Messages in this thread | | | Subject | Re: [PATCH] i2c: i2c-qcom-geni: Fix DMA transfer race | From | Akash Asthana <> | Date | Tue, 21 Jul 2020 16:18:23 +0530 |
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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@chromium.org> > ---
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project
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