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SubjectRe: [PATCH V8 3/5] i2c: tegra: Add DMA Support
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31.01.2019 19:56, Sowjanya Komatineni пишет:
>
>>>> 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.

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