On Thu, Jul 23, 2020 at 09:56:34PM +0200, Wolfram Sang wrote: > 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! Glad we got this sorted. I just wondered that Alok wasn't part of the discussion. Is he still interested in maintaining the driver? Also because there is an unprocessed patch left for this driver: http://patchwork.ozlabs.org/project/linux-i2c/patch/20191103212204.13606-1-colin.king@canonical.com/