Messages in this thread | | | Subject | Re: [PATCH v2] i2c: i2c-qcom-geni: Fix DMA transfer race | From | "Mukesh, Savaliya" <> | Date | Thu, 23 Jul 2020 11:46:28 +0530 |
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On 7/23/2020 6:20 AM, Stephen Boyd wrote: > Quoting Douglas Anderson (2020-07-22 15:00:21) >> 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 <dianders@chromium.org> >> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> >> Reviewed-by: Akash Asthana <akashast@codeaurora.org> Reviewed-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org> >> --- > Reviewed-by: Stephen Boyd <swboyd@chromium.org>
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