Messages in this thread | | | Date | Tue, 21 Jul 2020 11:07:29 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCH] i2c: i2c-qcom-geni: Fix DMA transfer race |
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On 2020-07-21 05:54, 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> > --- > > drivers/i2c/busses/i2c-qcom-geni.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-qcom-geni.c > b/drivers/i2c/busses/i2c-qcom-geni.c > index 18d1e4fd4cf3..21e27f10510a 100644 > --- a/drivers/i2c/busses/i2c-qcom-geni.c > +++ b/drivers/i2c/busses/i2c-qcom-geni.c > @@ -366,15 +366,15 @@ static int geni_i2c_rx_one_msg(struct > geni_i2c_dev *gi2c, struct i2c_msg *msg, > else > geni_se_select_mode(se, GENI_SE_FIFO); > > - writel_relaxed(len, se->base + SE_I2C_RX_TRANS_LEN); > - geni_se_setup_m_cmd(se, I2C_READ, m_param); > - > if (dma_buf && geni_se_rx_dma_prep(se, dma_buf, len, &rx_dma)) { > geni_se_select_mode(se, GENI_SE_FIFO); > i2c_put_dma_safe_msg_buf(dma_buf, msg, false); > dma_buf = NULL; > } > > + writel_relaxed(len, se->base + SE_I2C_RX_TRANS_LEN); > + geni_se_setup_m_cmd(se, I2C_READ, m_param); > + > time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); > if (!time_left) > geni_i2c_abort_xfer(gi2c);
Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
-- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
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