On Wed, Jul 22, 2020 at 03:00:21PM -0700, 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 starting 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. > > Although problems were seen on the RX path, code inspection suggests > that the TX should be changed too. Change it as well. > > Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the Qualcomm GENI I2C controller") > Signed-off-by: Douglas Anderson > Tested-by: Sai Prakash Ranjan > Reviewed-by: Akash Asthana Applied to for-current, thanks!