the
>>>> double check is OK we will continue even we have realized a clear
>>>> failure (status was 0xff).
>>>
>>>
>>> Hi Wolfgang,
>>>
>>> i checked the SJA1000 spec. The status register can potentially hold the value
>>> 0xFF by specification. So even when it's not very likely that it holds 0xFF -
>>> it can be. Additionally you may have SJA1000 FPGA cores that do not behave
>>> exactly like the SJA1000 itself.
>>>
>>> To double check the unlikely case i do a read on the mode register, which has
>>> some bits definitely set to "0" which is a strong indication for the
>>> controller removal.
>>
>> OK, no more objections. Hope to find some time soon to test my PCAN PCcard.
> 
> Can I add your Acked-by to the patch?

Yes. I do not expect any more problems.

Wolfgang.