Re: [PATCH V8 3/5] i2c: tegra: Add DMA Support

[Dmitry Osipenko]

31.01.2019 19:56, Sowjanya Komatineni ÐÐÑÐÑ:
> 
>>>>  drivers/i2c/busses/Kconfig     |   2 +-
>>>>  drivers/i2c/busses/i2c-tegra.c | 362 
>>>> ++++++++++++++++++++++++++++++++++++++---
>>>>  2 files changed, 339 insertions(+), 25 deletions(-)
>>>
>>> Tegra20 crashes because of this patch:
>>>
>> [snip]
>>> <4>[    3.395915] ------------[ cut here ]------------
>>> <2>[    3.395919] kernel BUG at drivers/i2c/busses/i2c-tegra.c:810!
>> The BUG line is from:
>>
>> 	if (status & I2C_INT_PACKET_XFER_COMPLETE) {
>> 		if (i2c_dev->is_curr_dma_xfer)
>> 			i2c_dev->msg_buf_remaining = 0;
>> 		BUG_ON(i2c_dev->msg_buf_remaining);
>> 		complete(&i2c_dev->msg_complete);
>> 	}
>>
> BUG_ON line is not part of this change. It was already there in existing driver.
> Based on log, I see DMA transfer is done for 224 bytes followed by 1 successful PIO transfer and then on next PIO transfer it received packet xfer complete interrupt with incomplete transfer bytes and that where it hit BUG_ON condition.
> 
> 

Yes, that BUG_ON is caused by the DMA transferring. Everything works fine be setting dma=false in the code, hence it's likely not a bug in the code (at least for now it looks fine), but likely that HW is not programmed correctly.