On 7/21/2020 5:54 AM, Douglas Anderson wrote:
When I have KASAN enabled on my kernel and I start stressing the
touchscreen my system tends to hang. The touchscreen is one of the
only things that does a lot of big i2c transfers and ends up hitting
the DMA paths in the geni i2c driver. It appears that KASAN adds
enough delay in my system to tickle a race condition in the DMA setup
code.
When the system hangs, I found that it was running the geni_i2c_irq()
over and over again. It had these:
m_stat = 0x04000080
rx_st = 0x30000011
dm_tx_st = 0x00000000
dm_rx_st = 0x00000000
dma = 0x00000001
Notably we're in DMA mode but are getting M_RX_IRQ_EN and
M_RX_FIFO_WATERMARK_EN over and over again.
Putting some traces in geni_i2c_rx_one_msg() showed that when we
failed we were getting to the start of geni_i2c_rx_one_msg() but were
never executing geni_se_rx_dma_prep().
I believe that the problem here is that we are writing the transfer
length and setting up the geni command before we run
geni_se_rx_dma_prep(). If a transfer makes it far enough before we do
that then we get into the state I have observed. Let's change the
order, which seems to work fine.
Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the Qualcomm GENI I2C controller")
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
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Reviewed-by: Akash Asthana <akashast@xxxxxxxxxxxxxx>
--
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