Re: [RFC 12/12] mipi-csis: Enable all interrupts for fimc-is usage

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

Hi Arun,

On 03/13/2013 05:09 AM, Arun Kumar K wrote:
> Hi Sylwester,
> 
>>>
>>>  /* Interrupt mask */
>>>  #define S5PCSIS_INTMSK                       0x10
>>> -#define S5PCSIS_INTMSK_EN_ALL                0xf000103f
>>> +#define S5PCSIS_INTMSK_EN_ALL                0xfc00103f
>>
>> Do you know what interrupts are assigned to the CSIS_INTMSK
>> bits 26, 27 ? In the documentation I have they are marked
>> as reserved. I have tested this patch on Exynos4x12, it seems
>> OK but you might want to merge it to the patch adding compatible
>> property for exynos5.
> 
> The bits 26 and 27 are for Frame start and Frame end interrupts.
> Yes this change can be merged with the MIPI-CSIS support for Exynos5.
> Shaik will pick it up and merge it along with his patch series in v2.

OK, thanks a lot for the clarification. I tested this patch on
Exynos4x12 and I could see twice as many interrupts from MIPI-CSIS as
there was captured frames from the sensor. Certainly we don't want to
see these interrupts when they are not needed. I have been thinking of
some interface that the MIPI-CSIS subdev would provide to the media
driver, so it can enable the interrupts when needed. I suppose a
private subdev ioctl might be good for that. But first I think there
is e.g. a subdev flag needed so a subdev driver can decide that it
doesn't want to have its non-standard ioctls called from user space.

I'll see if I can address those issues.

>> It would be good to know what these bits are for. And how
>> enabling the interrupts actually help without modifying the
>> interrupt handler ? Is it enough to just acknowledge those
>> interrupts ? Or how it works ?
>>
> 
> These interrupts are used by the FIMC-IS firmware possibly to check if the
> sensor is working. Without enabling these, I get the error from firmware
> on Sensor Open command.

Hm, interesting... Looks like the MIPI-CSIS interrupts get routed to the
FIMC-IS GIC. I was also wondering how the FIMC-IS receives Embedded Data
from the MIPI CSIS IP, which is sent by an image sensor. Presumably
FIMC-IS can memory map the Embedded Data buffer at the MIPI CSIS internal
memory, and then it reads from there. It's just a guess though.

Regards,
Sylwester