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

Dmitry Osipenko
2019-01-31T17:25:54Z

31.01.2019 20:11, Dmitry Osipenko пишет:
> 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.
>

It works with this change:

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index fe5b89abc576..8e059e94b94e 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1170,10 +1170,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
time_left, completion_done(&i2c_dev->msg_complete),
i2c_dev->msg_err);

+ tegra_i2c_init(i2c_dev, true);
+
if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
return 0;

- tegra_i2c_init(i2c_dev, true);
/* start recovery upon arbitration loss in single master mode */
if (i2c_dev->msg_err == I2C_ERR_ARBITRATION_LOST) {
if (!i2c_dev->is_multimaster_mode)

Which means that HW state is kept dirty after DMA transfer. Please check everything carefully.